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 <li class="toctree-l1 current"><a class="reference internal" href="index.html">Introduction</a><ul class="current">
 <li class="toctree-l2"><a class="reference internal" href="about.html">About Apache NuttX</a></li>
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 <li class="toctree-l2 current"><a class="current reference internal" href="#">Resources</a><ul>
 <li class="toctree-l3"><a class="reference internal" href="#legacy-readme">Legacy README</a></li>
 <li class="toctree-l3"><a class="reference internal" href="#apache-nuttx">APACHE NUTTX</a></li>
 <li class="toctree-l3"><a class="reference internal" href="#introduction">INTRODUCTION</a></li>
 <li class="toctree-l3"><a class="reference internal" href="#community">COMMUNITY</a><ul>
 <li class="toctree-l4"><a class="reference internal" href="#getting-help">Getting Help</a></li>
 <li class="toctree-l4"><a class="reference internal" href="#mailing-lists">Mailing Lists</a></li>
 <li class="toctree-l4"><a class="reference internal" href="#reporting-security-issues">Reporting Security Issues</a></li>
 <li class="toctree-l4"><a class="reference internal" href="#issue-tracker">Issue Tracker</a><ul>
 <li class="toctree-l5"><a class="reference internal" href="#bug-reports">Bug Reports:</a></li>
 <li class="toctree-l5"><a class="reference internal" href="#feature-requests">Feature Requests:</a></li>
 </ul>
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 <li class="toctree-l4"><a class="reference internal" href="#source-code">Source Code</a></li>
 <li class="toctree-l4"><a class="reference internal" href="#website-source-code">Website Source Code</a></li>
 </ul>
 </li>
 <li class="toctree-l3"><a class="reference internal" href="#environments">ENVIRONMENTS</a><ul>
 <li class="toctree-l4"><a class="reference internal" href="#installing-cygwin">Installing Cygwin</a></li>
 <li class="toctree-l4"><a class="reference internal" href="#using-msys">Using MSYS</a></li>
 <li class="toctree-l4"><a class="reference internal" href="#ubuntu-bash-under-windows-10">Ubuntu Bash under Windows 10</a><ul>
 <li class="toctree-l5"><a class="reference internal" href="#installation-for-ubuntu-bash-under-windows-10">Installation for Ubuntu Bash under Windows 10</a></li>
 <li class="toctree-l5"><a class="reference internal" href="#accessing-windows-files-from-ubuntu">Accessing Windows Files from Ubuntu</a></li>
 <li class="toctree-l5"><a class="reference internal" href="#accessing-ubuntu-files-from-windows">Accessing Ubuntu Files From Windows</a></li>
 <li class="toctree-l5"><a class="reference internal" href="#executing-windows-tools-from-ubuntu">Executing Windows Tools from Ubuntu</a></li>
 <li class="toctree-l5"><a class="reference internal" href="#install-ubuntu-software">Install Ubuntu Software</a></li>
 <li class="toctree-l5"><a class="reference internal" href="#integrating-with-windows-tools">Integrating with Windows Tools</a></li>
 <li class="toctree-l5"><a class="reference internal" href="#graphics-support">Graphics Support</a></li>
 <li class="toctree-l5"><a class="reference internal" href="#using-macos">Using macOS</a></li>
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 <li class="toctree-l3"><a class="reference internal" href="#installation">INSTALLATION</a><ul>
 <li class="toctree-l4"><a class="reference internal" href="#download-and-unpack">Download and Unpack</a></li>
 <li class="toctree-l4"><a class="reference internal" href="#semi-optional-apps-package">Semi-Optional apps/ Package</a></li>
 <li class="toctree-l4"><a class="reference internal" href="#installation-directories-with-spaces-in-the-path">Installation Directories with Spaces in the Path</a></li>
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 <li class="toctree-l5"><a class="reference internal" href="#configuring-the-clones">Configuring the Clones</a></li>
 <li class="toctree-l5"><a class="reference internal" href="#cloning-nuttx-inside-cygwin">Cloning NuttX Inside Cygwin</a></li>
 </ul>
 </li>
 <li class="toctree-l4"><a class="reference internal" href="#related-repositories">Related Repositories</a></li>
 <li class="toctree-l4"><a class="reference internal" href="#notes-about-header-files">Notes about Header Files</a><ul>
 <li class="toctree-l5"><a class="reference internal" href="#other-c-library-header-files">Other C-Library Header Files</a></li>
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 <li class="toctree-l5"><a class="reference internal" href="#math-h">math.h</a></li>
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 </ul>
 </li>
 <li class="toctree-l3"><a class="reference internal" href="#configuring-nuttx">CONFIGURING NUTTX</a><ul>
 <li class="toctree-l4"><a class="reference internal" href="#instantiating-canned-configurations">Instantiating “Canned” Configurations</a><ul>
 <li class="toctree-l5"><a class="reference internal" href="#configure-sh-and-configure-bat"><code class="docutils literal notranslate"><span class="pre">configure.sh</span></code> and <code class="docutils literal notranslate"><span class="pre">configure.bat</span></code></a></li>
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 <li class="toctree-l4"><a class="reference internal" href="#finding-selections-in-the-configuration-menus">Finding Selections in the Configuration Menus</a></li>
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 <li class="toctree-l4"><a class="reference internal" href="#make-sure-that-you-are-on-the-right-platform">Make Sure that You are on the Right Platform</a></li>
 <li class="toctree-l4"><a class="reference internal" href="#comparing-two-configurations">Comparing Two Configurations</a></li>
 <li class="toctree-l4"><a class="reference internal" href="#making-defconfig-files">Making <code class="docutils literal notranslate"><span class="pre">defconfig</span></code> Files</a><ul>
 <li class="toctree-l5"><a class="reference internal" href="#config-files-as-defconfig-files"><code class="docutils literal notranslate"><span class="pre">.config</span></code> Files as <code class="docutils literal notranslate"><span class="pre">defconfig</span></code> Files:</a></li>
 <li class="toctree-l5"><a class="reference internal" href="#finding-the-apps-directory-path">Finding the <code class="docutils literal notranslate"><span class="pre">apps/</span></code> Directory Path:</a></li>
 <li class="toctree-l5"><a class="reference internal" href="#compressed-defconfig-files">Compressed <code class="docutils literal notranslate"><span class="pre">defconfig</span></code> Files:</a></li>
 <li class="toctree-l5"><a class="reference internal" href="#configuring-with-compressed-defconfig-files">Configuring with “Compressed” defconfig Files:</a></li>
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 <li class="toctree-l4"><a class="reference internal" href="#incompatibilities-with-older-configurations">Incompatibilities with Older Configurations</a></li>
 <li class="toctree-l4"><a class="reference internal" href="#nuttx-configuration-tool-under-dos">NuttX Configuration Tool under DOS</a></li>
 </ul>
 </li>
 <li class="toctree-l3"><a class="reference internal" href="#toolchains">TOOLCHAINS</a><ul>
 <li class="toctree-l4"><a class="reference internal" href="#cross-development-toolchains">Cross-Development Toolchains</a></li>
 <li class="toctree-l4"><a class="reference internal" href="#nuttx-buildroot-toolchain">NuttX Buildroot Toolchain</a></li>
 </ul>
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 <li class="toctree-l3"><a class="reference internal" href="#shells">SHELLS</a></li>
 <li class="toctree-l3"><a class="reference internal" href="#building-nuttx">BUILDING NUTTX</a><ul>
 <li class="toctree-l4"><a class="reference internal" href="#building">Building</a></li>
 <li class="toctree-l4"><a class="reference internal" href="#re-building">Re-building</a></li>
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 <li class="toctree-l5"><a class="reference internal" href="#build-targets">Build Targets</a></li>
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 <li class="toctree-l4"><a class="reference internal" href="#recovering-from-bad-configurations">Recovering from Bad Configurations</a></li>
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 <li class="toctree-l1"><a class="reference internal" href="inviolables.html">The Inviolable Principles of NuttX</a></li>
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   <section id="resources">
 <h1>Resources<a class="headerlink" href="#resources" title="Permalink to this heading"></a></h1>
 <div class="admonition note">
 <p class="admonition-title">Note</p>
 <p>this should be revised</p>
 </div>
 <p>Here’s a list of Apache NuttX resources that you might find helpful:</p>
 <blockquote>
 <div><ul class="simple">
 <li><p>Apache NuttX</p>
 <ul>
 <li><p><a class="reference external" href="https://nuttx.apache.org">Apache NuttX website</a></p></li>
 <li><p><a class="reference external" href="https://cwiki.apache.org/confluence/display/NUTTX/Nuttx">Apache NuttX online documentation</a></p></li>
 <li><p><a class="reference external" href="https://nuttx.apache.org/community/">Apache NuttX mailing list</a> – a very active mailing list, the place to get help with your application or any questions you have about NuttX.</p></li>
 <li><p><a class="reference external" href="https://www.youtube.com/channel/UC0QciIlcUnjJkL5yJJBmluw/videos">Apache NuttX YouTube channel</a> – Alan Carvalho de Assis’s YouTube channel on NuttX. It’s a source of a lot of great practical information.</p></li>
 <li><p><a class="reference external" href="https://cwiki.apache.org/confluence/display/NUTTX/Coding+Standard">Apache NuttX Coding Standard</a> — How code should look when you submit new files or modify existing ones.</p></li>
 <li><p><a class="reference external" href="https://cwiki.apache.org/confluence/display/NUTTX/Code+Contribution+Workflow">Apache NuttX Code Contribution Guidelines</a> — The full workflow to follow for submitting code with all the details.</p></li>
 </ul>
 </li>
 <li><p>Git</p>
 <ul>
 <li><p><a class="reference external" href="https://github.github.com/training-kit/downloads/github-git-cheat-sheet.pdf">Git Cheat Sheet (by GitHub)</a></p></li>
 <li><p><a class="reference external" href="https://git-scm.com/book/en/v2">Git Book (online)</a></p></li>
 </ul>
 </li>
 </ul>
 </div></blockquote>
 <section id="legacy-readme">
 <h2>Legacy README<a class="headerlink" href="#legacy-readme" title="Permalink to this heading"></a></h2>
 </section>
 <section id="apache-nuttx">
 <h2>APACHE NUTTX<a class="headerlink" href="#apache-nuttx" title="Permalink to this heading"></a></h2>
 <ul class="simple">
 <li><p>Introduction</p></li>
 <li><p>Community</p>
 <ul>
 <li><p>Getting Help</p></li>
 <li><p>Mailing Lists</p></li>
 <li><p>Issue Tracker</p></li>
 <li><p>Source Code</p></li>
 <li><p>Website Source Code</p></li>
 </ul>
 </li>
 <li><p>Environments</p>
 <ul>
 <li><p>Installing Cygwin</p></li>
 <li><p>Ubuntu Bash under Windows 10</p></li>
 <li><p>Using macOS</p></li>
 </ul>
 </li>
 <li><p>Installation</p>
 <ul>
 <li><p>Download and Unpack</p></li>
 <li><p>Semi-Optional apps/ Package</p></li>
 <li><p>Installation Directories with Spaces in the Path</p></li>
 <li><p>Downloading from Repositories</p></li>
 <li><p>Related Repositories</p></li>
 <li><p>Notes about Header Files</p></li>
 </ul>
 </li>
 <li><p>Configuring NuttX</p>
 <ul>
 <li><p>Instantiating “Canned” Configurations</p></li>
 <li><p>Refreshing Configurations</p></li>
 <li><p>NuttX Configuration Tool</p></li>
 <li><p>Finding Selections in the Configuration Menus</p></li>
 <li><p>Reveal Hidden Configuration Options</p></li>
 <li><p>Make Sure that You are on the Right Platform</p></li>
 <li><p>Comparing Two Configurations</p></li>
 <li><p>Making defconfig Files</p></li>
 <li><p>Incompatibilities with Older Configurations</p></li>
 <li><p>NuttX Configuration Tool under DOS</p></li>
 </ul>
 </li>
 <li><p>Toolchains</p>
 <ul>
 <li><p>Cross-Development Toolchains</p></li>
 <li><p>NuttX Buildroot Toolchain</p></li>
 </ul>
 </li>
 <li><p>Shells</p></li>
 <li><p>Building NuttX</p>
 <ul>
 <li><p>Building</p></li>
 <li><p>Re-building</p></li>
 <li><p>Build Targets and Options</p></li>
 <li><p>Native Windows Build</p></li>
 <li><p>Installing GNUWin32</p></li>
 </ul>
 </li>
 <li><p>Cygwin Build Problems</p>
 <ul>
 <li><p>Strange Path Problems</p></li>
 <li><p>Window Native Toolchain Issues</p></li>
 </ul>
 </li>
 <li><p>Documentation</p></li>
 </ul>
 </section>
 <section id="introduction">
 <h2>INTRODUCTION<a class="headerlink" href="#introduction" title="Permalink to this heading"></a></h2>
 <p>Apache NuttX is a real-time operating system (RTOS) with an emphasis on
 standards compliance and small footprint. Scalable from 8-bit to 64-bit
 microcontroller environments, the primary governing standards in NuttX are
 POSIX and ANSI standards. Additional standard APIs from Unix and other
 common RTOSs (such as VxWorks) are adopted for functionality not available
 under these standards, or for functionality that is not appropriate for
 deeply-embedded environments (such as fork()).</p>
 <dl class="simple">
 <dt>Extensive documentation can be found on the project wiki:</dt><dd><p><a class="reference external" href="https://cwiki.apache.org/NUTTX/NuttX">https://cwiki.apache.org/NUTTX/NuttX</a></p>
 </dd>
 </dl>
 <p>For brevity, many parts of the documentation will refer to Apache NuttX as
 simply NuttX.</p>
 </section>
 <section id="community">
 <h2>COMMUNITY<a class="headerlink" href="#community" title="Permalink to this heading"></a></h2>
 <p>Every volunteer project obtains its strength from the people involved in
 it.  We invite you to participate as much or as little as you choose.</p>
 <p>We encourage you to:</p>
 <ul class="simple">
 <li><p>Use our project and provide feedback.</p></li>
 <li><p>Provide us with use-cases.</p></li>
 <li><p>Report bugs and submit patches.</p></li>
 <li><p>Contribute code or documentation.</p></li>
 </ul>
 <section id="getting-help">
 <h3>Getting Help<a class="headerlink" href="#getting-help" title="Permalink to this heading"></a></h3>
 <p>The best place to get help is the developer’s mailing list.  Please see
 the following section:</p>
 </section>
 <section id="mailing-lists">
 <h3>Mailing Lists<a class="headerlink" href="#mailing-lists" title="Permalink to this heading"></a></h3>
 <p>Get help using NuttX or contribute to the project on our mailing lists:</p>
 <ul class="simple">
 <li><p><a class="reference external" href="mailto:dev&#37;&#52;&#48;nuttx&#46;apache&#46;org">dev<span>&#64;</span>nuttx<span>&#46;</span>apache<span>&#46;</span>org</a> is for people who want to contribute code to NuttX.</p>
 <ul>
 <li><p>To subscribe, send an email to <a class="reference external" href="mailto:dev-subscribe&#37;&#52;&#48;nuttx&#46;apache&#46;org">dev-subscribe<span>&#64;</span>nuttx<span>&#46;</span>apache<span>&#46;</span>org</a>.</p></li>
 <li><p>To unsubscribe, send an email to <a class="reference external" href="mailto:dev-unsubscribe&#37;&#52;&#48;nuttx&#46;apache&#46;org">dev-unsubscribe<span>&#64;</span>nuttx<span>&#46;</span>apache<span>&#46;</span>org</a>.</p></li>
 <li><p>View the archives at:
 <a class="reference external" href="https://www.mail-archive.com/dev&#64;nuttx.apache.org/">https://www.mail-archive.com/dev&#64;nuttx.apache.org/</a></p></li>
 </ul>
 </li>
 <li><p><a class="reference external" href="mailto:commits&#37;&#52;&#48;nuttx&#46;apache&#46;org">commits<span>&#64;</span>nuttx<span>&#46;</span>apache<span>&#46;</span>org</a> is a read-only list that notifies subscribers
 about commit messages and patches to NuttX.</p>
 <ul>
 <li><p>To subscribe, send an email to <a class="reference external" href="mailto:commits-subscribe&#37;&#52;&#48;nuttx&#46;apache&#46;org">commits-subscribe<span>&#64;</span>nuttx<span>&#46;</span>apache<span>&#46;</span>org</a>.</p></li>
 <li><p>To unsubscribe, send an email to <a class="reference external" href="mailto:commits-unsubscribe&#37;&#52;&#48;nuttx&#46;apache&#46;org">commits-unsubscribe<span>&#64;</span>nuttx<span>&#46;</span>apache<span>&#46;</span>org</a>.</p></li>
 <li><p>View the archives at:
 <a class="reference external" href="https://www.mail-archive.com/commits&#64;nuttx.apache.org/">https://www.mail-archive.com/commits&#64;nuttx.apache.org/</a></p></li>
 </ul>
 </li>
 </ul>
 </section>
 <section id="reporting-security-issues">
 <h3>Reporting Security Issues<a class="headerlink" href="#reporting-security-issues" title="Permalink to this heading"></a></h3>
 <p>Found a vulnerability? See our security policy <a class="reference external" href=".github/SECURITY.md">here</a>.</p>
 </section>
 <section id="issue-tracker">
 <h3>Issue Tracker<a class="headerlink" href="#issue-tracker" title="Permalink to this heading"></a></h3>
 <section id="bug-reports">
 <h4>Bug Reports:<a class="headerlink" href="#bug-reports" title="Permalink to this heading"></a></h4>
 <p>Found bug? Send an email to the dev list: <a class="reference external" href="mailto:dev&#37;&#52;&#48;nuttx&#46;apache&#46;org">dev<span>&#64;</span>nuttx<span>&#46;</span>apache<span>&#46;</span>org</a></p>
 <p>Before submitting an issue, please:</p>
 <ul class="simple">
 <li><p>Verify that the bug does in fact exist.</p></li>
 <li><p>Search the mailing list archives to verify there is no existing issue
 reporting the bug you’ve found.</p></li>
 <li><p>Consider tracking down the bug yourself in the NuttX source code and
 submitting a patch along with your bug report.  This is a great time
 saver for the NuttX developers and helps ensure the bug will be fixed
 quickly.</p></li>
 </ul>
 </section>
 <section id="feature-requests">
 <h4>Feature Requests:<a class="headerlink" href="#feature-requests" title="Permalink to this heading"></a></h4>
 <p>Enhancement requests for new features are also welcome. The more concrete
 and rational the request is, the greater the chance it will incorporated
 into future releases.</p>
 </section>
 </section>
 <section id="source-code">
 <h3>Source Code<a class="headerlink" href="#source-code" title="Permalink to this heading"></a></h3>
 <p>The project sources are in two Git repositories.  The core OS is in nuttx
 and the apps repository is in nuttx-apps.  These are housed in GitBox on
 ASF servers and also mirrored at GitHub.  These are kept in sync, so you
 can use whichever option you prefer.</p>
 <ul class="simple">
 <li><p>NuttX core OS repository:</p>
 <ul>
 <li><p>Primary:
 <a class="reference external" href="https://gitbox.apache.org/repos/asf?p=nuttx.git">https://gitbox.apache.org/repos/asf?p=nuttx.git</a></p></li>
 <li><p>GitHub Mirror:
 <a class="reference external" href="https://github.com/apache/nuttx">https://github.com/apache/nuttx</a></p></li>
 </ul>
 </li>
 <li><p>Apps repository:</p>
 <ul>
 <li><p>Primary:
 <a class="reference external" href="https://gitbox.apache.org/repos/asf?p=nuttx-apps.git">https://gitbox.apache.org/repos/asf?p=nuttx-apps.git</a></p></li>
 <li><p>GitHub Mirror:
 <a class="reference external" href="https://github.com/apache/nuttx-apps">https://github.com/apache/nuttx-apps</a></p></li>
 </ul>
 </li>
 </ul>
 </section>
 <section id="website-source-code">
 <h3>Website Source Code<a class="headerlink" href="#website-source-code" title="Permalink to this heading"></a></h3>
 <dl class="simple">
 <dt>The project website sources are accessible via the website source code</dt><dd><p>repository which is also mirrored in GitHub:</p>
 </dd>
 </dl>
 <ul class="simple">
 <li><p>Primary:
 <a class="reference external" href="https://gitbox.apache.org/repos/asf?p=nuttx-website.git">https://gitbox.apache.org/repos/asf?p=nuttx-website.git</a></p></li>
 <li><p>GitHub Mirror:
 <a class="reference external" href="https://github.com/apache/nuttx-website">https://github.com/apache/nuttx-website</a></p></li>
 </ul>
 </section>
 </section>
 <section id="environments">
 <h2>ENVIRONMENTS<a class="headerlink" href="#environments" title="Permalink to this heading"></a></h2>
 <blockquote>
 <div><p>NuttX requires a POSIX development environment such as you would find under
 Linux or macOS.  NuttX may also be installed and built on Windows system
 if you also provide such a POSIX development environment.  Options for a
 POSIX development environment under Windows include:</p>
 </div></blockquote>
 <ul>
 <li><p>An installation of Linux on a virtual machine (VM) in Windows.  I have
 not been happy using a VM myself.  I have had stability problems with
 open source VMs and commercial VMs cost more than I want to spend.
