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<li class="toctree-l2 current"><a class="reference internal" href="../index.html">Xtensa</a><ul class="current">
<li class="toctree-l3 current"><a class="current reference internal" href="#">Espressif ESP32</a><ul>
<li class="toctree-l4"><a class="reference internal" href="#esp32-toolchain">ESP32 Toolchain</a><ul>
<li class="toctree-l5"><a class="reference internal" href="#the-prebuilt-toolchain-recommended">The prebuilt Toolchain (Recommended)</a></li>
<li class="toctree-l5"><a class="reference internal" href="#building-from-source">Building from source</a></li>
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<li class="toctree-l4"><a class="reference internal" href="#building-and-flashing-nuttx">Building and flashing NuttX</a><ul>
<li class="toctree-l5"><a class="reference internal" href="#bootloader-and-partitions">Bootloader and partitions</a></li>
<li class="toctree-l5"><a class="reference internal" href="#building-and-flashing">Building and Flashing</a></li>
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<li class="toctree-l4"><a class="reference internal" href="#debugging">Debugging</a><ul>
<li class="toctree-l5"><a class="reference internal" href="#debugging-with-openocd-and-gdb">Debugging with <code class="docutils literal notranslate"><span class="pre">openocd</span></code> and <code class="docutils literal notranslate"><span class="pre">gdb</span></code></a></li>
<li class="toctree-l5"><a class="reference internal" href="#stack-dump-and-backtrace-dump">Stack Dump and Backtrace Dump</a></li>
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<li class="toctree-l4"><a class="reference internal" href="#peripheral-support">Peripheral Support</a></li>
<li class="toctree-l4"><a class="reference internal" href="#memory-map">Memory Map</a><ul>
<li class="toctree-l5"><a class="reference internal" href="#address-mapping">Address Mapping</a></li>
<li class="toctree-l5"><a class="reference internal" href="#embedded-memory">Embedded Memory</a></li>
<li class="toctree-l5"><a class="reference internal" href="#boundary-address-embedded">Boundary Address (Embedded)</a></li>
<li class="toctree-l5"><a class="reference internal" href="#external-memory">External Memory</a></li>
<li class="toctree-l5"><a class="reference internal" href="#boundary-address-external">Boundary Address (External)</a></li>
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<li class="toctree-l4"><a class="reference internal" href="#smp">SMP</a></li>
<li class="toctree-l4"><a class="reference internal" href="#wi-fi">Wi-Fi</a></li>
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<li class="toctree-l4"><a class="reference internal" href="#bluetooth">Bluetooth</a></li>
<li class="toctree-l4"><a class="reference internal" href="#i2s">I2S</a></li>
<li class="toctree-l4"><a class="reference internal" href="#using-qemu">Using QEMU</a><ul>
<li class="toctree-l5"><a class="reference internal" href="#qemu-networking">QEMU Networking</a></li>
</ul>
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<li class="toctree-l4"><a class="reference internal" href="#secure-boot-and-flash-encryption">Secure Boot and Flash Encryption</a><ul>
<li class="toctree-l5"><a class="reference internal" href="#secure-boot">Secure Boot</a></li>
<li class="toctree-l5"><a class="reference internal" href="#flash-encryption">Flash Encryption</a></li>
<li class="toctree-l5"><a class="reference internal" href="#prerequisites">Prerequisites</a></li>
<li class="toctree-l5"><a class="reference internal" href="#enabling-secure-boot-and-flash-encryption">Enabling Secure Boot and Flash Encryption</a></li>
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<li class="toctree-l4"><a class="reference internal" href="#things-to-do">Things to Do</a></li>
<li class="toctree-l4"><a class="reference internal" href="#supported-boards">Supported Boards</a><ul>
<li class="toctree-l5"><a class="reference internal" href="boards/esp32-2432S028/index.html">ESP32-2432S028</a></li>
<li class="toctree-l5"><a class="reference internal" href="boards/esp32-audio-kit/index.html">ESP32-AUDIO-KIT</a></li>
<li class="toctree-l5"><a class="reference internal" href="boards/esp32-devkitc/index.html">ESP32 DevKitC</a></li>
<li class="toctree-l5"><a class="reference internal" href="boards/esp32-ethernet-kit/index.html">ESP32-Ethernet-Kit V1.2</a></li>
<li class="toctree-l5"><a class="reference internal" href="boards/esp32-lyrat/index.html">ESP32-LyraT V4.3</a></li>
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<li class="toctree-l3"><a class="reference internal" href="../esp32s2/index.html">Espressif ESP32-S2</a></li>
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<section id="espressif-esp32">
<h1>Espressif ESP32<a class="headerlink" href="#espressif-esp32" title="Permalink to this heading"></a></h1>
<p>The ESP32 is a series of single and dual-core SoCs from Espressif
based on Harvard architecture Xtensa LX6 CPUs and with on-chip support
for Bluetooth and Wi-Fi.</p>
<p>All embedded memory, external memory and peripherals are located on the
data bus and/or the instruction bus of these CPUs. With some minor
exceptions, the address mapping of two CPUs is symmetric, meaning they
use the same addresses to access the same memory. Multiple peripherals in
the system can access embedded memory via DMA.</p>
<p>On dual-core SoCs, the two CPUs are typically named “PRO_CPU” and “APP_CPU”
(for “protocol” and “application”), however for most purposes the
two CPUs are interchangeable.</p>
<section id="esp32-toolchain">
<h2>ESP32 Toolchain<a class="headerlink" href="#esp32-toolchain" title="Permalink to this heading"></a></h2>
<p>The toolchain used to build ESP32 firmware can be either downloaded or built from the sources.