 Sharing files with Linux running in a VM is awkward;  sharing devices
 connected to the Windows box with Linux in a VM is, at the very least,
 confusing;  Using Windows tools (such as Segger J-Link) with files
 built under the Linux VM is not a possibility.</p></li>
 <li><p>The Cygwin environment.  Instructions for installation of Cygwin on a
 Windows system are provided in the following paragraph, “Installing
 Cygwin”.  Cygwin is a mature, well-tested, and very convenient
 environment.  It is especially convenient if you  need to
 integrate with Windows tools and files.  Downsides are that the
 installation time is very long and the compile times are slow.</p></li>
 <li><p>Ubuntu/Bash shell under Windows 10.  This is a new option under
 Windows 10.  See the section “Ubuntu Bash under Windows 10” below.
 This is an improvement over Cygwin if your concern is compile time;
 its build performance is comparable to native Linux, certainly better
 than the Cygwin build time.  It also installs in a tiny fraction of
 the time as Cygwin, perhaps 20 minutes for the basic Ubuntu install
 (vs. more than a day for the complete Cygwin install).</p>
 <p>There have been even more recent ports of Linux environment to
 Windows.  I need to update this section to include some mention of
 these alternatives.</p>
 </li>
 <li><p>The MSYS environment.  MSYS derives from an older version of Cygwin
 simplified and adapted to work more naturally in the Windows
 environment.  See <a class="reference external" href="http://www.mingw.org/wiki/MSYS">http://www.mingw.org/wiki/MSYS</a> if you are
 interested in using MSYS.  The advantages of the MSYS environment is
 that it is better integrted with the native Windows environment and
 lighter weight; it uses only a  minimal number of add-on POSIX-land
 tools.</p>
 <p>The download link in that Wiki takes you to the SourceForge download
 site.  The SourceForge MSYS project has been stagnant for some time.
 The MSYS project has more recently moved to
 <a class="reference external" href="http://odsn.net/projects/sfnet_mingwbundle">http://odsn.net/projects/sfnet_mingwbundle</a>.  Downloads of current .zip
 files are available there but no instructions for the installation.</p>
 </li>
 <li><p>MSYS2 appears to be a re-write of MSYS based on a newer version of
 Cygwin.  Is it available at <a class="reference external" href="https://www.msys2.org">https://www.msys2.org</a>.  A windows
 installer is available at that site along with very good installation
 instructions.  The download is relatively quick (at least compared to
 Cygwin) and the ‘pacman’ package management tool supports supports
 simple system updates.  For example, ‘pacman -S git’ will install the
 GIT command line utilities.</p></li>
 <li><p>Other POSIX environments.  Check out:</p>
 <ul class="simple">
 <li><p>UnxUtils: <a class="reference external" href="https://sourceforge.net/projects/unxutils/">https://sourceforge.net/projects/unxutils/</a>,
 <a class="reference external" href="https://en.wikipedia.org/wiki/UnxUtils">https://en.wikipedia.org/wiki/UnxUtils</a></p></li>
 <li><p>MobaXterm: <a class="reference external" href="https://mobaxterm.mobatek.net/">https://mobaxterm.mobatek.net/</a></p></li>
 <li><p>Gow: <a class="reference external" href="https://github.com/bmatzelle/gow/wiki">https://github.com/bmatzelle/gow/wiki</a></p></li>
 </ul>
 <p><strong>Disclaimer</strong>:  In principle, these should work.  However, I have never
 used any of these environments and cannot guarantee that there is
 not some less-than-obvious issues.</p>
 </li>
 </ul>
 <p>NuttX can also be installed and built on a native Windows system, but with
 some potential tool-related issues (see the discussion “Native Windows
 Build” under “Building NuttX” below).  GNUWin32 is used to provide
 compatible native windows tools.</p>
 <section id="installing-cygwin">
 <h3>Installing Cygwin<a class="headerlink" href="#installing-cygwin" title="Permalink to this heading"></a></h3>
 <p>Installing Cygwin on your Windows PC is simple, but time consuming.  See
 <a class="reference external" href="http://www.cygwin.com/">http://www.cygwin.com/</a> for installation instructions. Basically you just
 need to download a tiny setup.exe program and it does the real, network
 installation for you.</p>
 <p>Some Cygwin installation tips:</p>
 <ol class="arabic simple">
 <li><p>Install at <code class="docutils literal notranslate"><span class="pre">C:\cygwin</span></code></p></li>
 <li><p>Install <strong>everything</strong>:  “Only the minimal base packages from the
 Cygwin distribution are installed by default. Clicking on categories
 and packages in the setup.exe package installation screen will
 provide you with the ability to control what is installed or updated.
 Clicking on the “Default” field next to the “All” category will
 provide you with the opportunity to install every Cygwin package.
 Be advised that this will download and install hundreds of megabytes
 to your computer.”</p></li>
 </ol>
 <p>If you use the “default” installation, you will be missing many
 of the Cygwin utilities that you will need to build NuttX.  The
 build will fail in numerous places because of missing packages.</p>
 <p>NOTE: The last time I installed <strong>everything</strong>, the download was
 about 5GiB.  The server I selected was also very slow so it took
 over a day to do the whole install!</p>
 <p>NOTE: You don’t really have to install <strong>everything</strong> but I cannot
 answer the question “Then what should I install?”  I don’t know
 the answer to that and so will continue to recommend installing
 <strong>everything</strong>.</p>
 <p>You should certainly be able to omit “Science”, “Math”, and
 “Publishing”.  You can try omitting KDE, Gnome, GTK, and other
 graphics packages if you don’t plan to use them.</p>
 <p>Perhaps a minimum set would be those packages listed below for the
 “Ubuntu Bash under Windows 10” installation?</p>
 <p><strong>UPDATE</strong>:  Sergey Frolov had success with the following minimal
 Cygwin configuration:</p>
 <ol class="arabic">
 <li><p>After starting the Cygwin installer, keep the recommended
 packages that are pre-selected in the default configuration.</p></li>
 <li><p>Using the installation tools, add the following packages:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>make (GNU make)  bison        libgmp3-dev
 gcc-core         byacc        libmpfr-dev
 gcc-g++          gperf        libmpc-dev
 flex             gdb          automake-1.15
 libncurses-dev   libgmp-dev   curl
 </pre></div>
 </div>
 </li>
 </ol>
 <p>After installing Cygwin, you will get lots of links for installed
 tools and shells.  I use the RXVT native shell.  It is fast and reliable
 and does not require you to run the Cygwin X server (which is neither
 fast nor reliable).  Unless otherwise noted, the rest of these
 instructions assume that you are at a bash command line prompt in
 either Linux or in Cygwin shell.</p>
 </section>
 <section id="using-msys">
 <h3>Using MSYS<a class="headerlink" href="#using-msys" title="Permalink to this heading"></a></h3>
 <p>MSYS is an environment the derives from Cygwin.  Thus, most things said
 about Cygwin apply equally to MSYS.  This section will, then, focus on
 the differences when using MSYS, specifically MSYS2.</p>
 <p>Here is it assumed that you have already downloaded and installed MSYS2
 from <a class="reference external" href="https://www.msys2.org">https://www.msys2.org</a> using the windows installer available at that
 location.  It is also assumed that you have brought in the necessary
 tools using the ‘pacman’ package management tool Tools needed including:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>pacman -S git
 pacman -S make
 pacman -S gcc
 pacman -S gdb
 </pre></div>
 </div>
 <p>And possibly others depending upon your usage.  Then you will need to
 build and install kconfig-frontends per the instructions of the top-level
 README.txt file in the tools repository.  This requires the following
 additional tools:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>pacman -S bison
 pacman -S curl
 pacman -S gperf
 pacman -S ncurses-devel
 pacman -S automake-wrapper
 pacman -S autoconf
 pacman -S pkg-config
 </pre></div>
 </div>
 <p>Because of some versioning issues, I had to run ‘aclocal’ prior to
 running the kconfig-frontends configure script.  See “Configuring NuttX”
 below for further information.</p>
 <p>Unlike Cygwin, MSYS does not support symbolic links.  The ‘ln -s’ command
 will, in fact, copy a directory!  This means that you Make.defs file will
 have to include definitions like:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>ifeq ($(CONFIG_WINDOWS_MSYS),y)
   DIRLINK = $(TOPDIR)/tools/copydir.sh
   DIRUNLINK = $(TOPDIR)/tools/unlink.sh
 endif
 </pre></div>
 </div>
 <p>This will force the directory copies to work in a way that can be handled
 by the NuttX build system.  NOTE:  The default link.sh script has been
 updated so that is should now be MSYS2 compatible.  The above is preferred
 but no longer necessary in the Make.defs file.</p>
 <p>To build the simulator under MSYS, you also need:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>pacman -S zlib-devel
 </pre></div>
 </div>
 <p>It appears that you cannot use directory names with spaces in them like
 “/c/ProgramFiles (86)” in the MSYS path variable.  I worked around this
 by create Windows junctions like this:</p>
 <ol class="arabic">
 <li><p>Open the a windows command terminal,</p></li>
 <li><p>cd to <code class="docutils literal notranslate"><span class="pre">c:\msys64</span></code>, then</p></li>
 <li><p><code class="docutils literal notranslate"><span class="pre">mklink</span> <span class="pre">/j</span> <span class="pre">programfiles</span> <span class="pre">&quot;C:/Program\</span> <span class="pre">Files&quot;</span></code> and</p></li>
 <li><p><code class="docutils literal notranslate"><span class="pre">mklink</span> <span class="pre">/j</span> <span class="pre">programfiles86</span> <span class="pre">&quot;C:/Program\</span> <span class="pre">Files\</span> <span class="pre">\(x86\)&quot;</span></code></p>
 <p>They then show up as <code class="docutils literal notranslate"><span class="pre">/programfiles</span></code> and <code class="docutils literal notranslate"><span class="pre">/programfiles86</span></code> with the MSYS2
 sandbox.  Those paths can then be used with the PATH variable.  I had
 to do something similar for the path to the GNU Tools “ARM Embedded
 Toolchain” which also has spaces in the path name.</p>
 </li>
 </ol>
 </section>
 <section id="ubuntu-bash-under-windows-10">
 <h3>Ubuntu Bash under Windows 10<a class="headerlink" href="#ubuntu-bash-under-windows-10" title="Permalink to this heading"></a></h3>
 <p>A better version of a command-line only Ubuntu under Windows 10 (beta)
 has recently been made available from Microsoft.</p>
 <section id="installation-for-ubuntu-bash-under-windows-10">
 <h4>Installation for Ubuntu Bash under Windows 10<a class="headerlink" href="#installation-for-ubuntu-bash-under-windows-10" title="Permalink to this heading"></a></h4>
 <p>Installation instructions abound on the Internet complete with screen
 shots.  I will attempt to duplicate those instructions in full here.
 Here are the simplified installation steps:</p>
 <ul>
 <li><p>Open <em>Settings</em>.</p></li>
 <li><p>Click on <em>Update &amp; security</em>.</p></li>
 <li><p>Click on <em>For Developers</em>.</p></li>
 <li><p>Under <em>Use developer features</em>, select the <em>Developer mode</em> option to
 setup the environment to install Bash.</p></li>
 <li><p>A message box should pop up.  Click <em>Yes</em> to turn on developer mode.</p></li>
 <li><p>After the necessary components install, you’ll need to restart your
 computer.</p>
 <p>Once your computer reboots:</p>
 </li>
 <li><p>Open <em>Control Panel</em>.</p></li>
 <li><p>Click on <em>Programs</em>.</p></li>
 <li><p>Click on <em>Turn Windows features on or off</em>.</p></li>
 <li><p>A list of features will pop up, check the <em>Windows Subsystem for Linux
 (beta)</em> option.</p></li>
 <li><p>Click <em>OK</em>.</p></li>
 <li><p>Once the components installed on your computer, click the <em>Restart
 now</em> button to complete the task.</p>
 <p>After your computer restarts, you will notice that Bash will not appear in
 the <em>Recently added</em> list of apps, this is because Bash isn’t actually
 installed yet. Now that you have setup the necessary components, use the
 following steps to complete the installation of Bash:</p>
 </li>
 <li><p>Open <em>Start</em>, do a search for <code class="docutils literal notranslate"><span class="pre">bash.exe</span></code>, and press <em>Enter</em>.</p></li>
 <li><p>On the command prompt, type <code class="docutils literal notranslate"><span class="pre">y</span></code> and press Enter to download and install
 Bash from the Windows Store.  This will take awhile.</p></li>
 <li><p>Then you’ll need to create a default UNIX user account. This account
 doesn’t have to be the same as your Windows account. Enter the
 username in the required field and press Enter (you can’t use the
 username <code class="docutils literal notranslate"><span class="pre">admin</span></code>).</p></li>
 <li><p>Close the <code class="docutils literal notranslate"><span class="pre">bash.exe</span></code> command prompt.</p>
 <p>Now that you completed the installation and setup, you can open the Bash
 tool from the Start menu like you would with any other app.</p>
 </li>
 </ul>
 </section>
 <section id="accessing-windows-files-from-ubuntu">
 <h4>Accessing Windows Files from Ubuntu<a class="headerlink" href="#accessing-windows-files-from-ubuntu" title="Permalink to this heading"></a></h4>
 <p>File systems will be mounted under <code class="docutils literal notranslate"><span class="pre">/mnt</span></code> so for example <code class="docutils literal notranslate"><span class="pre">C:\Program</span> <span class="pre">Files</span></code>
 appears at <code class="docutils literal notranslate"><span class="pre">/mnt/c/Program</span> <span class="pre">Files</span></code>.  This is as opposed to Cygwin where
 the same directory would appear at <code class="docutils literal notranslate"><span class="pre">/cygdrive/c/Program</span> <span class="pre">Files</span></code>.</p>
 <p>With these differences (perhaps a few other Windows quirks) the Ubuntu
 install works just like Ubuntu running natively on your PC.</p>
 <p>A good tip for file sharing is to use symbolic links within your Ubuntu
 home directory.  For example, suppose you have your <code class="docutils literal notranslate"><span class="pre">projects</span></code> directory
 at <code class="docutils literal notranslate"><span class="pre">C:\Documents\projects</span></code>.  Then you can set up a link to the <code class="docutils literal notranslate"><span class="pre">projects/</span></code>
 directory in your Ubuntu directory like:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>ln -s /mnt/c/Documents/projects projects
 </pre></div>
 </div>
 </section>
 <section id="accessing-ubuntu-files-from-windows">
 <h4>Accessing Ubuntu Files From Windows<a class="headerlink" href="#accessing-ubuntu-files-from-windows" title="Permalink to this heading"></a></h4>
 <p>In Ubuntu Userspace for Windows, the Ubuntu file system root directory is
 at:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>%localappdata%\lxss\rootfs
 </pre></div>
 </div>
 <p>Or</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>C:\Users\Username\AppData\Local\lxss\rootfs
 </pre></div>
 </div>
 <p>However, I am unable to see my files under the rootfshome directory.