It is <strong>highly</strong> recommended to use (download or build) the same toolchain version that is being
used by the NuttX CI.</p>
<p>Please refer to the Docker
<a class="reference external" href="https://github.com/apache/nuttx/tree/master/tools/ci/docker/linux/Dockerfile">container</a> and
check for the current compiler version being used. For instance:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>###############################################################################
# Build image for tool required by ESP32 builds
###############################################################################
FROM nuttx-toolchain-base AS nuttx-toolchain-esp32
# Download the latest ESP32 GCC toolchain prebuilt by Espressif
RUN mkdir -p xtensa-esp32-elf-gcc &amp;&amp; \
curl -s -L &quot;https://github.com/espressif/crosstool-NG/releases/download/esp-12.2.0_20230208/xtensa-esp32-elf-12.2.0_20230208-x86_64-linux-gnu.tar.xz&quot; \
| tar -C xtensa-esp32-elf-gcc --strip-components 1 -xJ
RUN mkdir -p xtensa-esp32s2-elf-gcc &amp;&amp; \
curl -s -L &quot;https://github.com/espressif/crosstool-NG/releases/download/esp-12.2.0_20230208/xtensa-esp32s2-elf-12.2.0_20230208-x86_64-linux-gnu.tar.xz&quot; \
| tar -C xtensa-esp32s2-elf-gcc --strip-components 1 -xJ
RUN mkdir -p xtensa-esp32s3-elf-gcc &amp;&amp; \
curl -s -L &quot;https://github.com/espressif/crosstool-NG/releases/download/esp-12.2.0_20230208/xtensa-esp32s3-elf-12.2.0_20230208-x86_64-linux-gnu.tar.xz&quot; \
| tar -C xtensa-esp32s3-elf-gcc --strip-components 1 -xJ
</pre></div>
</div>
<p>For ESP32, the toolchain version is based on GGC 12.2.0 (<code class="docutils literal notranslate"><span class="pre">xtensa-esp32-elf-12.2.0_20230208</span></code>)</p>
<section id="the-prebuilt-toolchain-recommended">
<h3>The prebuilt Toolchain (Recommended)<a class="headerlink" href="#the-prebuilt-toolchain-recommended" title="Permalink to this heading"></a></h3>
<p>First, create a directory to hold the toolchain:</p>
<div class="highlight-console notranslate"><div class="highlight"><pre><span></span><span class="gp">$ </span>mkdir<span class="w"> </span>-p<span class="w"> </span>/path/to/your/toolchain/xtensa-esp32-elf-gcc
</pre></div>
</div>
<p>Download and extract toolchain:</p>
<div class="highlight-console notranslate"><div class="highlight"><pre><span></span><span class="gp">$ </span>curl<span class="w"> </span>-s<span class="w"> </span>-L<span class="w"> </span><span class="s2">&quot;https://github.com/espressif/crosstool-NG/releases/download/esp-12.2.0_20230208/xtensa-esp32-elf-12.2.0_20230208-x86_64-linux-gnu.tar.xz&quot;</span><span class="w"> </span><span class="se">\</span>
<span class="p">|</span><span class="w"> </span>tar<span class="w"> </span>-C<span class="w"> </span>xtensa-esp32-elf-gcc<span class="w"> </span>--strip-components<span class="w"> </span><span class="m">1</span><span class="w"> </span>-xJ
</pre></div>
</div>
<p>Add the toolchain to your <cite>PATH</cite>:</p>
<div class="highlight-console notranslate"><div class="highlight"><pre><span></span><span class="gp">$ </span><span class="nb">echo</span><span class="w"> </span><span class="s2">&quot;export PATH=/path/to/your/toolchain/xtensa-esp32-elf-gcc/bin:</span><span class="nv">$PATH</span><span class="s2">&quot;</span><span class="w"> </span>&gt;&gt;<span class="w"> </span>~/.bashrc
</pre></div>
</div>
<p>You can edit your shell’s rc files if you don’t use bash.</p>
</section>
<section id="building-from-source">
<h3>Building from source<a class="headerlink" href="#building-from-source" title="Permalink to this heading"></a></h3>
<p>You can also build the toolchain yourself. The steps to
build the toolchain with crosstool-NG on Linux are as follows</p>
<div class="highlight-console notranslate"><div class="highlight"><pre><span></span><span class="gp">$ </span>git<span class="w"> </span>clone<span class="w"> </span>https://github.com/espressif/crosstool-NG.git
<span class="gp">$ </span><span class="nb">cd</span><span class="w"> </span>crosstool-NG
<span class="gp">$ </span>git<span class="w"> </span>submodule<span class="w"> </span>update<span class="w"> </span>--init
<span class="gp">$ </span>./bootstrap<span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span>./configure<span class="w"> </span>--enable-local<span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span>make
<span class="gp">$ </span>./ct-ng<span class="w"> </span>xtensa-esp32-elf
<span class="gp">$ </span>./ct-ng<span class="w"> </span>build
<span class="gp">$ </span>chmod<span class="w"> </span>-R<span class="w"> </span>u+w<span class="w"> </span>builds/xtensa-esp32-elf
<span class="gp">$ </span><span class="nb">export</span><span class="w"> </span><span class="nv">PATH</span><span class="o">=</span><span class="s2">&quot;crosstool-NG/builds/xtensa-esp32-elf/bin:</span><span class="nv">$PATH</span><span class="s2">&quot;</span>
</pre></div>
</div>
<p>These steps are given in the setup guide in
<a class="reference external" href="https://docs.espressif.com/projects/esp-idf/en/latest/get-started/linux-setup-scratch.html">ESP-IDF documentation</a>.</p>
</section>
</section>
<section id="building-and-flashing-nuttx">
<h2>Building and flashing NuttX<a class="headerlink" href="#building-and-flashing-nuttx" title="Permalink to this heading"></a></h2>
<section id="bootloader-and-partitions">
<h3>Bootloader and partitions<a class="headerlink" href="#bootloader-and-partitions" title="Permalink to this heading"></a></h3>
<p>NuttX can boot the ESP32 directly using the so-called “Simple Boot”. An externally-built
2nd stage bootloader is not required in this case as all functions required to boot the device
are built within NuttX. Simple boot does not require any specific configuration (it is selectable
by default if no other 2nd stage bootloader is used).</p>
<p>If other features are required, an externally-built 2nd stage bootloader is needed. The bootloader
is built using the <code class="docutils literal notranslate"><span class="pre">make</span> <span class="pre">bootloader</span></code> command. This command generates the firmware in the
<code class="docutils literal notranslate"><span class="pre">nuttx</span></code> folder. The <code class="docutils literal notranslate"><span class="pre">ESPTOOL_BINDIR</span></code> is used in the <code class="docutils literal notranslate"><span class="pre">make</span> <span class="pre">flash</span></code> command to specify the path
to the bootloader. For compatibility among other SoCs and future options of 2nd stage bootloaders,
the commands <code class="docutils literal notranslate"><span class="pre">make</span> <span class="pre">bootloader</span></code> and the <code class="docutils literal notranslate"><span class="pre">ESPTOOL_BINDIR</span></code> option (for the <code class="docutils literal notranslate"><span class="pre">make</span> <span class="pre">flash</span></code>) can be
used even if no externally-built 2nd stage bootloader is being built (they will be ignored if
Simple Boot is used, for instance):</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>$ make bootloader
</pre></div>
</div>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>It is recommended that if this is the first time you are using the board with NuttX to
perform a complete SPI FLASH erase.</p>
<blockquote>
<div><div class="highlight-console notranslate"><div class="highlight"><pre><span></span><span class="gp">$ </span>esptool.py<span class="w"> </span>erase_flash
</pre></div>
</div>
</div></blockquote>
</div>
</section>
<section id="building-and-flashing">
<h3>Building and Flashing<a class="headerlink" href="#building-and-flashing" title="Permalink to this heading"></a></h3>
<p>First, make sure that <code class="docutils literal notranslate"><span class="pre">esptool.py</span></code> is installed. This tool is used to convert the ELF to a
compatible ESP32 image and to flash the image into the board.