 After some looking around, I find the home directory
 <code class="docutils literal notranslate"><span class="pre">%localappdata%\lxss\home</span></code>.</p>
 <p>With that trick access to the <code class="docutils literal notranslate"><span class="pre">/home</span></code> directory, you should actually be
 able to use Windows tools outside of the Ubuntu sandbox with versions of
 NuttX built within the sandbox using that path.</p>
 </section>
 <section id="executing-windows-tools-from-ubuntu">
 <h4>Executing Windows Tools from Ubuntu<a class="headerlink" href="#executing-windows-tools-from-ubuntu" title="Permalink to this heading"></a></h4>
 <p>You can also execute Windows tools from within the Ubuntu sandbox:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>/mnt/c/Program\ Files\ \(x86\)/Microchip/xc32/v1.43/bin/xc32-gcc.exe --version
 Unable to translate current working directory. Using C:\WINDOWS\System32
 xc32-gcc.exe (Microchip Technology) 4.8.3 MPLAB XC32 Compiler v1.43 Build date: Mar  1 2017
 ...
 </pre></div>
 </div>
 <p>The error message indicates that there are more issues:  You cannot mix
 Windows tools that use Windows style paths in an environment that uses
 POSIX paths.  I think you would have to use Linux tools only from within
 the Ubuntu sandbox.</p>
 </section>
 <section id="install-ubuntu-software">
 <h4>Install Ubuntu Software<a class="headerlink" href="#install-ubuntu-software" title="Permalink to this heading"></a></h4>
 <p>Use <code class="docutils literal notranslate"><span class="pre">sudo</span> <span class="pre">apt-get</span> <span class="pre">install</span> <span class="pre">&lt;package</span> <span class="pre">name&gt;</span></code>.  As examples, this is how
 you would get GIT:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>sudo apt-get install git
 </pre></div>
 </div>
 <p>This will get you a compiler for your host PC:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>sudo apt-get install gcc
 </pre></div>
 </div>
 <p>This will get you an ARM compiler for your target:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>sudo apt-get install gcc-arm-none-eabi
 </pre></div>
 </div>
 <p><strong>NOTE</strong>: That is just an example.  I am not sure if apt-get will give you a
 current or usable compiler.  You should carefully select your toolchain
 for the needs of your project.</p>
 <p>You will also need to get the kconfig-frontends configuration as
 described below under <em>NuttX Configuration Tool</em>.  In order to build the
 kconfig-frontends configuration tool you will also need: <code class="docutils literal notranslate"><span class="pre">make</span></code>, <code class="docutils literal notranslate"><span class="pre">gperf</span></code>,
 <code class="docutils literal notranslate"><span class="pre">flex</span></code>, <code class="docutils literal notranslate"><span class="pre">bison</span></code>, and <code class="docutils literal notranslate"><span class="pre">libncurses-dev</span></code>.</p>
 <p>That is enough to do a basic NuttX build.</p>
 </section>
 <section id="integrating-with-windows-tools">
 <h4>Integrating with Windows Tools<a class="headerlink" href="#integrating-with-windows-tools" title="Permalink to this heading"></a></h4>
 <p>If you want to integrate with Windows native tools, then you would need
 deal with the same kind of craziness as with integrating Cygwin with
 native toolchains, see the section <em>Cygwin Build Problems</em> below.</p>
 <p>However, there is currently no build support for using Windows native
 tools with Ubuntu under Windows.  This tool combination is made to work
 with Cygwin through the use of the <code class="docutils literal notranslate"><span class="pre">cygpath</span> <span class="pre">-w</span></code> tool that converts paths
 from say <code class="docutils literal notranslate"><span class="pre">/cydrive/c/Program</span> <span class="pre">Files</span></code> to <code class="docutils literal notranslate"><span class="pre">C:\Program</span> <span class="pre">Files</span></code>.  There is,
 however, no corresponding tool to convert <code class="docutils literal notranslate"><span class="pre">/mnt/c/Program</span> <span class="pre">Files</span></code> in the
 Ubuntu environment.</p>
 </section>
 <section id="graphics-support">
 <h4>Graphics Support<a class="headerlink" href="#graphics-support" title="Permalink to this heading"></a></h4>
 <p>The Ubuntu version support by Microsoft is a command-line only version.
 There is no support for Linux graphics utilities.</p>
 <p>This limitation is not a limitation of Ubuntu, however, only in what
 Microsoft is willing to support.  If you install a X-Server, then you
 can also use basic graphics utilities.  See for example:</p>
 <blockquote>
 <div><p><a class="reference external" href="http://www.howtogeek.com/261575/how-to-run-graphical-linux-desktop-applications-from-windows-10s-bash-shell/">http://www.howtogeek.com/261575/how-to-run-graphical-linux-desktop-applications-from-windows-10s-bash-shell/</a></p>
 </div></blockquote>
 <p>Many Linux graphics programs would, however, also require a graphics
 framework like GTK or Qt.  So this might be a trip down the rabbit hole.</p>
 </section>
 <section id="using-macos">
 <h4>Using macOS<a class="headerlink" href="#using-macos" title="Permalink to this heading"></a></h4>
 <p>You need to install at least the following tools specific to macOS.</p>
 <ul class="simple">
 <li><p>flock (used by APPDIR build logic)</p></li>
 </ul>
 <p>A macOS port is available at: <a class="reference external" href="https://github.com/discoteq/flock">https://github.com/discoteq/flock</a></p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span> brew tap discoteq/discoteq
  brew install flock


 If you want to build the sim:
 </pre></div>
 </div>
 <ul>
 <li><p>Xcode (the native compiler and the rest of the toolchain)</p></li>
 <li><p>ELF toolchain (if you want to build modules for CONFIG_LIBC_MODLIB)</p>
 <p>brew install x86_64-elf-gcc</p>
 </li>
 </ul>
 </section>
 </section>
 </section>
 <section id="installation">
 <h2>INSTALLATION<a class="headerlink" href="#installation" title="Permalink to this heading"></a></h2>
 <p>There are two ways to get NuttX:  You may download released, stable
 tarballs from either the project website.  Or you may get NuttX by
 cloning the GIT repositories.  Let’s consider the released tarballs
 first:</p>
 <section id="download-and-unpack">
 <h3>Download and Unpack<a class="headerlink" href="#download-and-unpack" title="Permalink to this heading"></a></h3>
 <p>Download and unpack the NuttX tarball.  If you are reading this, then
 you have probably already done that.  After unpacking, you will end
 up with a directory called nuttx-version (where version is the NuttX
 version number). You might want to rename that directory nuttx to
 match the various instructions in the documentation and some scripts
 in the source tree.</p>
 <ul>
 <li><p>Download location:</p>
 <p><a class="reference external" href="https://nuttx.apache.org/download/">https://nuttx.apache.org/download/</a></p>
 </li>
 <li><p>Legacy download locations:</p>
 <p><a class="reference external" href="https://bitbucket.org/nuttx/nuttx/downloads">https://bitbucket.org/nuttx/nuttx/downloads</a>
 <a class="reference external" href="https://sourceforge.net/projects/nuttx/files/nuttx/">https://sourceforge.net/projects/nuttx/files/nuttx/</a></p>
 </li>
 </ul>
 </section>
 <section id="semi-optional-apps-package">
 <h3>Semi-Optional apps/ Package<a class="headerlink" href="#semi-optional-apps-package" title="Permalink to this heading"></a></h3>
 <p>All NuttX libraries and example code used to be in included within
 the NuttX source tree.  As of NuttX-6.0, this application code was
 moved into a separate tarball, the apps tarball.  If you are just
 beginning with NuttX, then you will want to download the versioned
 apps tarball along with the NuttX tarball.  If you already have your
 own product application directory, then you may not need the apps
 tarball.</p>
 <p>It is called “Semi-optional” because if you don’t have some <code class="docutils literal notranslate"><span class="pre">apps/</span></code>
 directory, NuttX will <em>fail</em> to build! You do not necessarily need
 to use the NuttX apps tarball but may, instead, provide your own
 custom application directory.  Such a custom directory would need
 to include a valid Makefile to support the build and a valid Kconfig
 file to support the configuration.  More about these files later.</p>
 <p>Download then unpack the apps tarball in the same directory where you
 unpacked the NuttX tarball.  After you unpack the apps tarball, you
 will have a new directory called apps-version (where the version
 should exactly match the version of the NuttX tarball).  Again, you
 might want to rename the directory to simply apps/ to match what
 you read in the documentation</p>
 <p>After unpacking (and renaming) the apps tarball, you will have two
 directories side by side like this:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>       |
   +----+----+
   |         |
 nuttx/     apps/
 </pre></div>
 </div>
 <p>This is important because the NuttX build will expect to find the
 apps directory in that (default) location.  That default location
 can be changed by modifying your NuttX configuration file, but that
 is another story.</p>
 </section>
 <section id="installation-directories-with-spaces-in-the-path">
 <h3>Installation Directories with Spaces in the Path<a class="headerlink" href="#installation-directories-with-spaces-in-the-path" title="Permalink to this heading"></a></h3>
 <p>The nuttx build directory should reside in a path that contains no
 spaces in any higher level directory name.  For example, under
 Cygwin, your home directory might be formed from your first and last
 names like: <code class="docutils literal notranslate"><span class="pre">/home/First</span> <span class="pre">Last</span></code>. That will cause strange errors when
 the make system tries to build.</p>
 <dl class="simple">
 <dt>[Actually, that problem is probably not too difficult to fix.  Some</dt><dd><p>Makefiles probably just need some paths within double quotes]</p>
 </dd>
 </dl>
 <p>I work around spaces in the home directory name, by creating a
 new directory that does not contain any spaces, such as <code class="docutils literal notranslate"><span class="pre">/home/nuttx</span></code>.
 Then I install NuttX in <code class="docutils literal notranslate"><span class="pre">/home/nuttx</span></code> and always build from
 <code class="docutils literal notranslate"><span class="pre">/home/nuttx/nuttx-code</span></code>.</p>
 </section>
 <section id="downloading-from-repositories">
 <h3>Downloading from Repositories<a class="headerlink" href="#downloading-from-repositories" title="Permalink to this heading"></a></h3>
 <section id="cloning-the-repository">
 <h4>Cloning the Repository<a class="headerlink" href="#cloning-the-repository" title="Permalink to this heading"></a></h4>
 <p><strong>BEFORE</strong> cloning repositories on any Windows platform do the following GIT
 command:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>git config --global core.autocrlf false
 </pre></div>
 </div>
 <p>That will avoid conversions of linefeeds (newlines, n) to carriage
 return plus linefeed sequences (rn)</p>
 <p>The current NuttX du jour is available in from a GIT repository.  Here are
 instructions for cloning the core NuttX RTOS (corresponding to the nuttx
 tarball discussed above):</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>git clone https://gitbox.apache.org/repos/asf/nuttx.git nuttx
 </pre></div>
 </div>
 <p>-or-</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>git clone https://github.com/apache/nuttx.git nuttx
 </pre></div>
 </div>
 <p>And the semi-optional apps/ application directory and be cloned like:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>git clone https://gitbox.apache.org/repos/asf/nuttx-apps.git apps
 </pre></div>
 </div>
 <p>-or-</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>git clone https://github.com/apache/nuttx-apps.git apps
 </pre></div>
 </div>
 <p>That will give you the same directory structure like this:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>       |
   +----+----+
   |         |
 nuttx/     apps/
 </pre></div>
 </div>
 </section>
 <section id="configuring-the-clones">
 <h4>Configuring the Clones<a class="headerlink" href="#configuring-the-clones" title="Permalink to this heading"></a></h4>
 <p>The following steps need to be performed for each of the repositories.
 After changing to the clone directory:</p>
 <p>Set your identity:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>git config --global user.name &quot;My Name&quot;
 git config --global user.email my.name@example.com
 </pre></div>
 </div>
 <p>Colorized diffs are much easier to read:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>git config --global color.branch auto
 git config --global color.diff auto
 git config --global color.interactive auto
 git config --global color.status auto
 </pre></div>
 </div>
 <p>Checkout other settings</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>git config --list
 </pre></div>
 </div>
 </section>
 <section id="cloning-nuttx-inside-cygwin">
 <h4>Cloning NuttX Inside Cygwin<a class="headerlink" href="#cloning-nuttx-inside-cygwin" title="Permalink to this heading"></a></h4>
 <p>If you are cloning the NuttX repository, it is recommended to avoid
 automatic end of lines conversions by git. These conversions may break
 some scripts like configure.sh. Before cloning, do the following:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>git config --global core.autocrlf false
 </pre></div>
 </div>
 </section>
 </section>
 <section id="related-repositories">
 <h3>Related Repositories<a class="headerlink" href="#related-repositories" title="Permalink to this heading"></a></h3>
 <p>These are standalone repositories:</p>
 <ul>
 <li><p><a class="reference external" href="https://gitbox.apache.org/repos/asf/nuttx-apps">https://gitbox.apache.org/repos/asf/nuttx-apps</a>
 or
 <a class="reference external" href="https://github.com/apache/nuttx-apps.git">https://github.com/apache/nuttx-apps.git</a></p>
 <p>This directory holds an optional package of applications and libraries
 can be used with the NuttX RTOS.  There is a README.txt file there that
 will provide more information about that package.</p>
 </li>
 <li><p><a class="reference external" href="https://bitbucket.org/nuttx/nxwidgets">https://bitbucket.org/nuttx/nxwidgets</a></p>
 <p>This is the NuttX C++ graphics support.  This includes NxWM, the tiny
 NuttX Window Manager.</p>
 </li>
 <li><p><a class="reference external" href="https://bitbucket.org/nuttx/uclibc">https://bitbucket.org/nuttx/uclibc</a></p>
 <p>This repository contains a version of the uClibc++ C++ library.  This code
 originates from <a class="reference external" href="http://cxx.uclibc.org/">http://cxx.uclibc.org/</a> and has been adapted for NuttX by the
 RGMP team (<a class="reference external" href="http://rgmp.sourceforge.net/wiki/index.php/Main_Page">http://rgmp.sourceforge.net/wiki/index.php/Main_Page</a>).</p>
 </li>
 <li><p><a class="reference external" href="https://bitbucket.org/nuttx/buildroot">https://bitbucket.org/nuttx/buildroot</a></p>
 <p>A environment that you can to use to build a custom, NuttX GNU toolchain.</p>
 </li>
 <li><p><a class="reference external" href="https://bitbucket.org/nuttx/tools">https://bitbucket.org/nuttx/tools</a></p>
 <p>There are snapshots of some tools here that you will need to work with
 NuttX:  kconfig-frontends, genromfs, and others.</p>
 </li>
 </ul>
 </section>
 <section id="notes-about-header-files">
 <h3>Notes about Header Files<a class="headerlink" href="#notes-about-header-files" title="Permalink to this heading"></a></h3>
 <section id="other-c-library-header-files">
 <h4>Other C-Library Header Files<a class="headerlink" href="#other-c-library-header-files" title="Permalink to this heading"></a></h4>
 <p>When a GCC toolchain is built, it must be built against a C library.
 The compiler together with the contents of the C library completes the
 C language definition and provides the complete C development
 environment.  NuttX provides its own, built-in C library.  So the
 complete, consistent C language definition for use with NuttX comes from
 the combination of the compiler and the header files provided by the
 NuttX C library.</p>
 <p>When a GCC toolchain is built, it incorporates the C library header
 files into the compiler internal directories and, in this way, the C
 library really becomes a part of the toolchain.  If you use the NuttX
 buildroot toolchain as described below under “NuttX Buildroot
 Toolchain”, your GCC toolchain will build against the NuttX C library
 and will incorporate the NuttX C library header files as part of the
 toolchain.</p>
 <p>If you use some other, third-party tool chain, this will not be the
 case, however.  Those toolchains were probably built against some
 other, incompatible C library distribution (such as newlib).  Those
 tools will have incorporated the incompatible C library header files
 as part of the toolchain.  These incompatible header files must <em>not</em>
 be used with NuttX because they will conflict with definitions in the
 NuttX built-in C-Library.  For such toolchains that include header
 files from a foreign C-Library, NuttX must be compiled without using
 the standard header files that are distributed with your toolchain.
 This prevents including conflicting, incompatible header files such
 as stdio.h.</p>
 <p>The math.h and stdarg.h are probably the two most trouble some header
 files to deal with.  These troublesome header files are discussed in
 more detail below.</p>
 </section>
 <section id="header-files-provided-by-your-toolchain">
 <h4>Header Files Provided by Your Toolchain<a class="headerlink" href="#header-files-provided-by-your-toolchain" title="Permalink to this heading"></a></h4>
 <p>Certain header files, such as <code class="docutils literal notranslate"><span class="pre">setjmp.h</span></code>, <code class="docutils literal notranslate"><span class="pre">stdarg.h</span></code>, and <code class="docutils literal notranslate"><span class="pre">math.h</span></code>, may still
 be needed from your toolchain and your compiler may not, however, be able
 to find these if you compile NuttX without using standard header files
 (i.e., with <code class="docutils literal notranslate"><span class="pre">-nostdinc</span></code>).  If that is the case, one solution is to copy
 those header file from your toolchain into the NuttX include directory.</p>
 </section>
 <section id="duplicated-header-files">
 <h4>Duplicated Header Files<a class="headerlink" href="#duplicated-header-files" title="Permalink to this heading"></a></h4>
 <p>There are also a few header files that can be found in the <code class="docutils literal notranslate"><span class="pre">nuttx/include</span></code>
 directory which are duplicated by the header files from your toolchain.
 stdint.h and stdbool.h are examples.  If you prefer to use the <code class="docutils literal notranslate"><span class="pre">stdint.h</span></code>
 and <code class="docutils literal notranslate"><span class="pre">stdbool.h</span></code> header files from your toolchain, those could be copied
 into the <code class="docutils literal notranslate"><span class="pre">nuttx/include/</span></code> directory. Using most other header files from
 your toolchain would probably cause errors.</p>
 </section>
 <section id="math-h">
 <h4>math.h<a class="headerlink" href="#math-h" title="Permalink to this heading"></a></h4>
 <p>Even though you should not use a foreign C-Library, you may still need
 to use other, external libraries with NuttX.  In particular, you may
 need to use the math library, libm.a.  NuttX supports a generic, built-in
 math library that can be enabled using <code class="docutils literal notranslate"><span class="pre">CONFIG_LIBM=y</span></code>.  However, you may
 still want to use a higher performance external math library that has
 been tuned for your CPU.  Sometimes such tuned math libraries are
 bundled with your toolchain.</p>
 <p>The math library header file, <code class="docutils literal notranslate"><span class="pre">math.h</span></code>, is a then special case.  If you do
 nothing, the standard math.h header file that is provided with your
 toolchain will be used.</p>
 <p>If you have a custom, architecture specific math.h header file, then
 that header file should be placed at <code class="docutils literal notranslate"><span class="pre">arch/&lt;cpu&gt;/include/math.h</span></code>.  There
 is a stub <code class="docutils literal notranslate"><span class="pre">math.h</span></code> header file located at <code class="docutils literal notranslate"><span class="pre">include/nuttx/lib/math.h</span></code>.  This stub
 header file can be used to “redirect” the inclusion to an architecture-
 specific math.h header file.  If you add an architecture specific math.h
 header file then you should also define <code class="docutils literal notranslate"><span class="pre">CONFIG_ARCH_MATH_H=y</span></code> in your
 NuttX Configuration file.  If <code class="docutils literal notranslate"><span class="pre">CONFIG_ARCH_MATH_H</span></code> is selected, then the
 top-level Makefile will copy the stub math.h header file from
 <code class="docutils literal notranslate"><span class="pre">include/nuttx/lib/math.h</span></code> to <code class="docutils literal notranslate"><span class="pre">include/math.h</span></code> where it will become the system
 <code class="docutils literal notranslate"><span class="pre">math.h</span></code> header file.  The stub <code class="docutils literal notranslate"><span class="pre">math.h</span></code> header file does nothing other
 than to include that architecture-specific <code class="docutils literal notranslate"><span class="pre">math.h</span></code> header file as the
 system <code class="docutils literal notranslate"><span class="pre">math.h</span></code> header file.</p>
 </section>
 <section id="float-h">
 <h4>float.h<a class="headerlink" href="#float-h" title="Permalink to this heading"></a></h4>
 <p>If you enable the generic, built-in math library, then that math library
 will expect your toolchain to provide the standard <code class="docutils literal notranslate"><span class="pre">float.h</span></code> header file.
 The float.h header file defines the properties of your floating point
 implementation.  It would always be best to use your toolchain’s <code class="docutils literal notranslate"><span class="pre">float.h</span></code>
 header file but if none is available, a default <code class="docutils literal notranslate"><span class="pre">float.h</span></code> header file will
 be provided if this option is selected.  However, there is no assurance
 that the settings in this <code class="docutils literal notranslate"><span class="pre">float.h</span></code> are actually correct for your platform!</p>
 </section>
 <section id="stdarg-h">
 <h4>stdarg.h<a class="headerlink" href="#stdarg-h" title="Permalink to this heading"></a></h4>
 <p>In most cases, the correct version of stdarg.h is the version provided
 with your toolchain.  However, sometimes there are issues with
 using your toolchains <code class="docutils literal notranslate"><span class="pre">stdarg.h</span></code>.  For example, it may attempt to draw in
 header files that do not exist in NuttX or perhaps the header files that
 it uses are not compatible with the NuttX header files.  In those cases,
 you can use an architecture-specific <code class="docutils literal notranslate"><span class="pre">stdarg.h</span></code> header file by defining
 <code class="docutils literal notranslate"><span class="pre">CONFIG_ARCH_STDARG_H=y</span></code>.</p>
 <p>See the discussion above for the <code class="docutils literal notranslate"><span class="pre">math.h</span></code> header.  This setting works
 exactly the same for the <code class="docutils literal notranslate"><span class="pre">stdarg.h</span></code> header file.</p>
 </section>
 </section>
 </section>
 <section id="configuring-nuttx">
 <h2>CONFIGURING NUTTX<a class="headerlink" href="#configuring-nuttx" title="Permalink to this heading"></a></h2>
 <section id="instantiating-canned-configurations">
 <h3>Instantiating “Canned” Configurations<a class="headerlink" href="#instantiating-canned-configurations" title="Permalink to this heading"></a></h3>
 <section id="configure-sh-and-configure-bat">
 <h4><code class="docutils literal notranslate"><span class="pre">configure.sh</span></code> and <code class="docutils literal notranslate"><span class="pre">configure.bat</span></code><a class="headerlink" href="#configure-sh-and-configure-bat" title="Permalink to this heading"></a></h4>
 <p>“Canned” NuttX configuration files are retained in:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>boards/&lt;arch-name&gt;/&lt;chip-name&gt;/&lt;board-name&gt;/configs/&lt;config-dir&gt;
 </pre></div>
 </div>
 <p>Where <code class="docutils literal notranslate"><span class="pre">&lt;board-name&gt;</span></code> is the name of your development board and <code class="docutils literal notranslate"><span class="pre">&lt;config-dir&gt;</span></code>
 is the name of the sub-directory containing a specific configuration for
 that board. <code class="docutils literal notranslate"><span class="pre">&lt;arch-name&gt;</span></code> and <code class="docutils literal notranslate"><span class="pre">&lt;chip-name&gt;</span></code> refer to characteristics of the
 MCU used on the board: <code class="docutils literal notranslate"><span class="pre">&lt;arch-name&gt;</span></code> is the CPU architecture implemented
 by the MCU; <code class="docutils literal notranslate"><span class="pre">&lt;chip-name&gt;</span></code> identifies the MCU chip family.  Only a few
 steps are required to instantiate a NuttX configuration, but to make the
 configuration even easier there are scripts available in the tools/
 sub-directory combines those simple steps into one command.</p>
 <p>There is one tool for use with any Bash-like shell that does configuration
 steps.  It is used as follows:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>tools/configure.sh &lt;board-name&gt;:&lt;config-dir&gt;
 </pre></div>
 </div>
 <p>There is an alternative Windows batch file that can be used in the windows
 native environment like:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>tools\configure.bat &lt;board-name&gt;:&lt;config-dir&gt;
 </pre></div>
 </div>
 <p>And, to make sure that other platforms are supported, there is also a
 C program at tools/configure.c that can be compiled to establish the
 board configuration.</p>
 <p>See <code class="docutils literal notranslate"><span class="pre">tools/README.txt</span></code> for more information about these scripts.</p>
 <p>General information about configuring NuttX can be found in:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>{TOPDIR}/boards/README.txt
 {TOPDIR}/boards/&lt;arch-name&gt;/&lt;chip-name&gt;/&lt;board-name&gt;/README.txt
 </pre></div>
 </div>
 </section>
 <section id="the-hidden-configuration-scripts">
 <h4>The Hidden Configuration Scripts:<a class="headerlink" href="#the-hidden-configuration-scripts" title="Permalink to this heading"></a></h4>
 <p>As mentioned above, there are only a few simple steps to instantiating a
 NuttX configuration.  Those steps are hidden by the configuration scripts
 but are summarized below:</p>
 <ol class="arabic">
 <li><p>Copy Files</p>
 <p>Configuring NuttX requires only copying two files from the
 <code class="docutils literal notranslate"><span class="pre">&lt;config-dir&gt;</span></code> to the directory where you installed NuttX (TOPDIR):</p>
 <ul>
 <li><p>Copy <code class="docutils literal notranslate"><span class="pre">boards/&lt;arch-name&gt;/&lt;chip-name&gt;/&lt;board-name&gt;/configs/&lt;config-dir&gt;/Make.def</span></code> to <code class="docutils literal notranslate"><span class="pre">{TOPDIR}/Make.defs</span></code></p>
 <p>OR</p>
 </li>
 <li><p>Copy <code class="docutils literal notranslate"><span class="pre">boards/&lt;arch-name&gt;/&lt;chip-name&gt;/&lt;board-name&gt;/scripts/Make.def</span></code>
 to <code class="docutils literal notranslate"><span class="pre">{TOPDIR}/Make.defs</span></code></p>
 <p>Make.defs describes the rules needed by your tool chain to compile
 and link code.  You may need to modify this file to match the
 specific needs of your toolchain.  NOTE that a configuration may
 have its own unique Make.defs file in its configuration directory or
 it may use a common Make.defs file for the board in the scripts/
 directory.  The first takes precedence.</p>
 </li>
 <li><p>Copy <code class="docutils literal notranslate"><span class="pre">boards/&lt;arch-name&gt;/&lt;chip-name&gt;/&lt;board-name&gt;/configs/&lt;config-dir&gt;/defconfig</span></code> to <code class="docutils literal notranslate"><span class="pre">{TOPDIR}/.config</span></code></p>
 <p>The defconfig file holds the actual build configuration.  This
 file is included by all other make files to determine what is
 included in the build and what is not.  This file is also used
 to generate a C configuration header at <code class="docutils literal notranslate"><span class="pre">include/nuttx/config.h</span></code>.</p>
 </li>
 <li><p>Copy other, environment-specific files to <code class="docutils literal notranslate"><span class="pre">{TOPDIR}</span></code></p>
 <p>This might include files like .gdbinit or IDE configuration files
 like .project or .cproject.</p>
 </li>
 </ul>
 </li>
 <li><p>Refresh the Configuration</p>
 <p>New configuration setting may be added or removed.  Existing settings
 may also change there values or options.  This must be handled by
 refreshing the configuration as described below.</p>
 <p>NOTE:  NuttX uses only compressed defconfig files.  For the NuttX
 defconfig files, this refreshing step is <em>NOT</em> optional; it is also
 necessary to uncompress and regenerate the full making file.  This is
 discussed further below.</p>
 </li>
 </ol>
 </section>
 </section>
 <section id="refreshing-configurations">
 <h3>Refreshing Configurations<a class="headerlink" href="#refreshing-configurations" title="Permalink to this heading"></a></h3>
 <p>Configurations can get out of date.  As new configuration settings are
 added or removed or as dependencies between configuration settings
 change, the contents of a default configuration can become out of synch
 with the build systems.  Hence, it is a good practice to “refresh” each
 configuration after configuring and before making.  To refresh the
 configuration, use the NuttX Configuration Tool like this:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>make oldconfig
 </pre></div>
 </div>
 <p>AFTER you have instantiated the NuttX configuration as described above.
 The configuration step copied the .config file into place in the top-level
 NuttX directory; ‘make oldconfig’ step will then operate on that .config
 file to bring it up-to-date.</p>
 <p>If your configuration is out of date, you will be prompted by ‘make oldconfig’
 to resolve the issues detected by the configuration tool, that is, to
 provide values for the new configuration options in the build system.  Doing
 this can save you a lot of problems down the road due to obsolete settings in
 the default board configuration file.  The NuttX configuration tool is
 discussed in more detail in the following paragraph.</p>
 <p>Confused about what the correct value for a new configuration item should
 be?  Enter ? in response to the ‘make oldconfig’ prompt and it will show
 you the help text that goes with the option.</p>
 <p>If you don’t want to make any decisions are willing to just accept the
 recommended default value for each new configuration item, an even easier
 way is:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>make olddefconfig
 </pre></div>
 </div>
 <p>The olddefconfig target will simply bring your configuration up to date with
 the current Kconfig files, setting any new options to the default value.
 No questions asked.</p>
 </section>
 <section id="nuttx-configuration-tool">
 <h3>NuttX Configuration Tool<a class="headerlink" href="#nuttx-configuration-tool" title="Permalink to this heading"></a></h3>
 <p>An automated tool has been incorporated to support re-configuration
 of NuttX.  This tool is based on the kconfig-frontends application available
 at <a class="reference external" href="https://bitbucket.org/nuttx/tools/src/master/kconfig-frontends/">https://bitbucket.org/nuttx/tools/src/master/kconfig-frontends/</a>.  (This
 is a snapshot of the old <a class="reference external" href="http://ymorin.is-a-geek.org/projects/kconfig-frontends">http://ymorin.is-a-geek.org/projects/kconfig-frontends</a>
 which is no longer available.)  This application provides a tool called
 <code class="docutils literal notranslate"><span class="pre">kconfig-mconf</span></code> that is used by the NuttX top-level Makefile. The following
 make target is provided:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>make menuconfig
 </pre></div>
 </div>
 <p>This make target will bring up NuttX configuration menus.</p>
 <p><strong>WARNING</strong>:  Never do <code class="docutils literal notranslate"><span class="pre">make</span> <span class="pre">menuconfig</span></code> on a configuration that has
 not been converted to use the kconfig-frontends tools!  This will
 damage your configuration (see
 <a class="reference external" href="https://cwiki.apache.org/confluence/display/NUTTX/Converting+Legacy+Configurations+to+Use+kconfig-mconf">https://cwiki.apache.org/confluence/display/NUTTX/Converting+Legacy+Configurations+to+Use+kconfig-mconf</a>).</p>
 <p>NuttX also supports kconfiglib(<a class="reference external" href="https://github.com/ulfalizer/Kconfiglib">https://github.com/ulfalizer/Kconfiglib</a>) by default,
 which is a Kconfig tool implemented in Python 2/3. Compared with kconfig-frontends,
 kconfiglib provides NuttX with the possibility of multi-platform support(configure
 NuttX in Winodws native/Visual Studio), and also kconfiglib has a stronger Kconfig
 syntax check, this will help developers to avoid some Kconfig syntax errors.
 Install kconfiglib via following command:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>pip install kconfiglib
 </pre></div>
 </div>
 <p>If you are a working on Windows, which also need the support of windows-curses:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>pip install windows-curses
 </pre></div>
 </div>
 <p><strong>NOTE</strong>:  It should be noted that kconfiglib does not support <strong>modules</strong> attributes.
 (<a class="reference external" href="https://github.com/ulfalizer/Kconfiglib/blob/master/kconfiglib.py#L3239-L3254">https://github.com/ulfalizer/Kconfiglib/blob/master/kconfiglib.py#L3239-L3254</a>,
 the community seems to have stopped updating), if the features depends on
 <code class="docutils literal notranslate"><span class="pre">CONFIG_BUILD_LOADABLE</span></code>, kconfiglib may not be a good choice.</p>
 <p>How do we tell a new configuration from an old one? See “Incompatibilities
 with Older Configurations” below.</p>
 <p>The <code class="docutils literal notranslate"><span class="pre">menuconfig</span></code> make target depends on two things:</p>
 <ol class="arabic">
 <li><p>The Kconfig configuration data files that appear in almost all
 NuttX directories.  These data files are the part that is still
 under development (patches are welcome!).  The Kconfig files
 contain configuration information for the configuration settings
 relevant to the directory in which the Kconfig file resides.</p>
 <p>NOTE: For a description of the syntax of this configuration file,
 see kconfig-language.txt in the tools repository at
 <a class="reference external" href="https://bitbucket.org/nuttx/tools">https://bitbucket.org/nuttx/tools</a></p>
 </li>
 <li><p>The <code class="docutils literal notranslate"><span class="pre">kconfig-mconf</span></code> tool. <code class="docutils literal notranslate"><span class="pre">kconfig-mconf</span></code> is part of the
 kconfig-frontends package.  You can download that package from the
 snapshot in the tools repository at <a class="reference external" href="https://bitbucket.org/nuttx/tools">https://bitbucket.org/nuttx/tools</a>.</p>
 <p>Building kconfig-frontends under Linux may be as simple as
 <code class="docutils literal notranslate"><span class="pre">configure;</span> <span class="pre">make;</span> <span class="pre">make</span> <span class="pre">install</span></code> but there may be some build
 complexities, especially if you are building under Cygwin.  See
 the more detailed build instructions in the top-level README.txt
 file of the tools repository at <a class="reference external" href="https://bitbucket.org/nuttx/tools">https://bitbucket.org/nuttx/tools</a>.</p>
 <p>The <code class="docutils literal notranslate"><span class="pre">make</span> <span class="pre">install</span></code> step will, by default, install the <code class="docutils literal notranslate"><span class="pre">kconfig-mconf</span></code>
 tool at <code class="docutils literal notranslate"><span class="pre">/usr/local/bin/mconf</span></code>.  Where ever you choose to
 install <code class="docutils literal notranslate"><span class="pre">kconfig-mconf</span></code>, make certain that your PATH variable includes
 a path to that installation directory.</p>
 <p>The kconfig-frontends tools will not build in a native Windows
 environment directly “out-of-the-box”.  For the Windows native
 case, you can use the modified version of kconfig-frontends
 that can be found at</p>
 <p><a class="reference external" href="http://uvc.de/posts/linux-kernel-configuration-tool-kconfig-under-windows.html">http://uvc.de/posts/linux-kernel-configuration-tool-kconfig-under-windows.html</a></p>
 <p>or a more recent port that can be found at</p>
 <p><a class="reference external" href="http://reclonelabs.com/more-kconfig-awesomeness-for-windows/">http://reclonelabs.com/more-kconfig-awesomeness-for-windows/</a>.</p>
 </li>
 </ol>
 <p>The basic configuration order is “bottom-up”:</p>
 <ul class="simple">
 <li><p>Select the build environment,</p></li>
 <li><p>Select the processor,</p></li>
 <li><p>Select the board,</p></li>
 <li><p>Select the supported peripherals</p></li>
 <li><p>Configure the device drivers,</p></li>
 <li><p>Configure the application options on top of this.</p></li>
 </ul>
 <p>This is pretty straight forward for creating new configurations
 but may be less intuitive for modifying existing configurations.</p>
 <p>Another ncurses-based tool that is an option to kconfig-mconf is
 kconfig-nconf.  The differences are primary in in the aesthetics of the
 UI.  If you have kconfig-nconf built, then you can invoke that front end
 with:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>make nconfig
 </pre></div>
 </div>
 <p>If you have an environment that supports the Qt or GTK graphical systems
 (probably KDE or gnome, respectively, or Cygwin under Windows with Qt or
 GTK installed), then you can also build the graphical kconfig-frontends,
 kconfig-qconf and kconfig-gconf.  In these case, you can start the
 graphical configurator with either:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>   make qconfig


 or
 </pre></div>
 </div>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>make gconfig
 </pre></div>
 </div>
 <p>Some keyboard shortcuts supported by kconfig-mconf, the tool that runs
 when you do ‘make menuconfig’:</p>
 <ul class="simple">
 <li><p><code class="docutils literal notranslate"><span class="pre">?</span></code> will bring up the mconfig help display.</p></li>
 <li><p><code class="docutils literal notranslate"><span class="pre">/</span></code> can be used find configuration selections.</p></li>
 <li><p><code class="docutils literal notranslate"><span class="pre">Z</span></code> can be used to reveal hidden configuration options</p></li>
 </ul>
 <p>These last two shortcuts are described further in the following
 paragraphs.</p>
 </section>
 <section id="finding-selections-in-the-configuration-menus">
 <h3>Finding Selections in the Configuration Menus<a class="headerlink" href="#finding-selections-in-the-configuration-menus" title="Permalink to this heading"></a></h3>
 <p>The NuttX configuration options have gotten complex and it can be very
 difficult to find options in the menu trees if you are not sure where
 to look.  The “basic configuration order” describe above can help to
 narrow things down.</p>
 <p>But if you know exactly what configuration setting you want to select,
 say <code class="docutils literal notranslate"><span class="pre">CONFIG_XYZ</span></code>, but not where to find it, then the <code class="docutils literal notranslate"><span class="pre">make</span> <span class="pre">menuconfig</span></code>
 version of the tool offers some help:  By pressing the ‘/’ key, the
 tool will bring up a menu that will allow you to search for a
 configuration item.  Just enter the string <code class="docutils literal notranslate"><span class="pre">CONFIG_XYZ</span></code> and press ENTER.