It can be installed with: <code class="docutils literal notranslate"><span class="pre">pip</span> <span class="pre">install</span> <span class="pre">esptool==4.8.dev4</span></code>.</p>
<p>It’s a two-step process where the first converts the ELF file into an ESP32 compatible binary
and the second flashes it to the board. These steps are included in the build system and it is
possible to build and flash the NuttX firmware simply by running:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>$ make flash ESPTOOL_PORT=&lt;port&gt; ESPTOOL_BINDIR=./
</pre></div>
</div>
<p>where <code class="docutils literal notranslate"><span class="pre">&lt;port&gt;</span></code> is typically <code class="docutils literal notranslate"><span class="pre">/dev/ttyUSB0</span></code> or similar. <code class="docutils literal notranslate"><span class="pre">ESPTOOL_BINDIR=./</span></code> is the path of the
externally-built 2nd stage bootloader and the partition table (if applicable): when built using the
<code class="docutils literal notranslate"><span class="pre">make</span> <span class="pre">bootloader</span></code>, these files are placed into <code class="docutils literal notranslate"><span class="pre">nuttx</span></code> folder. <code class="docutils literal notranslate"><span class="pre">ESPTOOL_BAUD</span></code> is able to
change the flash baud rate if desired.</p>
</section>
</section>
<section id="debugging">
<h2>Debugging<a class="headerlink" href="#debugging" title="Permalink to this heading"></a></h2>
<p>This section describes debugging techniques for the ESP32.</p>
<section id="debugging-with-openocd-and-gdb">
<h3>Debugging with <code class="docutils literal notranslate"><span class="pre">openocd</span></code> and <code class="docutils literal notranslate"><span class="pre">gdb</span></code><a class="headerlink" href="#debugging-with-openocd-and-gdb" title="Permalink to this heading"></a></h3>
<p>Espressif uses a specific version of OpenOCD to support ESP32: <a class="reference external" href="https://github.com/espressif/">openocd-esp32</a>.</p>
<p>Please check <a class="reference external" href="https://docs.espressif.com/projects/esp-idf/en/release-v5.1/esp32/api-guides/jtag-debugging/index.html#jtag-debugging-building-openocd">Building OpenOCD from Sources</a>
for more information on how to build OpenOCD for ESP32.</p>
<p>ESP32 has dedicated pins for JTAG debugging. The following pins are used for JTAG debugging:</p>
<table class="docutils align-default">
<thead>
<tr class="row-odd"><th class="head"><p>ESP32 Pin</p></th>
<th class="head"><p>JTAG Signal</p></th>
</tr>
</thead>
<tbody>
<tr class="row-even"><td><p>MTDO / GPIO15</p></td>
<td><p>TDO</p></td>
</tr>
<tr class="row-odd"><td><p>MTDI / GPIO12</p></td>
<td><p>TDI</p></td>
</tr>
<tr class="row-even"><td><p>MTCK / GPIO13</p></td>
<td><p>TCK</p></td>
</tr>
<tr class="row-odd"><td><p>MTMS / GPIO14</p></td>
<td><p>TMS</p></td>
</tr>
</tbody>
</table>
<p>Some boards, like <a class="reference internal" href="boards/esp32-ethernet-kit/index.html#esp32-ethernet-kit-v1-2"><span class="std std-ref">ESP32-Ethernet-Kit V1.2</span></a> and
<a class="reference internal" href="boards/esp32-wrover-kit/index.html#esp-wrover-kit"><span class="std std-ref">ESP-WROVER-KIT</span></a>, have a built-in JTAG debugger.</p>
<p>Other boards that don’t have any built-in JTAG debugger can be debugged using an external JTAG debugger, like the one
described for the <a class="reference internal" href="boards/esp32-devkitc/index.html#debugging-with-openocd"><span class="std std-ref">ESP32-DevKitC</span></a>.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>One must configure the USB drivers to enable JTAG communication. Please check
<a class="reference external" href="https://docs.espressif.com/projects/esp-idf/en/release-v5.1/esp32/api-guides/jtag-debugging/configure-ft2232h-jtag.html#configure-usb-drivers">Configure USB Drivers</a>
for configuring the JTAG adapter of the <a class="reference internal" href="boards/esp32-ethernet-kit/index.html#esp32-ethernet-kit-v1-2"><span class="std std-ref">ESP32-Ethernet-Kit V1.2</span></a> and
<a class="reference internal" href="boards/esp32-wrover-kit/index.html#esp-wrover-kit"><span class="std std-ref">ESP-WROVER-KIT</span></a> boards and other FT2232-based JTAG adapters.</p>
</div>
<p>OpenOCD can then be used:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>openocd -c &#39;set ESP_RTOS hwthread; set ESP_FLASH_SIZE 0&#39; -f board/esp32-wrover-kit-1.8v.cfg
</pre></div>
</div>
<p>Once OpenOCD is running, you can use GDB to connect to it and debug your application:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>xtensa-esp32-elf-gdb -x gdbinit nuttx
</pre></div>
</div>
<p>whereas the content of the <code class="docutils literal notranslate"><span class="pre">gdbinit</span></code> file is:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>target remote :3333
set remote hardware-watchpoint-limit 2
mon reset halt
flushregs
monitor reset halt
thb nsh_main
c
</pre></div>
</div>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p><code class="docutils literal notranslate"><span class="pre">nuttx</span></code> is the ELF file generated by the build process. Please note that <code class="docutils literal notranslate"><span class="pre">CONFIG_DEBUG_SYMBOLS</span></code> must be enabled in the <code class="docutils literal notranslate"><span class="pre">menuconfig</span></code>.</p>
</div>
<p>Please refer to <a class="reference internal" href="../../../quickstart/debugging.html"><span class="doc">Debugging</span></a> for more information about debugging techniques.</p>
</section>
<section id="stack-dump-and-backtrace-dump">
<h3>Stack Dump and Backtrace Dump<a class="headerlink" href="#stack-dump-and-backtrace-dump" title="Permalink to this heading"></a></h3>
<p>NuttX has a feature to dump the stack of a task and to dump the backtrace of it (and of all
the other tasks). This feature is useful to debug the system when it is not behaving as expected,
especially when it is crashing.</p>
<p>In order to enable this feature, the following options must be enabled in the NuttX configuration:
<code class="docutils literal notranslate"><span class="pre">CONFIG_SCHED_BACKTRACE</span></code>, <code class="docutils literal notranslate"><span class="pre">CONFIG_DEBUG_SYMBOLS</span></code> and, optionally, <code class="docutils literal notranslate"><span class="pre">CONFIG_ALLSYMS</span></code>.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>The first two options enable the backtrace dump. The third option enables the backtrace dump
with the associated symbols, but increases the size of the generated NuttX binary.</p>
</div>
<p>Espressif also provides a tool to translate the backtrace dump into a human-readable format.
This tool is called <code class="docutils literal notranslate"><span class="pre">btdecode.sh</span></code> and is available at <code class="docutils literal notranslate"><span class="pre">tools/espressif/btdecode.sh</span></code> of NuttX
repository.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>This tool is not necessary if <code class="docutils literal notranslate"><span class="pre">CONFIG_ALLSYMS</span></code> is enabled. In this case, the backtrace dump
contains the function names.</p>
</div>
<section id="example-crash-dump">
<h4>Example - Crash Dump<a class="headerlink" href="#example-crash-dump" title="Permalink to this heading"></a></h4>
<p>A typical crash dump, caused by an illegal load with <code class="docutils literal notranslate"><span class="pre">CONFIG_SCHED_BACKTRACE</span></code> and
<code class="docutils literal notranslate"><span class="pre">CONFIG_DEBUG_SYMBOLS</span></code> enabled, is shown below:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>xtensa_user_panic: User Exception: EXCCAUSE=001d task: backtrace
_assert: Current Version: NuttX 10.4.0 2ae3246e40-dirty Sep 19 2024 12:59:10 xtensa
_assert: Assertion failed user panic: at file: :0 task: backtrace process: backtrace 0x400f0724
up_dump_register: PC: 400f0754 PS: 00060530
up_dump_register: A0: 800e2fcc A1: 3ffe1400 A2: 00000000 A3: 3ffe0470
up_dump_register: A4: 3ffe0486 A5: 3ffaf4b0 A6: 00000000 A7: 00000000
up_dump_register: A8: 800f0751 A9: 3ffe13d0 A10: 0000005a A11: 3ffafcb0
up_dump_register: A12: 00000059 A13: 3ffaf600 A14: 00000002 A15: 3ffafaa4
up_dump_register: SAR: 00000018 CAUSE: 0000001d VADDR: 00000000
up_dump_register: LBEG: 4000c28c LEND: 4000c296 LCNT: 00000000
dump_stack: User Stack:
dump_stack: base: 0x3ffe0490
dump_stack: size: 00004048
dump_stack: sp: 0x3ffe1400
stack_dump: 0x3ffe13e0: 00000059 3ffaf600 00000002 3ffafaa4 800e1eb4 3ffe1420 400f0724 00000002
stack_dump: 0x3ffe1400: 3ffe0486 3ffaf4b0 00000000 00000000 00000000 3ffe1440 00000000 400f0724
stack_dump: 0x3ffe1420: 3ffe0470 3ffafae8 00000000 3ffb0d2c 00000000 3ffe1460 00000000 00000000
stack_dump: 0x3ffe1440: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
stack_dump: 0x3ffe1460: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
sched_dumpstack: backtrace| 2: 0x400ef738 0x40085152 0x40084d05 0x40084c7d 0x40080c84 0x400f0754 0x400e2fcc 0x400e1eb4
sched_dumpstack: backtrace| 2: 0x40000000 0x400e2fcc 0x400e1eb4 0x40000000
dump_tasks: PID GROUP PRI POLICY TYPE NPX STATE EVENT SIGMASK STACKBASE STACKSIZE COMMAND
dump_task: 0 0 0 FIFO Kthread - Ready 0000000000000000 0x3ffb0010 3056 Idle_Task
dump_task: 1 1 100 RR Task - Waiting Semaphore 0000000000000000 0x3ffaec10 3024 nsh_main
dump_task: 2 2 255 RR Task - Running 0000000000000000 0x3ffe0490 4048 backtrace task
sched_dumpstack: backtrace| 0: 0x400e12bb 0x400826eb
sched_dumpstack: backtrace| 1: 0x400edc59 0x400edb5b 0x400edb94 0x400e6c36 0x400e643c 0x400e6714 0x400e5830 0x400e56b8
sched_dumpstack: backtrace| 1: 0x400e5689 0x400e2fcc 0x400e1eb4 0x40000000
sched_dumpstack: backtrace| 2: 0x400ef738 0x40084ed4 0x400ed9ea 0x40085184 0x40084d05 0x40084c7d 0x40080c84 0x400f0754
sched_dumpstack: backtrace| 2: 0x400e2fcc 0x400e1eb4 0x40000000 0x400e2fcc 0x400e1eb4 0x40000000
</pre></div>
</div>
<p>The lines starting with <code class="docutils literal notranslate"><span class="pre">sched_dumpstack</span></code> show the backtrace of the tasks. By checking it, it is
possible to track the root cause of the crash. Saving this output to a file and using the <code class="docutils literal notranslate"><span class="pre">btdecode.sh</span></code>:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>./tools/btdecode.sh esp32 /tmp/backtrace.txt
Backtrace for task 2:
0x400ef738: sched_dumpstack at sched_dumpstack.c:69
0x40085152: _assert at assert.c:691
0x40084d05: xtensa_user_panic at xtensa_assert.c:188 (discriminator 1)
0x40084c7d: xtensa_user at ??:?
0x40080c84: _xtensa_user_handler at xtensa_user_handler.S:194
0x400f0754: assert_on_task at backtrace_main.c:158
(inlined by) backtrace_main at backtrace_main.c:194
0x400e2fcc: nxtask_startup at task_startup.c:70
0x400e1eb4: nxtask_start at task_start.c:75
0x40000000: ?? ??:0
0x400e2fcc: nxtask_startup at task_startup.c:70
0x400e1eb4: nxtask_start at task_start.c:75
0x40000000: ?? ??:0
Backtrace dump for all tasks:
Backtrace for task 2:
0x400ef738: sched_dumpstack at sched_dumpstack.c:69
0x40084ed4: dump_backtrace at assert.c:418
0x400ed9ea: nxsched_foreach at sched_foreach.c:69 (discriminator 2)
0x40085184: _assert at assert.c:726
0x40084d05: xtensa_user_panic at xtensa_assert.c:188 (discriminator 1)
0x40084c7d: xtensa_user at ??:?
0x40080c84: _xtensa_user_handler at xtensa_user_handler.S:194
0x400f0754: assert_on_task at backtrace_main.c:158
(inlined by) backtrace_main at backtrace_main.c:194
0x400e2fcc: nxtask_startup at task_startup.c:70
0x400e1eb4: nxtask_start at task_start.c:75
0x40000000: ?? ??:0
0x400e2fcc: nxtask_startup at task_startup.c:70
0x400e1eb4: nxtask_start at task_start.c:75
0x40000000: ?? ??:0
Backtrace for task 1:
0x400edc59: nxsem_wait at sem_wait.c:217
0x400edb5b: nxsched_waitpid at sched_waitpid.c:165
0x400edb94: waitpid at sched_waitpid.c:618
0x400e6c36: nsh_builtin at nsh_builtin.c:163
0x400e643c: nsh_execute at nsh_parse.c:652
(inlined by) nsh_parse_command at nsh_parse.c:2840
0x400e6714: nsh_parse at nsh_parse.c:2930
0x400e5830: nsh_session at nsh_session.c:246
0x400e56b8: nsh_consolemain at nsh_consolemain.c:79
0x400e5689: nsh_main at nsh_main.c:80
0x400e2fcc: nxtask_startup at task_startup.c:70
0x400e1eb4: nxtask_start at task_start.c:75
0x40000000: ?? ??:0
Backtrace for task 0:
0x400e12bb: nx_start at nx_start.c:772 (discriminator 1)
0x400826eb: __esp32_start at esp32_start.c:294
(inlined by) __start at esp32_start.c:358
</pre></div>
</div>
<p>The above output shows the backtrace of the tasks. By checking it, it is possible to track the
functions that were being executed when the crash occurred.</p>
</section>
</section>
</section>
<section id="peripheral-support">