 It will show you not only where to find the configuration item, but
 also all of the dependencies related to the configuration item.</p>
 </section>
 <section id="reveal-hidden-configuration-options">
 <h3>Reveal Hidden Configuration Options<a class="headerlink" href="#reveal-hidden-configuration-options" title="Permalink to this heading"></a></h3>
 <p>If you type <code class="docutils literal notranslate"><span class="pre">Z</span></code>, then <code class="docutils literal notranslate"><span class="pre">kconfig-mconf</span></code> will change what is displayed.
 Normally, only enabled features that have all of their dependencies met
 are displayed.  That is, of course, not very useful if you would like to
 discover new options or if you are looking for an option and do not
 realize that the dependencies have not yet been selected and, hence, it
 is not displayed.</p>
 <p>But if you enter <code class="docutils literal notranslate"><span class="pre">Z</span></code>, then every option will be shown, whether or not its
 dependencies have been met.  You can then see everything that could be
 selected with the right dependency selections.  These additional options
 will be shown the <code class="docutils literal notranslate"><span class="pre">-</span></code> for the selection and for the value (since it
 cannot be selected and has no value).  About all you do is to select
 the <code class="docutils literal notranslate"><span class="pre">&lt;Help&gt;</span></code> option to see what the dependencies are.</p>
 </section>
 <section id="make-sure-that-you-are-on-the-right-platform">
 <h3>Make Sure that You are on the Right Platform<a class="headerlink" href="#make-sure-that-you-are-on-the-right-platform" title="Permalink to this heading"></a></h3>
 <p>Saved configurations may run on Linux, Cygwin (32- or 64-bit), or other
 platforms.  The platform characteristics can be changed use <code class="docutils literal notranslate"><span class="pre">make</span>
 <span class="pre">menuconfig</span></code>.  Sometimes this can be confusing due to the differences
 between the platforms.  Enter <code class="docutils literal notranslate"><span class="pre">sethost.sh</span></code></p>
 <p>sethost.sh is a simple script that changes a configuration to your
 host platform.  This can greatly simplify life if you use many different
 configurations.  For example, if you are running on Linux and you
 configure like this:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>tools/configure.sh board:configuration
 </pre></div>
 </div>
 <p>The you can use the following command to both (1) make sure that the
 configuration is up to date, AND (2) the configuration is set up
 correctly for Linux:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>tools/sethost.sh -l
 </pre></div>
 </div>
 <p>Or, if you are on a Windows/Cygwin 64-bit platform:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>tools/sethost.sh -c
 </pre></div>
 </div>
 <p>Or, for MSYS/MSYS2:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>tools/sethost.sh -g
 </pre></div>
 </div>
 <p>Other options are available from the help option built into the
 script.  You can see all options with:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>tools/sethost.sh -h
 </pre></div>
 </div>
 <p>Recently, the options to the configure.sh (and configure.bat) scripts have
 been extended so that you both setup the configuration, select for the host
 platform that you use, and uncompress and refresh the defconfig file all in
 one command like:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>tools/configure.sh -l board:configuration
 </pre></div>
 </div>
 <p>For a Linux host or for a Windows/Cygwin host:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>tools/configure.sh -c board:configuration
 </pre></div>
 </div>
 <p>Other options are available from the help option built into the
 script.  You can see all options with:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>tools/configure.sh -h
 </pre></div>
 </div>
 </section>
 <section id="comparing-two-configurations">
 <h3>Comparing Two Configurations<a class="headerlink" href="#comparing-two-configurations" title="Permalink to this heading"></a></h3>
 <p>If you try to compare two configurations using ‘diff’, you will probably
 not be happy with the result.  There are superfluous things added to
 the configuration files that make comparisons with the human eye
 difficult.</p>
 <p>There is a tool at nuttx/tools/cmpconfig.c that can be built to simplify
 these comparisons.  The output from this difference tool will show only
 the meaningful differences between two configuration files.  This tool is
 built as follows:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>cd nuttx/tools
 make -f Makefile.host
 </pre></div>
 </div>
 <p>This will create a program called ‘cmpconfig’ or ‘comconfig.exe’ on Windows.</p>
 <p>Why would you want to compare two configuration files?  Here are a few
 of the reasons why I do this</p>
 <ol class="arabic simple">
 <li><p>When I create a new configuration I usually base it on an older
 configuration and I want to know, “What are the options that I need to
 change to add the new feature to the older configurations?”  For example,
 suppose that I have a boardA/nsh configuration and I want to create a
 boardA/nxwm configuration.  Suppose I already have boardB/nsh and
 boardB/nxwm configurations.  Then by comparing the boardB/nsh with the
 boardB/nxwm I can see the modifications that I would need to make to my
 boardA/nsh to create a new  boardA/nxwm.</p></li>
 <li><p>But the most common reason that I use the ‘cmpconfig’ program is to
 check the results of “refreshing” a configuration with ‘make oldconfig’
 (see the paragraph “Refreshing Configurations” above).  The ‘make
 oldconfig’ command will make changes to my configuration and using
 ‘cmpconfig’, I can see precisely what those changes were and if any
 should be of concern to me.</p></li>
 <li><p>The ‘cmpconfig’ tool can also be useful when converting older, legacy
 manual configurations to the current configurations based on the
 kconfig-frontends tools.  See the following paragraph.</p></li>
 </ol>
 </section>
 <section id="making-defconfig-files">
 <h3>Making <code class="docutils literal notranslate"><span class="pre">defconfig</span></code> Files<a class="headerlink" href="#making-defconfig-files" title="Permalink to this heading"></a></h3>
 <section id="config-files-as-defconfig-files">
 <h4><code class="docutils literal notranslate"><span class="pre">.config</span></code> Files as <code class="docutils literal notranslate"><span class="pre">defconfig</span></code> Files:<a class="headerlink" href="#config-files-as-defconfig-files" title="Permalink to this heading"></a></h4>
 <p>The minimum <code class="docutils literal notranslate"><span class="pre">defconfig</span></code> file is simply the generated <code class="docutils literal notranslate"><span class="pre">.config</span></code> file with
 CONFIG_APPS_DIR setting removed or commented out.  That setting provides
 the name and location of the <code class="docutils literal notranslate"><span class="pre">apps/</span></code> directory relative to the <code class="docutils literal notranslate"><span class="pre">nuttx</span></code> build
 directory.  The default is <code class="docutils literal notranslate"><span class="pre">../apps/</span></code>, however, the apps directory may be
 any other location and may have a different name.  For example, the name
 of versioned NuttX releases are always in the form <code class="docutils literal notranslate"><span class="pre">apps-xx.yy</span></code> where <code class="docutils literal notranslate"><span class="pre">xx.yy</span></code>
 is the version number.</p>
 </section>
 <section id="finding-the-apps-directory-path">
 <h4>Finding the <code class="docutils literal notranslate"><span class="pre">apps/</span></code> Directory Path:<a class="headerlink" href="#finding-the-apps-directory-path" title="Permalink to this heading"></a></h4>
 <p>When the default configuration is installed using one of the scripts or
 programs in the NuttX tools directory, there will be an option to provide
 the path to the <code class="docutils literal notranslate"><span class="pre">apps/</span></code> directory.  If not provided, then the configure tool
 will look around and try to make a reasonable decision about where the
 <code class="docutils literal notranslate"><span class="pre">apps/</span></code> directory is located.</p>
 </section>
 <section id="compressed-defconfig-files">
 <h4>Compressed <code class="docutils literal notranslate"><span class="pre">defconfig</span></code> Files:<a class="headerlink" href="#compressed-defconfig-files" title="Permalink to this heading"></a></h4>
 <p>The <code class="docutils literal notranslate"><span class="pre">Makefile</span></code> also supports an option to generate very small <code class="docutils literal notranslate"><span class="pre">defconfig</span></code>
 files.  The <code class="docutils literal notranslate"><span class="pre">.config</span></code> files are quite large and complex.  But most of the
 settings in the <code class="docutils literal notranslate"><span class="pre">.config</span></code> file simply have the default settings from the
 <code class="docutils literal notranslate"><span class="pre">Kconfig</span></code> files.  These <code class="docutils literal notranslate"><span class="pre">.config</span></code> files can be converted into small <code class="docutils literal notranslate"><span class="pre">defconfig</span></code>
 file:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>make savedefconfig
 </pre></div>
 </div>
 <p>That make target will generate a defconfig file in the top-level
 directory.  The size reduction is really quite remarkable:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>wc -l .config defconfig
  1085 .config
    82 defconfig
  1167 total
 </pre></div>
 </div>
 <p>In order to be usable, the <code class="docutils literal notranslate"><span class="pre">.config</span></code> file installed from the compressed
 defconfig file must be reconstituted using:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>make olddefconfig
 </pre></div>
 </div>
 <blockquote>
 <div><p><strong>NOTE 1</strong>:  Only compressed defconfig files are retained in the NuttX repository.
 All patches and PRs that attempt to add or modify a defconfig file MUST
 use the compressed defconfig format as created by ‘make savdefconfig.’</p>
 <p><strong>NOTE 2</strong>:  When ‘make savedefconfig’ runs it will try several things some of
 which are expected to fail.  In these cases you will see an error message
 from make followed by “(ignored).”  You should also ignore these messages</p>
 </div></blockquote>
 <p><strong>CAUTION</strong>:  This size reduction was accomplished by removing all setting
 from the <code class="docutils literal notranslate"><span class="pre">.config</span></code> file that were at the default value. <code class="docutils literal notranslate"><span class="pre">make</span> <span class="pre">olddefconfig</span></code>
 can regenerate the original <code class="docutils literal notranslate"><span class="pre">.config</span></code> file by simply restoring those default
 settings.  The underlying assumption here is, of course, that the default
 settings do not change.  If the default settings change, and they often
 do, then the original <code class="docutils literal notranslate"><span class="pre">.config</span></code> may not be reproducible.</p>
 <p>So if your project requires 100% reproducibility over a long period of
 time, you make want to save the complete <code class="docutils literal notranslate"><span class="pre">.config</span></code> files vs. the standard,
 compressed <code class="docutils literal notranslate"><span class="pre">defconfig</span></code> file.</p>
 </section>
 <section id="configuring-with-compressed-defconfig-files">
 <h4>Configuring with “Compressed” defconfig Files:<a class="headerlink" href="#configuring-with-compressed-defconfig-files" title="Permalink to this heading"></a></h4>
 <p>As described above <code class="docutils literal notranslate"><span class="pre">defconfig</span></code>, all NuttX <code class="docutils literal notranslate"><span class="pre">defconfig</span></code> files are compressed
 using <code class="docutils literal notranslate"><span class="pre">make</span> <span class="pre">savedeconfig</span></code>.  These compressed <code class="docutils literal notranslate"><span class="pre">defconfig</span></code> files are
 generally not fully usable as they are and may not build the target
 binaries that you want because the compression process removed all of
 the default settings from the <code class="docutils literal notranslate"><span class="pre">defconfig</span></code> file.  To restore the default
 settings, you should run the following after configuring:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>make olddefconfig
 </pre></div>
 </div>
 <p>That will restore the the missing defaulted values.</p>
 <p>Using this command after configuring is generally a good practice anyway:
 Even if the <code class="docutils literal notranslate"><span class="pre">defconfig</span></code> files are not “compressed” in this fashion, the
 <code class="docutils literal notranslate"><span class="pre">defconfig</span></code> file may be old and the only way to assure that the installed
 <code class="docutils literal notranslate"><span class="pre">.config</span></code> is is up to date is via <code class="docutils literal notranslate"><span class="pre">make</span> <span class="pre">oldconfig</span></code> or <code class="docutils literal notranslate"><span class="pre">make</span> <span class="pre">olddefconfig</span></code>.
 See the paragraph above entitled “Refreshing Configurations” for
 additional information.</p>
 </section>
 </section>
 <section id="incompatibilities-with-older-configurations">
 <h3>Incompatibilities with Older Configurations<a class="headerlink" href="#incompatibilities-with-older-configurations" title="Permalink to this heading"></a></h3>
 <p><strong>WARNING</strong></p>
 <p>The current NuttX build system supports <em>only</em> the new compressed,
 <code class="docutils literal notranslate"><span class="pre">defconfig</span></code> configuration files generated using the <code class="docutils literal notranslate"><span class="pre">kconfig-frontends</span></code> tools
 as described in the preceding section.  Support for the older, legacy,
 manual configurations was eliminated in NuttX 7.0; support for
 uncompressed <code class="docutils literal notranslate"><span class="pre">.config-files-as-defconfig</span></code> files was eliminated after
 NuttX-7.21.  All configurations must now be done using the
 <code class="docutils literal notranslate"><span class="pre">kconfig-frontends</span></code> tool.  The older manual configurations and the new
 <code class="docutils literal notranslate"><span class="pre">kconfig-frontends</span></code> configurations are not compatible.  Old legacy
 configurations can <em>not</em> be used with the <code class="docutils literal notranslate"><span class="pre">kconfig-frontends</span></code> tool and,
 hence, cannot be used with releases of NuttX 7.0 and beyond:</p>
 <p>If you run <code class="docutils literal notranslate"><span class="pre">make</span> <span class="pre">menuconfig</span></code> with a legacy configuration the resulting
 configuration will probably not be functional.</p>
 <blockquote>
 <div><dl class="simple">
 <dt>Q: How can I tell if a configuration is a new kconfig-frontends</dt><dd><p>configuration or an older, manual configuration?</p>
 </dd>
 </dl>
 <p>A: Only old, manual configurations will have an appconfig file</p>
 <dl class="simple">
 <dt>Q: How can I convert a older, manual configuration into a new,</dt><dd><p>kconfig-frontends toolchain.</p>
 </dd>
 </dl>
 <p>A: Refer to <a class="reference external" href="https://cwiki.apache.org/confluence/display/NUTTX/Converting+Legacy+Configurations+to+Use+kconfig-mconf">https://cwiki.apache.org/confluence/display/NUTTX/Converting+Legacy+Configurations+to+Use+kconfig-mconf</a></p>
 </div></blockquote>
 <p><strong>WARNING</strong></p>
 <p>As described above, whenever you use a configuration, you really should
 always refresh the configuration with the following command <em>before</em> you
 make NuttX:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>make oldconfig
 </pre></div>
 </div>
 <p>OR</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>make olddefconfig
 </pre></div>
 </div>
 <p>This will make sure that the configuration is up-to-date in the event that
 it has lapsed behind the current NuttX development (see the paragraph
 “Refreshing Configurations” above).  But this only works with <em>new</em>
 configuration files created with the kconfig-frontends tools.</p>
 <p>Further, this step is <em>NOT</em> optional with the new, compressed defconfig
 files.  It is a necessary step that will also uncompress the defconfig
 file, regenerating the <code class="docutils literal notranslate"><span class="pre">.config</span></code> and making it usable for NuttX builds.</p>
 <p>Never do <code class="docutils literal notranslate"><span class="pre">make</span> <span class="pre">oldconfig</span></code> (OR <code class="docutils literal notranslate"><span class="pre">make</span> <span class="pre">menuconfig</span></code>) on a  configuration that
 has not been converted to use the kconfig-frontends tools!  This will
 damage your configuration (see
 <a class="reference external" href="https://cwiki.apache.org/confluence/display/NUTTX/Converting+Legacy+Configurations+to+Use+kconfig-mconf">https://cwiki.apache.org/confluence/display/NUTTX/Converting+Legacy+Configurations+to+Use+kconfig-mconf</a>).</p>
 </section>
 <section id="nuttx-configuration-tool-under-dos">
 <h3>NuttX Configuration Tool under DOS<a class="headerlink" href="#nuttx-configuration-tool-under-dos" title="Permalink to this heading"></a></h3>
 <blockquote>
 <div><p>Recent versions of NuttX support building NuttX from a native Windows
 console window (see <em>Native Windows Build</em> below).  But <code class="docutils literal notranslate"><span class="pre">kconfig-frontends</span></code>
 is a Linux tool.  At one time this was a problem for Windows users, but
 now there are two specially modified versions of the <code class="docutils literal notranslate"><span class="pre">kconfig-frontends</span></code>
 tools that can be used.  One can be found here:
 <a class="reference external" href="http://uvc.de/posts/linux-kernel-configuration-tool-kconfig-under-windows.html">http://uvc.de/posts/linux-kernel-configuration-tool-kconfig-under-windows.html</a></p>
 <p>The configuration steps of the most recent versions of NuttX require the
 <code class="docutils literal notranslate"><span class="pre">kconfig-tweak</span></code> tool that is not not available in the the above.  However,
 there has been an update to this <code class="docutils literal notranslate"><span class="pre">Kconfig</span></code> Windows tools that does include
 <cite>kconfig-tweak</cite>:  <a class="reference external" href="http://reclonelabs.com/more-kconfig-awesomeness-for-windows/">http://reclonelabs.com/more-kconfig-awesomeness-for-windows/</a></p>
 <p>Source code is available here: <a class="reference external" href="https://github.com/reclone/kconfig-frontends-win32">https://github.com/reclone/kconfig-frontends-win32</a>
 and <a class="reference external" href="https://github.com/reclone/kconfig-frontends-win32/releases">https://github.com/reclone/kconfig-frontends-win32/releases</a></p>
 <p>It is also possible to use the version of <code class="docutils literal notranslate"><span class="pre">kconfig-frontends</span></code> built
 under Cygwin outside of the Cygwin <em>sandbox</em> in a native Windows
 environment:</p>
 </div></blockquote>
 <ol class="arabic">
 <li><p>You can run the configuration tool using Cygwin.  However, the
 Cygwin <code class="docutils literal notranslate"><span class="pre">Win.mk</span></code> will complain so to do this will, you have
 to manually edit the <code class="docutils literal notranslate"><span class="pre">.config</span></code> file:</p>
 <ol class="loweralpha simple">
 <li><p>Delete the line: <code class="docutils literal notranslate"><span class="pre">CONFIG_WINDOWS_NATIVE=y</span></code></p></li>
 <li><p>Change the apps/ directory path, <code class="docutils literal notranslate"><span class="pre">CONFIG_APPS_DIR</span></code> to use Unix
 style delimiters.  For example, change <code class="docutils literal notranslate"><span class="pre">..\apps</span></code> to <code class="docutils literal notranslate"><span class="pre">../apps</span></code></p></li>
 </ol>
 <p>And of course, after you use the configuration tool you need to
 restore <code class="docutils literal notranslate"><span class="pre">CONFIG_WINDOWS_NATIVE=y</span></code> and the correct <code class="docutils literal notranslate"><span class="pre">CONFIG_APPS_DIR</span></code>.</p>
 </li>
 <li><p>You can, with some effort, run the Cygwin <code class="docutils literal notranslate"><span class="pre">kconfig-mconf</span></code> tool
 directly in the Windows console window.  In this case, you do not
 have to modify the <code class="docutils literal notranslate"><span class="pre">.config</span></code> file, but there are other complexities:</p>
 <ol class="loweralpha simple">
 <li><p>You need to temporarily set the Cygwin directories in the PATH
 variable then run <code class="docutils literal notranslate"><span class="pre">kconfig-mconf</span></code> manually like:</p></li>
 </ol>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span> kconfig-mconf Kconfig


 There is a Windows batch file at ``tools/kconfig.bat`` that automates
 these steps:
 </pre></div>
 </div>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>tools/kconfig menuconfig
 </pre></div>
 </div>
 <ol class="loweralpha simple" start="2">
 <li><p>There is an issue with accessing DOS environment variables from
 the Cygwin <code class="docutils literal notranslate"><span class="pre">kconfig-mconf</span></code> running in the Windows console.  The
 following change to the top-level <code class="docutils literal notranslate"><span class="pre">Kconfig</span></code> file seems to work
 around these problems:</p></li>
 </ol>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>config APPSDIR
     string
 -   option env=&quot;APPSDIR&quot;
 +   default &quot;../apps&quot;
 </pre></div>
 </div>
 </li>
 </ol>
 </section>
 </section>
 <section id="toolchains">
 <h2>TOOLCHAINS<a class="headerlink" href="#toolchains" title="Permalink to this heading"></a></h2>
 <section id="cross-development-toolchains">
 <h3>Cross-Development Toolchains<a class="headerlink" href="#cross-development-toolchains" title="Permalink to this heading"></a></h3>
 <blockquote>
 <div><p>In order to build NuttX for your board, you will have to obtain a cross-
 compiler to generate code for your target CPU.  For each board,
 configuration, there is a <code class="docutils literal notranslate"><span class="pre">README.txt</span></code> file (at
 <code class="docutils literal notranslate"><span class="pre">boards/&lt;arch-name&gt;/&lt;chip-name&gt;/&lt;board-name&gt;/README.txt</span></code>).
 That README file contains suggestions and information about appropriate
 tools and development environments for use with your board.</p>
 <p>In any case, the PATH environment variable will need to be updated to
 include the location where the build can find the toolchain binaries.</p>
 </div></blockquote>
 </section>
 <section id="nuttx-buildroot-toolchain">
 <h3>NuttX Buildroot Toolchain<a class="headerlink" href="#nuttx-buildroot-toolchain" title="Permalink to this heading"></a></h3>
 <blockquote>
 <div><p>For many configurations, a DIY set of tools is available for NuttX.  These
 tools can be downloaded from the NuttX Bitbucket.org file repository.  After
 unpacking the buildroot tarball, you can find instructions for building
 the tools in the <code class="docutils literal notranslate"><span class="pre">buildroot/boards/README.txt</span></code> file.</p>
 <p>Check the README.txt file in the configuration directory for your board
 to see if you can use the buildroot toolchain with your board (this
 README.txt file is located in
 <code class="docutils literal notranslate"><span class="pre">boards/&lt;arch-name&gt;/&lt;chip-name&gt;/&lt;board-name&gt;/README.txt</span></code>).</p>
 <p>This toolchain is available for both the Linux and Cygwin development
 environments.</p>
 <p>Advantages:  (1) NuttX header files are built into the tool chain,
 and (2) related support tools like NXFLAT tools, the ROMFS
 genromfs tools, and the kconfig-frontends tools can be built into your
 toolchain.</p>
 <p>Disadvantages:  This tool chain is not was well supported as some other
 toolchains.  GNU tools are not my priority and so the buildroot tools
 often get behind.  For example, until recently there was no EABI support
 in the NuttX buildroot toolchain for ARM.</p>
 <p>NOTE: For Cortex-M3/4, there are OABI and EABI versions of the buildroot
 toolchains.  If you are using the older OABI toolchain the prefix for
 the tools will be <code class="docutils literal notranslate"><span class="pre">arm-nuttx-elf-</span></code>; for the EABI toolchain the prefix will
 be <code class="docutils literal notranslate"><span class="pre">arm-nuttx-eabi-</span></code>. If you are using the older OABI toolchain with
 an ARM Cortex-M3/4, you will need to set CONFIG_ARM_TOOLCHAIN_BUILDROOT_OABI
 in the <code class="docutils literal notranslate"><span class="pre">.config</span></code> file in order to pick the right tool prefix.</p>
 <p>If the make system ever picks the wrong prefix for your toolchain, you
 can always specify the prefix on the command to override the default
 like:</p>
 </div></blockquote>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>make CROSSDEV=arm-nuttx-elf
 </pre></div>
 </div>
 </section>
 </section>
 <section id="shells">
 <h2>SHELLS<a class="headerlink" href="#shells" title="Permalink to this heading"></a></h2>
 <p>The NuttX build relies on some shell scripts.  Some are inline in the
 Makefiles and many are executable scripts in the <code class="docutils literal notranslate"><span class="pre">tools/</span></code>. directory.  The
 scripts were all developed using bash and many contain bash shell
 dependencies.</p>
 <p>Most of the scripts begin with <code class="docutils literal notranslate"><span class="pre">#!/bin/bash</span></code> to specifically select the
 bash shell.  Some still have <code class="docutils literal notranslate"><span class="pre">#!/bin/sh</span></code> but I haven’t heard any complaints
 so these must not have bash dependencies.</p>
 <p>There are two shell issues that I have heard of:</p>
 <ol class="arabic">
 <li><p>Linux where <code class="docutils literal notranslate"><span class="pre">/bin/sh</span></code> refers to an incompatible shell (like <code class="docutils literal notranslate"><span class="pre">ksh</span></code> or <code class="docutils literal notranslate"><span class="pre">csh</span></code>).</p>
 <p>In this case, bash is probably available and the <code class="docutils literal notranslate"><span class="pre">#!/bin/bash</span></code> at the
 beginning of the file should do the job.  If any scripts with <code class="docutils literal notranslate"><span class="pre">#!/bin/sh</span></code>
 fail, try changing that to <code class="docutils literal notranslate"><span class="pre">#!/bin/bash</span></code> and let me know about the change.</p>
 </li>
 <li><p>FreeBSD with the Bourne Shell and no bash shell.</p>
 <p>The other, reverse case has also been reported on FreeBSD setups that
 have the Bourne shell, but not bash.  In this base, <code class="docutils literal notranslate"><span class="pre">#!/bin/bash</span></code> fails
 but <code class="docutils literal notranslate"><span class="pre">#!/bin/sh</span></code> works okay.  My recommendation in this case is to create
 a symbolic link at <code class="docutils literal notranslate"><span class="pre">/bin/bash</span></code> that refers to the Bourne shell.</p>
 <p>There may still be issues, however, with certain the <code class="docutils literal notranslate"><span class="pre">bash</span></code>-centric scripts
 that will require modifications.</p>
 </li>
 </ol>
 </section>
 <section id="building-nuttx">
 <h2>BUILDING NUTTX<a class="headerlink" href="#building-nuttx" title="Permalink to this heading"></a></h2>
 <section id="building">
 <h3>Building<a class="headerlink" href="#building" title="Permalink to this heading"></a></h3>
 <p>NuttX builds in-place in the source tree.  You do not need to create
 any special build directories.  Assuming that your Make.defs is setup
 properly for your tool chain and that PATH environment variable contains
 the path to where your cross-development tools are installed, the
 following steps are all that are required to build NuttX:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>cd {TOPDIR}
 make
 </pre></div>
 </div>
 <p>At least one configuration (eagle100) requires additional command line
 arguments on the make command.  Read
 <code class="docutils literal notranslate"><span class="pre">{TOPDIR}/boards/&lt;arch-name&gt;/&lt;chip-name&gt;/&lt;board-name&gt;/README.txt</span></code> to see
 if that applies to your target.</p>
 </section>
 <section id="re-building">
 <h3>Re-building<a class="headerlink" href="#re-building" title="Permalink to this heading"></a></h3>
 <p>Re-building is normally simple – just type make again.</p>
 <p>But there are some things that can “get you” when you use the Cygwin
 development environment with Windows native tools.  The native Windows
 tools do not understand Cygwin’s symbolic links, so the NuttX make system
 does something weird:  It copies the configuration directories instead of
 linking to them (it could, perhaps, use the NTFS <code class="docutils literal notranslate"><span class="pre">mklink</span></code> command, but it
 doesn’t).</p>
 <p>A consequence of this is that you can easily get confused when you edit
 a file in one of the linked (i.e., copied) directories, re-build NuttX,
 and then not see your changes when you run the program.  That is because
 build is still using the version of the file in the copied directory, not
 your modified file!</p>
 <p>Older versions of NuttX did not support dependencies in this
 configuration.  So a simple work around this annoying behavior in this
 case was the following when you re-build:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>make clean_context all
 </pre></div>
 </div>
 <p>This ‘make’ command will remove of the copied directories, re-copy them,
 then make NuttX.</p>
 <p>However, more recent versions of NuttX do support dependencies for the
 Cygwin build.  As a result, the above command will cause everything to be
 rebuilt (because it removes and will cause recreating the
 <code class="docutils literal notranslate"><span class="pre">include/nuttx/config.h</span></code> header file).  A much less gracefully but still
 effective command in this case is the following for the ARM configuration:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>rm -rf arch/arm/src/chip arch/arm/src/board
 </pre></div>
 </div>
 <p>This “kludge” simple removes the copied directories.  These directories
 will be re-created when you do a normal ‘make’ and your edits will then be
 effective.</p>
 </section>
 <section id="build-targets-and-options">
 <h3>Build Targets and Options<a class="headerlink" href="#build-targets-and-options" title="Permalink to this heading"></a></h3>
 <section id="build-targets">
 <h4>Build Targets<a class="headerlink" href="#build-targets" title="Permalink to this heading"></a></h4>
 <p>Below is a summary of the build targets available in the top-level
 NuttX Makefile:</p>
 <ul>
 <li><p><code class="docutils literal notranslate"><span class="pre">all</span></code></p>
 <p>The default target builds the NuttX executable in the selected output
 formats.</p>
 </li>
 <li><p><code class="docutils literal notranslate"><span class="pre">clean</span></code></p>
 <p>Removes derived object files, archives, executables, and temporary
 files, but retains the configuration and context files and directories.</p>
 </li>
 <li><p><code class="docutils literal notranslate"><span class="pre">distclean</span></code></p>
 <p>Does ‘clean’ then also removes all configuration and context files.
 This essentially restores the directory structure to its original,
 unconfigured stated.</p>
 </li>
 </ul>
 <p>Application housekeeping targets.  The APPDIR variable refers to the user
 application directory.  A sample <code class="docutils literal notranslate"><span class="pre">apps/</span></code> directory is included with NuttX,
 however, this is not treated as part of NuttX and may be replaced with a
 different application directory.  For the most part, the application
 directory is treated like any other build directory in the <code class="docutils literal notranslate"><span class="pre">Makefile</span></code> script.
 However, as a convenience, the following targets are included to support
 housekeeping functions in the user application directory from the NuttX
 build directory.</p>
 <ul>
 <li><p><code class="docutils literal notranslate"><span class="pre">apps_clean</span></code></p>
 <p>Perform the clean operation only in the user application directory</p>
 </li>
 <li><p><code class="docutils literal notranslate"><span class="pre">apps_distclean</span></code></p>
 <p>Perform the distclean operation only in the user application directory.
 The apps/.config file is preserved so that this is not a “full” distclean
 but more of a configuration “reset” for the application directory.</p>
 </li>
 <li><p><code class="docutils literal notranslate"><span class="pre">export</span></code></p>
 <p>The export target will package the NuttX libraries and header files into
 an exportable package.  Caveats: (1) These needs some extension for the KERNEL
 build. (2) The logic in tools/mkexport.sh only supports GCC and, for example,
 explicitly assumes that the archiver is ‘ar’</p>
 </li>
 <li><p><code class="docutils literal notranslate"><span class="pre">flash</span></code> (or <code class="docutils literal notranslate"><span class="pre">download</span></code> : DEPRECATED)</p>
 <p>This is a helper target that will rebuild NuttX and flash it to the target
 system in one step.  The operation of this target depends completely upon
 implementation of the FLASH command in the user Make.defs file.  It will
 generate an error if the FLASH command is not defined.</p>
 </li>
 </ul>
 <p>The following targets are used internally by the make logic but can be invoked
 from the command under certain conditions if necessary.</p>
 <ul>
 <li><p><code class="docutils literal notranslate"><span class="pre">depend</span></code></p>
 <p>Create build dependencies. (NOTE:  There is currently no support for build
 dependencies under Cygwin using Windows-native toolchains.)</p>
 </li>
 <li><p><code class="docutils literal notranslate"><span class="pre">context</span></code></p>
 <p>The context target is invoked on each target build to assure that NuttX is
 properly configured.  The basic configuration steps include creation of the
 the <code class="docutils literal notranslate"><span class="pre">config.h</span></code> and <code class="docutils literal notranslate"><span class="pre">version.h</span></code> header files in the <code class="docutils literal notranslate"><span class="pre">include/nuttx</span></code> directory and
 the establishment of symbolic links to configured directories.</p>
 </li>
 <li><p><code class="docutils literal notranslate"><span class="pre">clean_context</span></code></p>
 <p>This is part of the <code class="docutils literal notranslate"><span class="pre">distclean</span></code> target.  It removes all of the header files
 and symbolic links created by the context target.</p>
 </li>
 </ul>
 </section>
 <section id="build-options">
 <h4>Build Options<a class="headerlink" href="#build-options" title="Permalink to this heading"></a></h4>
 <p>Of course, the value any make variable an be overridden from the make command
 line.  However, there is one particular variable assignment option that may
 be useful to you:</p>
 <ul>
 <li><p><code class="docutils literal notranslate"><span class="pre">V=1</span></code></p>
 <p>This is the build “verbosity flag.”  If you specify <code class="docutils literal notranslate"><span class="pre">V=1</span></code> on the make command
 line, you will see the exact commands used in the build. This can be very
 useful when adding new boards or tracking down compile time errors and
 warnings (Contributed by Richard Cochran).</p>
 </li>
 </ul>
 </section>
 </section>
 <section id="native-windows-build">
 <h3>Native Windows Build<a class="headerlink" href="#native-windows-build" title="Permalink to this heading"></a></h3>
 <p>The beginnings of a Windows native build are in place but still not often
 used as of this writing.  The build was functional but because of lack of
 use may find some issues to be resolved with this build configuration.</p>
 <p>The windows native build logic initiated if CONFIG_WINDOWS_NATIVE=y is
 defined in the NuttX configuration file:</p>
 <p>This build:</p>
 <ul class="simple">
 <li><p>Uses all Windows style paths</p></li>
 <li><p>Uses primarily Windows batch commands from cmd.exe, with</p></li>
 <li><p>A few extensions from GNUWin32</p></li>
 </ul>
 <p>In this build, you cannot use a Cygwin or MSYS shell. Rather the build must
 be performed in a Windows console window. Here is a better terminal than the
 standard issue, CMD.exe terminal:  ConEmu which can be downloaded from:
 <a class="reference external" href="https://sourceforge.net/projects/conemu/">https://sourceforge.net/projects/conemu/</a> or <a class="reference external" href="https://conemu.github.io/">https://conemu.github.io/</a>.</p>
 <p>Build Tools.  The build still relies on some Unix-like commands.  I use
 the GNUWin32 tools that can be downloaded from <a class="reference external" href="http://gnuwin32.sourceforge.net/">http://gnuwin32.sourceforge.net/</a>
 using the <em>Download all</em> selection.  Individual packages can be download
 instead if you know what you are doing and want a faster download (No, I
 can’t tell you which packages you should or should not download).</p>
 <p>NOTE:  It should be possible to use Cygwin or MSYS2 in place of the GNUWin32
 tools.  There are, however, complexities in doing that because those tools
 depend on the shell environment and use DLLs that are not found (at least
 not without the correct setup).</p>
 <p>Host Compiler:  I use the MingGW GCC compiler which can be downloaded from
 <a class="reference external" href="http://www.mingw.org/">http://www.mingw.org/</a>.  If you are using GNUWin32, then it is recommended
 the you not install the optional MSYS components as there may be conflicts.</p>
 <p>Kconfig-frontends:  See the section entitled “NuttX Configuration Tool
 under DOS” for information about installing the <code class="docutils literal notranslate"><span class="pre">kconfig-frontend</span></code> tools to
 run natively under Windows.</p>
 <p>This capability should still be considered a work in progress because:</p>
 <ol class="arabic simple">
 <li><p>It has not been verified on all targets and tools, and</p></li>
 <li><p>it still lacks some of the creature-comforts of the more mature
 environments.</p></li>
 </ol>
 </section>
 <section id="installing-gnuwin32">
 <h3>Installing GNUWin32<a class="headerlink" href="#installing-gnuwin32" title="Permalink to this heading"></a></h3>
 <blockquote>
 <div><p>The Windows native build will depend upon a few Unix-like tools that can be