<h2>Peripheral Support<a class="headerlink" href="#peripheral-support" title="Permalink to this heading"></a></h2>
<p>The following list indicates the state of peripherals’ support in NuttX:</p>
<table class="docutils align-default">
<thead>
<tr class="row-odd"><th class="head"><p>Peripheral</p></th>
<th class="head"><p>Support</p></th>
<th class="head"><p>NOTES</p></th>
</tr>
</thead>
<tbody>
<tr class="row-even"><td><p>ADC</p></td>
<td><p>No</p></td>
<td></td>
</tr>
<tr class="row-odd"><td><p>AES</p></td>
<td><p>Yes</p></td>
<td></td>
</tr>
<tr class="row-even"><td><p>Bluetooth</p></td>
<td><p>Yes</p></td>
<td></td>
</tr>
<tr class="row-odd"><td><p>CAN/TWAI</p></td>
<td><p>Yes</p></td>
<td></td>
</tr>
<tr class="row-even"><td><p>DMA</p></td>
<td><p>Yes</p></td>
<td></td>
</tr>
<tr class="row-odd"><td><p>DAC</p></td>
<td><p>Yes</p></td>
<td><p>One-shot</p></td>
</tr>
<tr class="row-even"><td><p>eFuse</p></td>
<td><p>Yes</p></td>
<td></td>
</tr>
<tr class="row-odd"><td><p>Ethernet</p></td>
<td><p>Yes</p></td>
<td></td>
</tr>
<tr class="row-even"><td><p>GPIO</p></td>
<td><p>Yes</p></td>
<td></td>
</tr>
<tr class="row-odd"><td><p>I2C</p></td>
<td><p>Yes</p></td>
<td><p>Master and Slave mode supported</p></td>
</tr>
<tr class="row-even"><td><p>I2S</p></td>
<td><p>Yes</p></td>
<td></td>
</tr>
<tr class="row-odd"><td><p>LED_PWM</p></td>
<td><p>Yes</p></td>
<td></td>
</tr>
<tr class="row-even"><td><p>MCPWM</p></td>
<td><p>Yes</p></td>
<td></td>
</tr>
<tr class="row-odd"><td><p>Pulse_CNT</p></td>
<td><p>Yes</p></td>
<td></td>
</tr>
<tr class="row-even"><td><p>RMT</p></td>
<td><p>Yes</p></td>
<td></td>
</tr>
<tr class="row-odd"><td><p>RNG</p></td>
<td><p>Yes</p></td>
<td></td>
</tr>
<tr class="row-even"><td><p>RSA</p></td>
<td><p>No</p></td>
<td></td>
</tr>
<tr class="row-odd"><td><p>RTC</p></td>
<td><p>Yes</p></td>
<td></td>
</tr>
<tr class="row-even"><td><p>SD/MMC</p></td>
<td><p>No</p></td>
<td></td>
</tr>
<tr class="row-odd"><td><p>SDIO</p></td>
<td><p>No</p></td>
<td></td>
</tr>
<tr class="row-even"><td><p>SHA</p></td>
<td><p>No</p></td>
<td></td>
</tr>
<tr class="row-odd"><td><p>SPI</p></td>
<td><p>Yes</p></td>
<td></td>
</tr>
<tr class="row-even"><td><p>SPIFLASH</p></td>
<td><p>Yes</p></td>
<td></td>
</tr>
<tr class="row-odd"><td><p>SPIRAM</p></td>
<td><p>Yes</p></td>
<td></td>
</tr>
<tr class="row-even"><td><p>Timers</p></td>
<td><p>Yes</p></td>
<td></td>
</tr>
<tr class="row-odd"><td><p>Touch</p></td>
<td><p>Yes</p></td>
<td></td>
</tr>
<tr class="row-even"><td><p>UART</p></td>
<td><p>Yes</p></td>
<td></td>
</tr>
<tr class="row-odd"><td><p>Watchdog</p></td>
<td><p>Yes</p></td>
<td></td>
</tr>
<tr class="row-even"><td><p>Wifi</p></td>
<td><p>Yes</p></td>
<td></td>
</tr>
</tbody>
</table>
</section>
<section id="memory-map">
<h2>Memory Map<a class="headerlink" href="#memory-map" title="Permalink to this heading"></a></h2>
<section id="address-mapping">
<h3>Address Mapping<a class="headerlink" href="#address-mapping" title="Permalink to this heading"></a></h3>
<table class="docutils align-default">
<thead>
<tr class="row-odd"><th class="head"><p>BUS TYPE</p></th>
<th class="head"><p>START</p></th>
<th class="head"><p>LAST</p></th>
<th class="head"><p>DESCRIPTION</p></th>
<th class="head"><p>NOTES</p></th>
</tr>
</thead>
<tbody>
<tr class="row-even"><td><p>Data</p></td>
<td><p>0x3F400000</p></td>
<td><p>0x3F7FFFFF</p></td>
<td><p>External Memory</p></td>
<td></td>
</tr>
<tr class="row-odd"><td><p>Data</p></td>
<td><p>0x3F800000
0x3FC00000</p></td>
<td><p>0x3FBFFFFF
0x3FEFFFFF</p></td>
<td><p>External Memory</p></td>
<td><p>Reserved</p></td>
</tr>
<tr class="row-even"><td><p>Data</p></td>
<td><p>0x3FF00000</p></td>
<td><p>0x3FF7FFFF</p></td>
<td><p>Peripheral</p></td>
<td></td>
</tr>
<tr class="row-odd"><td><p>Data</p></td>
<td><p>0x3FF80000</p></td>
<td><p>0x3FFFFFFF</p></td>
<td><p>Embedded Memory</p></td>
<td></td>
</tr>
<tr class="row-even"><td><p>Instruction</p></td>
<td><p>0x40000000</p></td>
<td><p>0x400C1FFF</p></td>
<td><p>Embedded Memory</p></td>
<td></td>
</tr>
<tr class="row-odd"><td><p>Instruction</p></td>
<td><p>0x400C2000</p></td>
<td><p>0x40BFFFFF</p></td>
<td><p>External Memory</p></td>
<td></td>
</tr>
<tr class="row-even"><td><p>.</p></td>
<td><p>0x40C00000</p></td>
<td><p>0x4FFFFFFF</p></td>
<td></td>
<td><p>Reserved</p></td>
</tr>
<tr class="row-odd"><td><p>Data / Instruction</p></td>
<td><p>0x50000000</p></td>
<td><p>0x50001FFF</p></td>
<td><p>Embedded Memory</p></td>
<td></td>
</tr>
<tr class="row-even"><td><p>.</p></td>
<td><p>0x50002000</p></td>
<td><p>0xFFFFFFFF</p></td>
<td></td>
<td><p>Reserved</p></td>
</tr>
</tbody>
</table>
</section>
<section id="embedded-memory">
<h3>Embedded Memory<a class="headerlink" href="#embedded-memory" title="Permalink to this heading"></a></h3>
<table class="docutils align-default">
<thead>
<tr class="row-odd"><th class="head"><p>BUS TYPE</p></th>
<th class="head"><p>START</p></th>
<th class="head"><p>LAST</p></th>
<th class="head"><p>DESCRIPTION</p></th>
<th class="head"><p>NOTES</p></th>
</tr>
</thead>
<tbody>
<tr class="row-even"><td><p>Data</p></td>
<td><p>0x3ff80000</p></td>
<td><p>0x3ff81fff</p></td>
<td><p>RTC FAST Memory</p></td>
<td><p>PRO_CPU Only</p></td>
</tr>
<tr class="row-odd"><td><p>.</p></td>
<td><p>0x3ff82000</p></td>
<td><p>0x3ff8ffff</p></td>
<td></td>
<td><p>Reserved</p></td>
</tr>
<tr class="row-even"><td><p>Data</p></td>
<td><p>0x3ff90000</p></td>
<td><p>0x3ff9ffff</p></td>
<td><p>Internal ROM 1</p></td>
<td></td>
</tr>
<tr class="row-odd"><td><p>.</p></td>
<td><p>0x3ffa0000</p></td>
<td><p>0x3ffadfff</p></td>
<td></td>
<td><p>Reserved</p></td>
</tr>
<tr class="row-even"><td><p>Data</p></td>
<td><p>0x3ffae000</p></td>
<td><p>0x3ffdffff</p></td>
<td><p>Internal SRAM 2</p></td>
<td><p>DMA</p></td>
</tr>
<tr class="row-odd"><td><p>Data</p></td>
<td><p>0x3ffe0000</p></td>
<td><p>0x3fffffff</p></td>
<td><p>Internal SRAM 1</p></td>
<td><p>DMA</p></td>
</tr>
</tbody>
</table>
</section>
<section id="boundary-address-embedded">
<h3>Boundary Address (Embedded)<a class="headerlink" href="#boundary-address-embedded" title="Permalink to this heading"></a></h3>
<table class="docutils align-default">
<thead>
<tr class="row-odd"><th class="head"><p>BUS TYPE</p></th>
<th class="head"><p>START</p></th>
<th class="head"><p>LAST</p></th>
<th class="head"><p>DESCRIPTION</p></th>
<th class="head"><p>NOTES</p></th>
</tr>
</thead>
<tbody>
<tr class="row-even"><td><p>Instruction</p></td>
<td><p>0x40000000</p></td>
<td><p>0x40007fff</p></td>