 provided either by MSYS or GNUWin32.  The GNUWin32 are available from
 <a class="reference external" href="http://gnuwin32.sourceforge.net/">http://gnuwin32.sourceforge.net/</a>.  GNUWin32 provides ports of tools with a
 GPL or similar open source license to modern MS-Windows (Microsoft Windows
 2000 / XP / 2003 / Vista / 2008 / 7).  See
 <a class="reference external" href="http://gnuwin32.sourceforge.net/packages.html">http://gnuwin32.sourceforge.net/packages.html</a> for a list of all of the tools
 available in the GNUWin32 package.</p>
 <p>The SourceForge project is located here:
 <a class="reference external" href="http://sourceforge.net/projects/gnuwin32/">http://sourceforge.net/projects/gnuwin32/</a>.  The project is still being
 actively supported (although some of the Windows ports have gotten very old).</p>
 <p>Some commercial toolchains include a subset of the GNUWin32 tools in the
 installation.  My recommendation is that you download the GNUWin32 tools
 directly from the sourceforge.net website so that you will know what you are
 using and can reproduce your build environment.</p>
 <p>GNUWin32 Installation Steps:</p>
 <p>The following steps will download and execute the GNUWin32 installer.</p>
 </div></blockquote>
 <ol class="arabic">
 <li><p>Download <code class="docutils literal notranslate"><span class="pre">GetGNUWin32-x.x.x.exe</span></code> from
 <a class="reference external" href="http://sourceforge.net/projects/getgnuwin32/files/">http://sourceforge.net/projects/getgnuwin32/files/</a>.  This is the
 installer.  The current version as of this writing is 0.6.3.</p></li>
 <li><p>Run the installer.</p></li>
 <li><p>Accept the license.</p></li>
 <li><p>Select the installation directory.  My recommendation is the
 directory that contains this README file (<code class="docutils literal notranslate"><span class="pre">&lt;this-directory&gt;</span></code>).</p></li>
 <li><p>After running <code class="docutils literal notranslate"><span class="pre">GetGNUWin32-0.x.x.exe</span></code>, you will have a new directory
 <code class="docutils literal notranslate"><span class="pre">&lt;this-directory&gt;/GetGNUWin32</span></code></p>
 <p>Note that the GNUWin32 installer didn’t install GNUWin32.  Instead, it
 installed another, smarter downloader.  That downloader is the GNUWin32
 package management tool developed by the Open SSL project.</p>
 <p>The following steps probably should be performed from inside a DOS shell.</p>
 </li>
 <li><p>Change to the directory created by <code class="docutils literal notranslate"><span class="pre">GetGNUWin32-x.x.x.exe</span></code></p>
 <blockquote>
 <div><p>cd GetGNUWin32</p>
 </div></blockquote>
 </li>
 <li><p>Execute the download.bat script.  The download.bat script will download
 about 446 packages!  Enough to have a very complete Linux-like environment
 under the DOS shell.  This will take awhile.  This step only downloads
 the packages and the next step will install the packages.</p>
 <blockquote>
 <div><p>download</p>
 </div></blockquote>
 </li>
 <li><p>This step will install the downloaded packages.  The argument of the
 install.bat script is the installation location.  C:gnuwin32 is the
 standard install location:</p>
 <blockquote>
 <div><p>install C:gnuwin32</p>
 </div></blockquote>
 <p><strong>NOTE</strong>:  This installation step will install <em>all</em> GNUWin32 packages… far
 more than you will ever need.  If disc space is a problem for you, you might
 need to perform a manual installation of the individual ZIP files that you
 will find in the <code class="docutils literal notranslate"><span class="pre">&lt;this</span> <span class="pre">directory&gt;/GetGNUWin32/packages</span></code> directory.</p>
 </li>
 <li><p>Make sure that you add the GNUWin32 tools to your path variable:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>set PATH=C:\gnuwin32\bin;%PATH%
 </pre></div>
 </div>
 <p><strong>WARNING</strong>:  Make sure you have <code class="docutils literal notranslate"><span class="pre">C:\MinGW\bin</span></code> in your path before any other
 directory that contains <code class="docutils literal notranslate"><span class="pre">libiconv-2.dll</span></code>. Apparently the <code class="docutils literal notranslate"><span class="pre">as.exe</span></code> in some
 MinGW distributions are dependent on that DLL, and having an old
 version of it in the path somewhere (for example GnuWin32 tools) will
 cause as.exe to pick up the older version that doesn’t have the entry
 point it’s looking for.</p>
 </li>
 </ol>
 </section>
 </section>
 <section id="cygwin-build-problems">
 <h2>CYGWIN BUILD PROBLEMS<a class="headerlink" href="#cygwin-build-problems" title="Permalink to this heading"></a></h2>
 <section id="performance">
 <h3>Performance<a class="headerlink" href="#performance" title="Permalink to this heading"></a></h3>
 <p>Build performance under Cygwin is really not so bad, certainly not as good
 as a Linux build.  However, often you will find that the performance is
 not just bad but terrible.  If you are seeing awful performance.. like two
 or three compilations per second.. the culprit is usually your Windows
 Anti-Virus protection interfering with the build tool program execution.</p>
 <p>I use Cygwin quite often and I use Windows Defender.  In order to get good
 build performance, I routinely keep the Windows Defender “Virus &amp; Threat
 Protections Settings” screen up:  I disable “Real-Time Protection” just
 before entering ‘make’ then turn “Real-Time Protection” back on when the
 build completes.  With this additional nuisance step, I find that build
 performance under Cygwin is completely acceptable.</p>
 </section>
 <section id="strange-path-problems">
 <h3>Strange Path Problems<a class="headerlink" href="#strange-path-problems" title="Permalink to this heading"></a></h3>
 <p>If you see strange behavior when building under Cygwin then you may have
 a problem with your PATH variable.  For example, if you see failures to
 locate files that are clearly present, that may mean that you are using
 the wrong version of a tool.  For example, you may not be using Cygwin’s
 ‘make’ program at /usr/bin/make.  Try:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>which make
 /usr/bin/make
 </pre></div>
 </div>
 <p>When you install some toolchains (such as Yargarto or CodeSourcery tools),
 they may modify your PATH variable to include a path to their binaries.
 At that location, they may have GNUWin32 versions of the tools.  So you
 might actually be using a version of make that does not understand Cygwin
 paths.</p>
 <p>The solution is either:</p>
 <ol class="arabic">
 <li><p>Edit your PATH to remove the path to the GNUWin32 tools, or</p></li>
 <li><p>Put /usr/local/bin, /usr/bin, and /bin at the front of your path:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>export PATH=/usr/local/bin:/usr/bin:/bin:$PATH
 </pre></div>
 </div>
 </li>
 </ol>
 </section>
 <section id="window-native-toolchain-issues">
 <h3>Window Native Toolchain Issues<a class="headerlink" href="#window-native-toolchain-issues" title="Permalink to this heading"></a></h3>
 <p>There are many popular Windows native toolchains that may be used with NuttX.
 Examples include CodeSourcery (for Windows), devkitARM, and several vendor-
 provided toolchains.  There are several limitations with using a and Windows
 based toolchain in a Cygwin environment.  The three biggest are:</p>
 <ol class="arabic">
 <li><p>The Windows toolchain cannot follow Cygwin paths.  Path conversions are
 performed automatically in the Cygwin makefiles using the ‘cygpath’ utility
 but you might easily find some new path problems.  If so, check out ‘cygpath -w’</p></li>
 <li><p>Windows toolchains cannot follow Cygwin symbolic links.  Many symbolic links
 are used in NuttX (e.g., include/arch).  The make system works around these
 problems for the Windows tools by copying directories instead of linking them.
 But this can also cause some confusion for you:  For example, you may edit
 a file in a “linked” directory and find that your changes had no effect.
 That is because you are building the copy of the file in the “fake” symbolic
 directory.  If you use a Windows toolchain, you should get in the habit of
 making like this:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>make clean_context all
 </pre></div>
 </div>
 <p>An alias in your .bashrc file might make that less painful.  The rebuild
 is not a long as you might think because there is no dependency checking
 if you are using a native Windows toolchain.  That bring us to #3:</p>
 </li>
 </ol>
 </section>
 <section id="general-pre-built-toolchain-issues">
 <h3>General Pre-built Toolchain Issues<a class="headerlink" href="#general-pre-built-toolchain-issues" title="Permalink to this heading"></a></h3>
 <p>To continue with the list of “Window Native Toolchain Issues” we can add
 the following.  These, however, are really just issues that you will have
 if you use any pre-built toolchain (vs. building the NuttX toolchain from
 the NuttX buildroot package):</p>
 <p>There may be incompatibilities with header files, libraries, and compiler
 built-in functions detailed below.  For the most part, these issues
 are handled in the existing make logic.  But if you are breaking new ground,
 then you may encounter these:</p>
 <ol class="arabic">
 <li><p>Header Files.  Most pre-built toolchains will build with a foreign C
 library (usually newlib, but maybe uClibc or glibc if you are using a
 Linux toolchain).  This means that the header files from the foreign
 C library will be built into the toolchain.  So if you <code class="docutils literal notranslate"><span class="pre">#include</span> <span class="pre">&lt;stdio.h&gt;</span></code>,
 you will get the stdio.h from the incompatible, foreign C library and
 not the nuttx <code class="docutils literal notranslate"><span class="pre">stdio.h</span></code> (at <code class="docutils literal notranslate"><span class="pre">nuttx/include/stdio.h</span></code>) that you wanted.</p>
 <p>This can cause confusion in the builds and you must always be
 sure the <code class="docutils literal notranslate"><span class="pre">-nostdinc</span></code> is included in the <code class="docutils literal notranslate"><span class="pre">CFLAGS</span></code>.  That will assure that
 you take the include files only from</p>
 </li>
 <li><p>Libraries.  What was said above header files applies to libraries.
 You do not want to include code from the libraries of any foreign
 C libraries built into your toolchain.  If this happens you will get
 perplexing errors about undefined symbols.  To avoid these errors,
 you will need to add <code class="docutils literal notranslate"><span class="pre">-nostdlib</span></code> to your <code class="docutils literal notranslate"><span class="pre">CFLAGS</span></code> flags to assure that
 you only take code from the NuttX libraries.</p>
 <p>This, however, may causes other issues for libraries in the toolchain
 that you do want (like <code class="docutils literal notranslate"><span class="pre">libgcc.a</span></code> or <code class="docutils literal notranslate"><span class="pre">libm.a</span></code>).  These are special-cased
 in most Makefiles, but you could still run into issues of missing
 libraries.</p>
 </li>
 <li><p>Built-Ins.  Some compilers target a particular operating system.
 Many people would, for example, like to use the same toolchain to
 develop Linux and NuttX software.  Compilers built for other
 operating systems may generate incompatible built-in logic and,
 for this reason, <code class="docutils literal notranslate"><span class="pre">-fno-builtin</span></code> should also be included in your
 C flags</p>
 <p>And finally you may not be able to use NXFLAT.</p>
 </li>
 <li><p>NXFLAT. If you use a pre-built toolchain, you will lose all support
 for NXFLAT.  NXFLAT is a binary format described in
 Documentation/NuttXNxFlat.html.  It may be possible to build
 standalone versions of the NXFLAT tools; there are a few examples
 of this in the buildroot repository at <a class="reference external" href="https://bitbucket.org/nuttx/buildroot">https://bitbucket.org/nuttx/buildroot</a>
 However, it is possible that there could be interoperability issues
 with your toolchain since they will be using different versions of
 binutils and possibly different ABIs.</p></li>
 </ol>
 </section>
 <section id="building-original-linux-boards-in-cygwin">
 <h3>Building Original Linux Boards in Cygwin<a class="headerlink" href="#building-original-linux-boards-in-cygwin" title="Permalink to this heading"></a></h3>
 <p>Some default board configurations are set to build under Linux and others
 to build under Windows with Cygwin.  Various default toolchains may also
 be used in each configuration.  It is possible to change the default
 setup.  Here, for example, is what you must do in order to compile a
 default Linux configuration in the Cygwin environment using the
 CodeSourcery for Windows toolchain.  After instantiating a “canned”
 NuttX configuration, run the target ‘menuconfig’ and set the following
 items:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>Build Setup-&gt;Build Host Platform-&gt;Windows
 Build Setup-&gt;Windows Build Environment-&gt;Cygwin
 System Type-&gt;Toolchain Selection-&gt;CodeSourcery GNU Toolchain under Windows
 </pre></div>
 </div>
 <p>In Windows 7 it may be required to open the Cygwin shell as Administrator
 (“Run As” option, right button) you find errors like “Permission denied”.</p>
 </section>
 <section id="recovering-from-bad-configurations">
 <h3>Recovering from Bad Configurations<a class="headerlink" href="#recovering-from-bad-configurations" title="Permalink to this heading"></a></h3>
 <p>Many people make the mistake of configuring NuttX with the “canned”
 configuration and then just typing <code class="docutils literal notranslate"><span class="pre">make</span></code> with disastrous consequences;
 the build may fail with mysterious, uninterpretable, and irrecoverable
 build errors.  If, for example, you do this with an unmodified Linux
 configuration in a Windows/Cgwin environment, you will corrupt the
 build environment.  The environment will be corrupted because of POSIX vs
 Windows path issues and with issues related to symbolic links.  If you
 make the mistake of doing this, the easiest way to recover is to just
 start over: Do <code class="docutils literal notranslate"><span class="pre">make</span> <span class="pre">distclean</span></code> to remove every trace of the corrupted
 configuration, reconfigure from scratch, and make certain that the set
 the configuration correctly for your platform before attempting to make
 again.</p>
 <p>Just fixing the configuration file after you have instantiated the bad
 configuration with ‘make’ is not enough.</p>
 </section>
 </section>
 <section id="documentation">
 <h2>DOCUMENTATION<a class="headerlink" href="#documentation" title="Permalink to this heading"></a></h2>
 <p>Additional information can be found in the Documentation/ directory and
 also in README files that are scattered throughout the source tree.  The
 documentation is in HTML and can be access by loading the following file
 into your Web browser:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>Documentation/index.html
 </pre></div>
 </div>
 <p>NuttX documentation is also available online at <a class="reference external" href="https://nuttx.apache.org/">https://nuttx.apache.org/</a>.</p>
 <p>Below is a guide to the available README files in the NuttX source tree:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>nuttx/
  |
  |- arch/
  |   |
  |   |- arm/
  |   |   `- src
  |   |       |- common
  |   |       |   `- README_lwl_console.txt
  |   |       |- lpc214x
  |   |       |    `-README.txt
  |   |       `- stm32l4
  |   |           `- README.txt
  |   |- renesas/
  |   |   |- include/
  |   |   |   `-README.txt
  |   |   |- src/
  |   |   |   `-README.txt
  |   |- x86/
  |   |   |- include/
  |   |   |   `-README.txt
  |   |   `- src/
  |   |       `-README.txt
  |   `- z80/
  |   |   `- src/
  |   |       |- z80/README.txt
  |   |       `- z180/README.txt, z180_mmu.txt
  |   `- README.txt
  |- audio/
  |   `-README.txt
  |- boards/
  |   |- arm/
  |   |   |- a1x/
  |   |   |   `- pcduino-a10/
  |   |   |       `- README.txt
  |   |   |- am335x/
  |   |   |   `- beaglebone-black/
  |   |   |       `- README.txt
  |   |   |- c5471/
  |   |   |   `- c5471evm/
  |   |   |       `- README.txt
  |   |   |- cxd56xx/
  |   |   |   `- spresense/
  |   |   |       `- README.txt
  |   |   |- dm320/
  |   |   |   `- ntosd-dm320/