<td><p>Internal ROM 0</p></td>
<td><p>Remap</p></td>
</tr>
<tr class="row-odd"><td><p>Instruction</p></td>
<td><p>0x40008000</p></td>
<td><p>0x4005ffff</p></td>
<td><p>Internal ROM 0</p></td>
<td></td>
</tr>
<tr class="row-even"><td><p>.</p></td>
<td><p>0x40060000</p></td>
<td><p>0x4006ffff</p></td>
<td></td>
<td><p>Reserved</p></td>
</tr>
<tr class="row-odd"><td><p>Instruction</p></td>
<td><p>0x40070000</p></td>
<td><p>0x4007ffff</p></td>
<td><p>Internal SRAM 0</p></td>
<td><p>Cache</p></td>
</tr>
<tr class="row-even"><td><p>Instruction</p></td>
<td><p>0x40080000</p></td>
<td><p>0x4009ffff</p></td>
<td><p>Internal SRAM 0</p></td>
<td></td>
</tr>
<tr class="row-odd"><td><p>Instruction</p></td>
<td><p>0x400a0000</p></td>
<td><p>0x400affff</p></td>
<td><p>Internal SRAM 1</p></td>
<td></td>
</tr>
<tr class="row-even"><td><p>Instruction</p></td>
<td><p>0x400b0000</p></td>
<td><p>0x400b7FFF</p></td>
<td><p>Internal SRAM 1</p></td>
<td><p>Remap</p></td>
</tr>
<tr class="row-odd"><td><p>Instruction</p></td>
<td><p>0x400b8000</p></td>
<td><p>0x400bffff</p></td>
<td><p>Internal SRAM 1</p></td>
<td></td>
</tr>
<tr class="row-even"><td><p>Instruction</p></td>
<td><p>0x400c0000</p></td>
<td><p>0x400c1FFF</p></td>
<td><p>RTC FAST Memory</p></td>
<td><p>PRO_CPU Only</p></td>
</tr>
<tr class="row-odd"><td><p>Data / Instruction</p></td>
<td><p>0x50000000</p></td>
<td><p>0x50001fff</p></td>
<td><p>RTC SLOW Memory</p></td>
<td></td>
</tr>
</tbody>
</table>
</section>
<section id="external-memory">
<h3>External Memory<a class="headerlink" href="#external-memory" title="Permalink to this heading"></a></h3>
<table class="docutils align-default">
<thead>
<tr class="row-odd"><th class="head"><p>BUS TYPE</p></th>
<th class="head"><p>START</p></th>
<th class="head"><p>LAST</p></th>
<th class="head"><p>DESCRIPTION</p></th>
<th class="head"><p>NOTES</p></th>
</tr>
</thead>
<tbody>
<tr class="row-even"><td><p>Data</p></td>
<td><p>0x3f400000</p></td>
<td><p>0x3f7fffff</p></td>
<td><p>External Flash</p></td>
<td><p>Read</p></td>
</tr>
<tr class="row-odd"><td><p>Data</p></td>
<td><p>0x3f800000</p></td>
<td><p>0x3fbfffff</p></td>
<td><p>External SRAM</p></td>
<td><p>Read and Write</p></td>
</tr>
</tbody>
</table>
</section>
<section id="boundary-address-external">
<h3>Boundary Address (External)<a class="headerlink" href="#boundary-address-external" title="Permalink to this heading"></a></h3>
<p>Instruction 0x400c2000 0x40bfffff 11512 KB External Flash Read</p>
</section>
<section id="linker-segments">
<h3>Linker Segments<a class="headerlink" href="#linker-segments" title="Permalink to this heading"></a></h3>
<table class="docutils align-default">
<thead>
<tr class="row-odd"><th class="head"><p>DESCRIPTION</p></th>
<th class="head"><p>START</p></th>
<th class="head"><p>END</p></th>
<th class="head"><p>ATTR</p></th>
<th class="head"><p>LINKER SEGMENT NAME</p></th>
</tr>
</thead>
<tbody>
<tr class="row-even"><td><dl class="simple">
<dt>FLASH mapped data:</dt><dd><ul class="simple">
<li><p>.rodata</p></li>
<li><p>Constructors
/destructors</p></li>
</ul>
</dd>
</dl>
</td>
<td><p>0x3f400010</p></td>
<td><p>0x3fc00010</p></td>
<td><p>R</p></td>
<td><p>drom0_0_seg</p></td>
</tr>
<tr class="row-odd"><td><dl class="simple">
<dt>COMMON data RAM:</dt><dd><ul class="simple">
<li><p>.bss/.data</p></li>
</ul>
</dd>
</dl>
</td>
<td><p>0x3ffb0000</p></td>
<td><p>0x40000000</p></td>
<td><p>RW</p></td>
<td><p>dram0_0_seg (NOTE 1,2,3)</p></td>
</tr>
<tr class="row-even"><td><dl class="simple">
<dt>IRAM for PRO cpu:</dt><dd><ul class="simple">
<li><p>Interrupt Vectors</p></li>
<li><p>Low level
handlers</p></li>
<li><p>Xtensa/Espressif
libraries</p></li>
</ul>
</dd>
</dl>
</td>
<td><p>0x40080000</p></td>
<td><p>0x400a0000</p></td>
<td><p>RX</p></td>
<td><p>iram0_0_seg</p></td>
</tr>
<tr class="row-odd"><td><dl class="simple">
<dt>RTC fast memory:</dt><dd><ul class="simple">
<li><p>.rtc.text
(unused?)</p></li>
</ul>
</dd>
</dl>
</td>
<td><p>0x400c0000</p></td>
<td><p>0x400c2000</p></td>
<td><p>RWX</p></td>
<td><p>rtc_iram_seg (PRO_CPU only)</p></td>
</tr>
<tr class="row-even"><td><dl class="simple">
<dt>FLASH:</dt><dd><ul class="simple">
<li><p>.text</p></li>
</ul>
</dd>
</dl>
</td>
<td><p>0x400d0018</p></td>
<td><p>0x40400018</p></td>
<td><p>RX</p></td>
<td><p>iram0_2_seg (actually FLASH)</p></td>
</tr>
<tr class="row-odd"><td><dl class="simple">
<dt>RTC slow memory:</dt><dd><ul class="simple">
<li><p>.rtc.data/rodata
(unused?)</p></li>
</ul>
</dd>
</dl>
</td>
<td><p>0x50000000</p></td>
<td><p>0x50001000</p></td>
<td><p>RW</p></td>
<td><p>rtc_slow_seg (NOTE 4)</p></td>
</tr>
</tbody>
</table>
<div class="admonition note">
<p class="admonition-title">Note</p>
<ol class="arabic simple">
<li><p>Linker script will reserve space at the beginning of the segment
for BT and at the end for trace memory.</p></li>
<li><p>Heap ends at the top of dram_0_seg.</p></li>
<li><p>Parts of this region is reserved for the ROM bootloader.</p></li>
<li><p>Linker script will reserve space at the beginning of the segment
for co-processor reserve memory and at the end for ULP coprocessor
reserve memory.</p></li>
</ol>
</div>
</section>
</section>
<section id="bit-timers">
<h2>64-bit Timers<a class="headerlink" href="#bit-timers" title="Permalink to this heading"></a></h2>
<p>ESP32 has 4 generic timers of 64 bits (2 from Group 0 and 2 from Group 1). They’re
accessible as character drivers, the configuration along with a guidance on how
to run the example and the description of the application level interface
can be found <a class="reference internal" href="../../../components/drivers/character/timers/timer.html"><span class="doc">here</span></a>.</p>
</section>
<section id="watchdog-timers">
<h2>Watchdog Timers<a class="headerlink" href="#watchdog-timers" title="Permalink to this heading"></a></h2>
<p>ESP32 has 3 WDTs. 2 MWDTS from the Timers Module and 1 RWDT from the RTC Module
(Currently not supported yet). They’re accessible as character drivers,
The configuration along with a guidance on how to run the example and the description
of the application level interface can be found
<a class="reference internal" href="../../../components/drivers/character/timers/watchdog.html"><span class="doc">here</span></a>.</p>
</section>
<section id="smp">
<h2>SMP<a class="headerlink" href="#smp" title="Permalink to this heading"></a></h2>
<p>The ESP32 has 2 CPUs. Support is included for testing an SMP configuration.
That configuration is still not yet ready for usage but can be enabled with
the following configuration settings,
in <span class="menuselection">RTOS Features ‣ Tasks and Scheduling</span>, with:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>CONFIG_SPINLOCK=y
CONFIG_SMP=y
CONFIG_SMP_NCPUS=2
</pre></div>
</div>
<p>Debug Tip: During debug session, OpenOCD may mysteriously switch from one
CPU to another. This behavior can be eliminated by uncommenting one of the
following in <code class="docutils literal notranslate"><span class="pre">scripts/esp32.cfg</span></code>:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span># Only configure the PRO CPU
#set ESP32_ONLYCPU 1
# Only configure the APP CPU
#set ESP32_ONLYCPU 2
</pre></div>
</div>
</section>
<section id="wi-fi">
<span id="esp32-wi-fi-sta"></span><h2>Wi-Fi<a class="headerlink" href="#wi-fi" title="Permalink to this heading"></a></h2>
<p>A standard network interface will be configured and can be initialized such as:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>nsh&gt; ifup wlan0
nsh&gt; wapi psk wlan0 mypasswd 3
nsh&gt; wapi essid wlan0 myssid 1
nsh&gt; renew wlan0
</pre></div>
</div>
<p>In this case a connection to AP with SSID <code class="docutils literal notranslate"><span class="pre">myssid</span></code> is done, using <code class="docutils literal notranslate"><span class="pre">mypasswd</span></code> as
password. IP address is obtained via DHCP using <code class="docutils literal notranslate"><span class="pre">renew</span></code> command. You can check
the result by running <code class="docutils literal notranslate"><span class="pre">ifconfig</span></code> afterwards.</p>
<div class="admonition tip">
<p class="admonition-title">Tip</p>
<p>Boards usually expose a <code class="docutils literal notranslate"><span class="pre">wifi</span></code> defconfig which enables Wi-Fi</p>
</div>
<div class="admonition tip">
<p class="admonition-title">Tip</p>
<p>Please check <a class="reference internal" href="../../../applications/wireless/wapi/index.html"><span class="doc">wapi</span></a> documentation for more
information about its commands and arguments.</p>
</div>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>The <code class="docutils literal notranslate"><span class="pre">wapi</span> <span class="pre">psk</span></code> command on Station mode sets a security threshold. That
is, it enables connecting only to an equally or more secure network than the set
threshold. <code class="docutils literal notranslate"><span class="pre">wapi</span> <span class="pre">psk</span> <span class="pre">wlan0</span> <span class="pre">mypasswd</span> <span class="pre">3</span></code> sets a WPA2-PSK-secured network and
enables the device to connect to networks that are equally or more secure than
that (WPA3-SAE, for instance, would be eligible for connecting to).</p>
</div>
</section>
<section id="wi-fi-softap">
<span id="esp32-wi-fi-softap"></span><h2>Wi-Fi SoftAP<a class="headerlink" href="#wi-fi-softap" title="Permalink to this heading"></a></h2>
<p>It is possible to use ESP32 as an Access Point (SoftAP). Actually there are some
boards config examples called sta_softap which enables this support</p>
<p>If you are using this board config profile you can run these commands to be able
to connect your smartphone or laptop to your board:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>nsh&gt; ifup wlan1
nsh&gt; dhcpd_start wlan1
nsh&gt; wapi psk wlan1 mypasswd 3
nsh&gt; wapi essid wlan1 nuttxap 1
</pre></div>
</div>
<p>In this case, you are creating the access point <code class="docutils literal notranslate"><span class="pre">nuttxapp</span></code> in your board and to
connect to it on your smartphone you will be required to type the password <code class="docutils literal notranslate"><span class="pre">mypasswd</span></code>
using WPA2.</p>
<div class="admonition tip">
<p class="admonition-title">Tip</p>
<p>Please check <a class="reference internal" href="../../../applications/wireless/wapi/index.html"><span class="doc">wapi</span></a> documentation for more
information about its commands and arguments.</p>
</div>
<p>The <code class="docutils literal notranslate"><span class="pre">dhcpd_start</span></code> is necessary to let your board to associate an IP to your smartphone.</p>
</section>
<section id="bluetooth">
<h2>Bluetooth<a class="headerlink" href="#bluetooth" title="Permalink to this heading"></a></h2>
<p>These are the steps to test Bluetooth Low Energy (BLE) scan on ESP32 (i.e. Devkit board).
First configure to use the BLE board profile:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>$ make distclean
$ ./tools/configure.sh esp32-devkitc:ble
$ make flash ESPTOOL_PORT=/dev/ttyUSB0
</pre></div>
</div>
<p>Enter in the NSH shell using your preferred serial console tool and run the scan command:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>NuttShell (NSH) NuttX-10.2.0
nsh&gt; ifconfig
bnep0 Link encap:UNSPEC at DOWN
inet addr:0.0.0.0 DRaddr:0.0.0.0 Mask:0.0.0.0
wlan0 Link encap:Ethernet HWaddr ac:67:b2:53:8b:ec at UP
inet addr:10.0.0.2 DRaddr:10.0.0.1 Mask:255.255.255.0
nsh&gt; bt bnep0 scan start
nsh&gt; bt bnep0 scan stop
nsh&gt; bt bnep0 scan get
Scan result:
1. addr: 63:14:2f:b9:9f:83 type: 1
rssi: -90
response type: 3
advertiser data: 1e ff 06 00 01 09 20 02 7c 33 a3 a7 cd c9 44 5b
2. addr: 52:ca:05:b5:ad:77 type: 1
rssi: -82
response type: 3
advertiser data: 1e ff 06 00 01 09 20 02 03 d1 21 57 bf 19 b3 7a
3. addr: 46:8e:b2:cd:94:27 type: 1
rssi: -92
response type: 2
advertiser data: 02 01 1a 09 ff c4 00 10 33 14 12 16 80 02 0a d4
4. addr: 46:8e:b2:cd:94:27 type: 1
rssi: -92
response type: 4
advertiser data: 18 09 5b 4c 47 5d 20 77 65 62 4f 53 20 54 56 20
5. addr: 63:14:2f:b9:9f:83 type: 1
rssi: -80
response type: 3
advertiser data: 1e ff 06 00 01 09 20 02 7c 33 a3 a7 cd c9 44 5b
nsh&gt;
</pre></div>
</div>
</section>
<section id="i2s">
<h2>I2S<a class="headerlink" href="#i2s" title="Permalink to this heading"></a></h2>
<p>The I2S peripheral is accessible using either the generic I2S audio driver or a specific
audio codec driver. Also, it’s possible to use the I2S character driver to bypass the
audio subsystem and develop specific usages of the I2S peripheral.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>Note that the bit-width and sample rate can be modified “on-the-go” when using
audio-related drivers. That is not the case for the I2S character device driver and
such parameters are set on compile time through <cite>make menuconfig</cite>.</p>
</div>
<div class="admonition warning">
<p class="admonition-title">Warning</p>
<p>Some upper driver implementations might not handle both transmission and
reception configured at the same time on the same peripheral.</p>
</div>
<p>Please check for usage examples using the <a class="reference internal" href="boards/esp32-devkitc/index.html"><span class="doc">ESP32 DevKitC</span></a>.</p>
</section>
<section id="using-qemu">
<h2>Using QEMU<a class="headerlink" href="#using-qemu" title="Permalink to this heading"></a></h2>
<p>Get or build QEMU from <a class="reference external" href="https://github.com/espressif/qemu/wiki">here</a>.</p>
<p>Enable the <code class="docutils literal notranslate"><span class="pre">ESP32_QEMU_IMAGE</span></code> config found in <span class="menuselection">Board Selection ‣ ESP32 binary image for QEMU</span>.</p>
<p>Build and generate the QEMU image:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>$ make bootloader
$ make ESPTOOL_BINDIR=.