  |   |   |       |- doc/README.txt
  |   |   |       `- README.txt
  |   |   |- efm32/
  |   |   |   |- efm32-g8xx-stk/
  |   |   |   |   `- README.txt
  |   |   |   |- efm32gg-stk3700/
  |   |   |   |   `- README.txt
  |   |   |   `- olimex-efm32g880f128-stk/
  |   |   |       `- README.txt
  |   |   |- imx6/
  |   |   |   `- sabre-6quad/
  |   |   |       `- README.txt
  |   |   |- imxrt/
  |   |   |   |- imxrt1050-evk/
  |   |   |   |   `- README.txt
  |   |   |   |- imxrt1060-evk/
  |   |   |   |   `- README.txt
  |   |   |   `- teensy-4.x/
  |   |   |       `- README.txt
  |   |   |- kinetis/
  |   |   |   |- freedom-k28f/
  |   |   |   |   `- README.txt
  |   |   |   |- freedom-k64f/
  |   |   |   |   `- README.txt
  |   |   |   |- freedom-k66f/
  |   |   |   |   `- README.txt
  |   |   |   |- kwikstik-k40/
  |   |   |   |   `- README.txt
  |   |   |   |- teensy-3.x/
  |   |   |   |   `- README.txt
  |   |   |   |- twr-k60n512/
  |   |   |   |   `- README.txt
  |   |   |   `- twr-k64f120m/
  |   |   |       `- README.txt
  |   |   |- kl/
  |   |   |   |- freedom-kl25z/
  |   |   |   |   `- README.txt
  |   |   |   |- freedom-kl26z/
  |   |   |   |   `- README.txt
  |   |   |   `- teensy-lc/
  |   |   |       `- README.txt
  |   |   |- lc823450/
  |   |   |   `- lc823450-xgevk/
  |   |   |       `- README.txt
  |   |   |- lpc17xx_40xx/
  |   |   |   |- lincoln60/
  |   |   |   |   `- README.txt
  |   |   |   |- lpc4088-devkit/
  |   |   |   |   `- README.txt
  |   |   |   |- lpc4088-quickstart/
  |   |   |   |   `- README.txt
  |   |   |   |- lpcxpresso-lpc1768/
  |   |   |   |   `- README.txt
  |   |   |   |- lx_cpu/
  |   |   |   |   `- README.txt
  |   |   |   |- mbed/
  |   |   |   |   `- README.txt
  |   |   |   |- mcb1700/
  |   |   |   |   `- README.txt
  |   |   |   |- olimex-lpc1766stk/
  |   |   |   |   `- README.txt
  |   |   |   |- open1788/
  |   |   |   |   `- README.txt
  |   |   |   |- pnev5180b/
  |   |   |   |   `- README.txt
  |   |   |   |- u-blox-c027/
  |   |   |   |   `- README.txt
  |   |   |   `- zkit-arm-1769/
  |   |   |       `- README.txt
  |   |   |- lpc214x/
  |   |   |   |- mcu123-lpc214x/
  |   |   |   |   `- README.txt
  |   |   |   `- zp214xpa/
  |   |   |       `- README.txt
  |   |   |- lpc2378/
  |   |   |   `- olimex-lpc2378/
  |   |   |       `- README.txt
  |   |   |- lpc31xx/
  |   |   |   |- ea3131/
  |   |   |   |   `- README.txt
  |   |   |   |- ea3152/
  |   |   |   |   `- README.txt
  |   |   |   `- olimex-lpc-h3131/
  |   |   |       `- README.txt
  |   |   |- lpc43xx/
  |   |   |   |- bambino-200e/
  |   |   |   |   `- README.txt
  |   |   |   |- lpc4330-xplorer/
  |   |   |   |   `- README.txt
  |   |   |   |- lpc4337-ws/
  |   |   |   |   `- README.txt
  |   |   |   |- lpc4357-evb/
  |   |   |   |   `- README.txt
  |   |   |   `- lpc4370-link2/
  |   |   |       `- README.txt
  |   |   |- lpc54xx/
  |   |   |   `- lpcxpresso-lpc54628/
  |   |   |       `- README.txt
  |   |   |- max326xx/
  |   |   |   `- max32660-evsys/
  |   |   |       `- README.txt
  |   |   |- moxart/
  |   |   |   `- moxa/
  |   |   |- nrf52/
  |   |   |   `- nrf52-generic/
  |   |   |       `- README.txt
  |   |   |- nuc1xx/
  |   |   |   `- nutiny-nuc120/
  |   |   |       `- README.txt
  |   |   |- s32k1xx/
  |   |   |   |- s32k118evb/
  |   |   |   |   `- README.txt
  |   |   |   |- s32k146evb/
  |   |   |   |   `- README.txt
  |   |   |   `- s32k148evb/
  |   |   |       `- README.txt
  |   |   |- sam34/
  |   |   |   |- arduino-due/
  |   |   |   |   `- README.txt
  |   |   |   |- flipnclick-sam3x/
  |   |   |   |   `- README.txt
  |   |   |   |- sam3u-ek/
  |   |   |   |   `- README.txt
  |   |   |   |- sam4cmp-db/
  |   |   |   |   `- README.txt
  |   |   |   |- sam4e-ek/
  |   |   |   |   `- README.txt
  |   |   |   |- sam4l-xplained/
  |   |   |   |   `- README.txt
  |   |   |   |- sam4s-xplained/
  |   |   |   |   `- README.txt
  |   |   |   `- sam4s-xplained-pro/
  |   |   |       `- README.txt
  |   |   |- sama5/
  |   |   |   |- sama5d2-xult/
  |   |   |   |   `- README.txt
  |   |   |   |- giant-board/
  |   |   |   |   `- README.md
  |   |   |   |- sama5d3x-ek/
  |   |   |   |   `- README.txt
  |   |   |   |- sama5d3-xplained/
  |   |   |   |   `- README.txt
  |   |   |   `- sama5d4-ek/
  |   |   |       `- README.txt
  |   |   |- samd2l2/
  |   |   |   |- arduino-m0/
  |   |   |   |   `- README.txt
  |   |   |   |- samd20-xplained/
  |   |   |   |   `- README.txt
  |   |   |   |- samd21-xplained/
  |   |   |   |   `- README.txt
  |   |   |   `- saml21-xplained/
  |   |   |       `- README.txt
  |   |   |- samd5e5/
  |   |   |   `- metro-m4/
  |   |   |      `- README.txt
  |   |   |- samv7/
  |   |   |   |- same70-qmtech/
  |   |   |   |   `- README.txt
  |   |   |   |- same70-xplained/
  |   |   |   |   `- README.txt
  |   |   |   `- samv71-xult/
  |   |   |      `- README.txt
  |   |   |- stm32/
  |   |   |   |- axoloti/
  |   |   |   |   `- README.txt
  |   |   |   |- b-g474e-dpow1/
  |   |   |   |   `- README.txt
  |   |   |   |- clicker2-stm32/
  |   |   |   |   `- README.txt
  |   |   |   |- cloudctrl/
  |   |   |   |   `- README.txt
  |   |   |   |- emw3162/
  |   |   |   |   `- README.txt
  |   |   |   |- fire-stm32v2/
  |   |   |   |   `- README.txt
  |   |   |   |- hymini-stm32v/
  |   |   |   |   `- README.txt
  |   |   |   |- maple/
  |   |   |   |   `- README.txt
  |   |   |   |- mikroe-stm32f4/
  |   |   |   |   `- README.txt
  |   |   |   |- nucleo-f103rb/
  |   |   |   |   `- README.txt
  |   |   |   |- nucleo-f207zg/
  |   |   |   |   `- README.txt
  |   |   |   |- nucleo-f302r8/
  |   |   |   |   `- README.txt
  |   |   |   |- nucleo-f303re/
  |   |   |   |   `- README.txt
  |   |   |   |- nucleo-f303ze/
  |   |   |   |   `- README.txt
  |   |   |   |- nucleo-f334r8/
  |   |   |   |   `- README.txt
  |   |   |   |- nucleo-f410rb/
  |   |   |   |   `- README.txt
  |   |   |   |- nucleo-f446re/
  |   |   |   |   `- README.txt
  |   |   |   |- nucleo-f4x1re/
  |   |   |   |   `- README.txt
  |   |   |   |- nucleo-l152re/
  |   |   |   |   `- README.txt
  |   |   |   |- olimexino-stm32/
  |   |   |   |- olimex-stm32-e407/
  |   |   |   |   `- README.txt
  |   |   |   |- olimex-stm32-h405/
  |   |   |   |   `- README.txt
  |   |   |   |- olimex-stm32-h407/
  |   |   |   |   `- README.txt
  |   |   |   |- olimex-stm32-p107/
  |   |   |   |- olimex-stm32-p207/
  |   |   |   |   `- README.txt
  |   |   |   |- olimex-stm32-p407/
  |   |   |   |   `- README.txt
  |   |   |   |- omnibusf4/
  |   |   |   |   `- README.txt
  |   |   |   |- photon/
  |   |   |   |   `- README.txt
  |   |   |   |- shenzhou/
  |   |   |   |   `- README.txt
  |   |   |   |- stm32_tiny/
  |   |   |   |   `- README.txt
  |   |   |   |- stm3210e-eval/
  |   |   |   |   `- README.txt
  |   |   |   |- stm3220g-eval/
  |   |   |   |   `- README.txt
  |   |   |   |- stm3240g-eval/
  |   |   |   |   `- README.txt
  |   |   |   |- stm32butterfly2/
  |   |   |   |- stm32f103-minimum/
  |   |   |   |   `- README.txt
  |   |   |   |- stm32f334-disco/
  |   |   |   |   `- README.txt
  |   |   |   |- stm32f3discovery/
  |   |   |   |   `- README.txt
  |   |   |   |- stm32f411e-disco/
  |   |   |   |   `- README.txt
  |   |   |   |- stm32f429i-disco/
  |   |   |   |   `- README.txt
  |   |   |   |- stm32f4discovery/
  |   |   |   |   `- README.txt
  |   |   |   |- stm32ldiscovery/
  |   |   |   |   `- README.txt
  |   |   |   |- stm32vldiscovery/
  |   |   |   |   `- README.txt
  |   |   |   `- viewtool-stm32f107/
  |   |   |       `- README.txt
  |   |   |- stm32f0l0g0/
  |   |   |   |- b-l072z-lrwan1/
  |   |   |   |   `- README.txt
  |   |   |   |- nucleo-f072rb/
  |   |   |   |   `- README.txt
  |   |   |   |- nucleo-f091rc/
  |   |   |   |   `- README.txt
  |   |   |   |- nucleo-g070rb/
  |   |   |   |   `- README.txt
  |   |   |   |- nucleo-g071rb/
  |   |   |   |   `- README.txt
  |   |   |   |- nucleo-l073rz/
  |   |   |   |   `- README.txt
  |   |   |   |- stm32f051-discovery/
  |   |   |   |   `- README.txt
  |   |   |   `- stm32f072-discovery/
  |   |   |       `- README.txt
  |   |   |- stm32f7/
  |   |   |   |- nucleo-144/
  |   |   |   |   `- README.txt
  |   |   |   |- stm32f746g-disco/
  |   |   |   |   |- configs/fb/README.txt
  |   |   |   |   |- configs/nxdemo/README.txt
  |   |   |   |   |- configs/nxterm/README.txt
  |   |   |   |   `- README.txt
  |   |   |   |- stm32f746-ws/
  |   |   |   `- stm32f769i-disco/
  |   |   |       `- README.txt
  |   |   |- stm32h7/
  |   |   |   `- nucleo-h743zi/
  |   |   |       `- README.txt
  |   |   |- stm32l4/
  |   |   |   |- b-l475e-iot01a/
  |   |   |   |   `- README.txt
  |   |   |   |- nucleo-l432kc/
  |   |   |   |   `- README.txt
  |   |   |   |- nucleo-l452re/
  |   |   |   |   `- README.txt
  |   |   |   |- nucleo-l476rg/
  |   |   |   |   `- README.txt
  |   |   |   |- nucleo-l496zg/
  |   |   |   |   `- README.txt
  |   |   |   |- stm32l476-mdk/
  |   |   |   |   `- README.txt
  |   |   |   |- stm32l476vg-disco/
  |   |   |   |   `- README.txt
  |   |   |   `- stm32l4r9ai-disco/
  |   |   |       `- README.txt
  |   |   |- str71x/
  |   |   |   `- olimex-strp711/
  |   |   |       `- README.txt
  |   |   |- tiva/
  |   |   |   |- dk-tm4c129x/
  |   |   |   |   `- README.txt
  |   |   |   |- eagle100/
  |   |   |   |   `- README.txt
  |   |   |   |- ekk-lm3s9b96/
  |   |   |   |   `- README.txt
  |   |   |   |- launchxl-cc1310/
  |   |   |   |   `- README.txt
  |   |   |   |- launchxl-cc1312r1/
  |   |   |   |   `- README.txt
  |   |   |   |- lm3s6432-s2e/
  |   |   |   |   `- README.txt
  |   |   |   |- lm3s6965-ek/
  |   |   |   |   `- README.txt
  |   |   |   |- lm3s8962-ek/
  |   |   |   |   `- README.txt
  |   |   |   |- lm4f120-launchpad/
  |   |   |   |   `- README.txt
  |   |   |   |- tm4c123g-launchpad/
  |   |   |   |   `- README.txt
  |   |   |   `- tm4c1294-launchpad/
  |   |   |       `- README.txt
  |   |   |- tms570/
  |   |   |   |- launchxl-tms57004/
  |   |   |   |   `- README.txt
  |   |   |   `- tms570ls31x-usb-kit/
  |   |   |       `- README.txt
  |   |   `- xmc4/
  |   |       `- xmc4500-relax/
  |   |           `- README.txt
  |   |- avr/
  |   |   |- at32uc3/
  |   |   |   `- avr32dev1/
  |   |   |       `- README.txt
  |   |   |- at90usb/
  |   |   |   |- micropendous3/
  |   |   |   |   `- README.txt
  |   |   |   `- teensy-2.0/
  |   |   |       `- README.txt
  |   |   `- atmega/
  |   |       |- amber/
  |   |       |   `- README.txt
  |   |       |- arduino-mega2560/
  |   |       |   `- README.txt
  |   |       `- moteino-mega/
  |   |           `- README.txt
  |   |- hc/
  |   |   `- m9s12/
  |   |       |- demo9s12ne64/
  |   |       |   `- README.txt
  |   |       `- ne64badge/
  |   |           `- README.txt
  |   |- mips/
  |   |   |- pic32mx/
  |   |   |   |- mirtoo/
  |   |   |   |   `- README.txt
  |   |   |   |- pic32mx7mmb/
  |   |   |   |   `- README.txt
  |   |   |   |- pic32mx-starterkit/
  |   |   |   |   `- README.txt
  |   |   |   |- sure-pic32mx/
  |   |   |   |   `- README.txt
  |   |   |   `- ubw32/
  |   |   |       `- README.txt
  |   |   `-pic32mz/
  |   |       |- chipkit-wifire/
  |   |       |   `- README.txt
  |   |       |- flipnclick-pic32mz/
  |   |       |   `- README.txt
  |   |       `- pic32mz-starterkit/
  |   |           `- README.txt
  |   |- misoc/
  |   |   `- lm32/
  |   |       `- misoc/
  |   |           `- README.txt
  |   |- or1k/
  |   |   `- mor1kx/
  |   |       `- or1k/
  |   |           `- README.txt
  |   |- renesas/
  |   |   |- m16c/
  |   |   |   `- skp16c26/
  |   |   |       `- README.txt
  |   |   `-sh1/
  |   |       `- us7032evb1/
  |   |           `- README.txt
  |   |- risc-v/
  |   |- sim/
  |   |   `- sim/
  |   |       `- sim/
  |   |           |- include/README.txt
  |   |           `- README.txt
  |   |- x86/
  |   |   `- qemu/
  |   |       `- qemu-i486/
  |   |           `- README.txt
  |   |- xtensa/
  |   |   `- esp32/
  |   |       `- esp32-core/
  |   |           `- README.txt
  |   |- z16/
  |   |   `- z16f/
  |   |       `- z16f2800100zcog/
  |   |           |- configs/nsh/README.txt
  |   |           |- configs/ostest/README.txt
  |   |           |- configs/pashello/README.txt
  |   |           `- README.txt
  |   |- z80/
  |   |   |- ez80/
  |   |   |   |- ez80f910200kitg/
  |   |   |   |   |- configs/ostest/README.txt
  |   |   |   |   `- README.txt
  |   |   |   |- ez80f910200zco/
  |   |   |   |   |- configs/dhcpd/README.txt
  |   |   |   |   |- configs/httpd/README.txt
  |   |   |   |   |- configs/nettest/README.txt
  |   |   |   |   |- configs/nsh/README.txt
  |   |   |   |   |- configs/poll/README.txt
  |   |   |   |   `- README.txt
  |   |   |   |- makerlisp/
  |   |   |   |   |- configs/nsh_flash/README.txt
  |   |   |   |   |- configs/nsh_ram/README.txt
  |   |   |   |   |- configs/sdboot/README.txt
  |   |   |   |   `- README.txt
  |   |   |   `- z80x/
  |   |   |       |- configs/nsh_flash/README.txt
  |   |   |       |- configs/nsh_ram/README.txt
  |   |   |       |- configs/sdboot/README.txt
  |   |   |       `- README.txt
  |   |   |- z180/
  |   |   |   `- p112/
  |   |   |       `- README.txt
  |   |   |- z8/
  |   |   |   |- z8encore000zco/
  |   |   |   |   |- configs/ostest/README.txt
  |   |   |   |   `- README.txt
  |   |   |   `- z8f64200100kit/
  |   |   |       |- configs/ostest/README.txt
  |   |   |       `- README.txt
  |   |   `- z80/
  |   |       `- z80sim/
  |   |           `- README.txt
  |   `-README.txt
  |- drivers/
  |   |- eeprom/
  |   |   `- README.txt
  |   |- lcd/
  |   |   | README.txt
  |   |   `- pcf8574_lcd_backpack_readme.txt
  |   |- mtd/
  |   |   `- README.txt
  |   |- sensors/
  |   |   `- README.txt
  |   |- syslog/
  |   |   `- README.txt
  |   `- README.txt
  |- fs/
  |   |- binfs/
  |   |   `- README.txt
  |   |- cromfs/
  |   |   `- README.txt
  |   |- mmap/
  |   |   `- README.txt
  |   |- nxffs/
  |   |   `- README.txt
  |   |- smartfs/
  |   |   `- README.txt
  |   |- procfs/
  |   |   `- README.txt
  |   |- spiffs/
  |   |   `- README.md
  |   `- unionfs/
  |       `- README.txt
  |- graphics/
  |   `- README.txt
  |- libs/
  |   |- README.txt
  |   |- libc/
  |   |   |- zoneinfo
  |   |   |   `- README.txt
  |   |   `- README.txt
  |   |- libdsp/
  |   |   `- README.txt
  |   |- libnx/
  |   |   |- nxfongs
  |   |   |   `- README.txt
  |   |   `- README.txt
  |   |- libxx/
  |   `- README.txt
  |- mm/
  |   |- shm/
  |   |   `- README.txt
  |   `- README.txt
  |- net/
  |   |- sixlowpan
  |   |   `- README.txt
  |   `- README.txt
  |- pass1/
  |   `- README.txt
  |- syscall/
  |   `- README.txt
  `- tools/
      `- README.txt
 </pre></div>
 </div>
 <p>Below is a guide to the available README files in the semi-optional apps/
 source tree:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>apps/
  |- examples/
  |   |- bastest/README.txt
  |   |- json/README.txt
  |   |- pashello/README.txt
  |   `- README.txt
  |- gpsutils/
  |   `- minmea/README.txt
  |- graphics/
  |   |- tiff/README.txt
  |   `- traveler/tools/tcledit/README.txt
  |- interpreters/
  |   |- bas/
  |   |  `- README.txt
  |   |- ficl/
  |   |  `- README.txt
  |   `- README.txt
  |- modbus/
  |   `- README.txt
  |- netutils/
  |   |- discover/
  |   |  `- README.txt
  |   |- ftpc/
  |   |  `- README.txt
  |   |- json/
  |   |  `- README.txt
  |   |- telnetd/
  |   |  `- README.txt
  |   `- README.txt
  |- nshlib/
  |   `- README.txt
  |- NxWidgets/
  |   `- README.txt
  |- system/
  |   |- cdcacm/
  |   |  `- README.txt
  |   |- i2c/
  |   |  `- README.txt
  |   |- inifile/
  |   |  `- README.txt
  |   |- install/
  |   |  `- README.txt
  |   |- nsh/
  |   |  `- README.txt
  |   |- nxplayer/
  |   |  `- README.txt
  |   |- psmq/
  |   |  `- README.txt
  |   |- symtab/
  |   |   `- README.txt
  |   |- termcurses/
  |   |   `- README.txt
  |   |- usbmsc/
  |   |  `- README.txt
  |   `- zmodem/
  |      `- README.txt
  `- wireless
      |- bluetooth/
      |  `- btsak/
      |     `- README.txt
      `- ieee802154
         `- i8sak/
            `- README.txt
 </pre></div>
 </div>
 <p>Additional README.txt files in the other, related repositories:</p>
 <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>NxWidgets/
  |- Doxygen
  |   `- README.txt
  |- tools
  |   `- README.txt
  |- UnitTests
  |   `- README.txt
  `- README.txt

 buildroot/
  `- README.txt

 tools/
  `- README.txt

 uClibc++/
  `- README.txt
 </pre></div>
 </div>
 </section>
 </section>


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