</pre></div>
</div>
<p>A QEMU-compatible <code class="docutils literal notranslate"><span class="pre">nuttx.merged.bin</span></code> binary image will be created. It can be run as:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>$ qemu-system-xtensa -nographic -machine esp32 -drive file=nuttx.merged.bin,if=mtd,format=raw
</pre></div>
</div>
<p>QEMU for ESP32 does not correctly define the chip revision as v3.0 so you have two options:</p>
<ul class="simple">
<li><p>#define <code class="docutils literal notranslate"><span class="pre">ESP32_IGNORE_CHIP_REVISION_CHECK</span></code> in <code class="docutils literal notranslate"><span class="pre">arch/xtensa/src/esp32/esp32_start.c</span></code></p></li>
<li><p>Emulate the efuse as described <a class="reference external" href="https://github.com/espressif/esp-toolchain-docs/blob/main/qemu/esp32/README.md#emulating-esp32-eco3">here</a>.</p></li>
</ul>
<section id="qemu-networking">
<h3>QEMU Networking<a class="headerlink" href="#qemu-networking" title="Permalink to this heading"></a></h3>
<p>Networking is possible using the openeth MAC driver. Enable <code class="docutils literal notranslate"><span class="pre">ESP32_OPENETH</span></code> option and set the nic in QEMU:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>$ qemu-system-xtensa -nographic -machine esp32 -drive file=nuttx.merged.bin,if=mtd,format=raw -nic user,model=open_eth
</pre></div>
</div>
</section>
</section>
<section id="secure-boot-and-flash-encryption">
<h2>Secure Boot and Flash Encryption<a class="headerlink" href="#secure-boot-and-flash-encryption" title="Permalink to this heading"></a></h2>
<section id="secure-boot">
<h3>Secure Boot<a class="headerlink" href="#secure-boot" title="Permalink to this heading"></a></h3>
<p>Secure Boot protects a device from running any unauthorized (i.e., unsigned) code by checking that
each piece of software that is being booted is signed. On an ESP32, these pieces of software include
the second stage bootloader and each application binary. Note that the first stage bootloader does not
require signing as it is ROM code thus cannot be changed. This is achieved using specific hardware in
conjunction with MCUboot (read more about MCUboot <a class="reference external" href="https://docs.mcuboot.com/">here</a>).</p>
<p>The Secure Boot process on the ESP32 involves the following steps performed:</p>
<ol class="arabic simple">
<li><p>The first stage bootloader verifies the second stage bootloader’s RSA-PSS signature. If the verification is successful,
the first stage bootloader loads and executes the second stage bootloader.</p></li>
<li><p>When the second stage bootloader loads a particular application image, the application’s signature (RSA, ECDSA or ED25519) is verified
by MCUboot.
If the verification is successful, the application image is executed.</p></li>
</ol>
<div class="admonition warning">
<p class="admonition-title">Warning</p>
<p>Once enabled, Secure Boot will not boot a modified bootloader. The bootloader will only boot an
application firmware image if it has a verified digital signature. There are implications for reflashing
updated images once Secure Boot is enabled. You can find more information about the ESP32’s Secure boot
<a class="reference external" href="https://docs.espressif.com/projects/esp-idf/en/latest/esp32/security/secure-boot-v2.html">here</a>.</p>
</div>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>As the bootloader image is built on top of the Hardware Abstraction Layer component
of <a class="reference external" href="https://github.com/espressif/esp-idf">ESP-IDF</a>, the
<a class="reference external" href="https://docs.mcuboot.com/readme-espressif.html">API port by Espressif</a> will be used
by MCUboot rather than the original NuttX port.</p>
</div>
</section>
<section id="flash-encryption">
<h3>Flash Encryption<a class="headerlink" href="#flash-encryption" title="Permalink to this heading"></a></h3>
<p>Flash encryption is intended for encrypting the contents of the ESP32’s off-chip flash memory. Once this feature is enabled,
firmware is flashed as plaintext, and then the data is encrypted in place on the first boot. As a result, physical readout
of flash will not be sufficient to recover most flash contents.</p>
<div class="admonition warning">
<p class="admonition-title">Warning</p>
<p>After enabling Flash Encryption, an encryption key is generated internally by the device and
cannot be accessed by the user for re-encrypting data and re-flashing the system, hence it will be permanently encrypted.
Re-flashing an encrypted system is complicated and not always possible. You can find more information about the ESP32’s Flash Encryption
<a class="reference external" href="https://docs.espressif.com/projects/esp-idf/en/latest/esp32/security/flash-encryption.html">here</a>.</p>
</div>
</section>
<section id="prerequisites">
<h3>Prerequisites<a class="headerlink" href="#prerequisites" title="Permalink to this heading"></a></h3>
<p>First of all, we need to install <code class="docutils literal notranslate"><span class="pre">imgtool</span></code> (a MCUboot utility application to manipulate binary
images) and <code class="docutils literal notranslate"><span class="pre">esptool</span></code> (the ESP32 toolkit):</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>$ pip install imgtool esptool==4.8.dev4
</pre></div>
</div>
<p>We also need to make sure that the python modules are added to <code class="docutils literal notranslate"><span class="pre">PATH</span></code>:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>$ echo &quot;PATH=$PATH:/home/$USER/.local/bin&quot; &gt;&gt; ~/.bashrc
</pre></div>
</div>
<p>Now, we will create a folder to store the generated keys (such as <code class="docutils literal notranslate"><span class="pre">~/signing_keys</span></code>):</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>$ mkdir ~/signing_keys &amp;&amp; cd ~/signing_keys
</pre></div>
</div>
<p>With all set up, we can now generate keys to sign the bootloader and application binary images,
respectively, of the compiled project:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>$ espsecure.py generate_signing_key --version 2 bootloader_signing_key.pem
$ imgtool keygen --key app_signing_key.pem --type rsa-3072
</pre></div>
</div>
<div class="admonition important">
<p class="admonition-title">Important</p>
<p>The contents of the key files must be stored securely and kept secret.</p>
</div>
</section>
<section id="enabling-secure-boot-and-flash-encryption">
<h3>Enabling Secure Boot and Flash Encryption<a class="headerlink" href="#enabling-secure-boot-and-flash-encryption" title="Permalink to this heading"></a></h3>
<p>To enable Secure Boot for the current project, go to the project’s NuttX directory, execute <code class="docutils literal notranslate"><span class="pre">make</span> <span class="pre">menuconfig</span></code> and the following steps:</p>
<blockquote>
<div><ol class="arabic simple">
<li><p>Enable experimental features in <span class="menuselection">Build Setup ‣ Show experimental options</span>;</p></li>
<li><p>Enable MCUboot in <span class="menuselection">Application Configuration ‣ Bootloader Utilities ‣ MCUboot</span>;</p></li>
<li><p>Change image type to <code class="docutils literal notranslate"><span class="pre">MCUboot-bootable</span> <span class="pre">format</span></code> in <span class="menuselection">System Type ‣ Application Image Configuration ‣ Application Image Format</span>;</p></li>
<li><p>Enable building MCUboot from the source code by selecting <code class="docutils literal notranslate"><span class="pre">Build</span> <span class="pre">binaries</span> <span class="pre">from</span> <span class="pre">source</span></code>;
in <span class="menuselection">System Type ‣ Application Image Configuration ‣ Source for bootloader binaries</span>;</p></li>
<li><p>Enable Secure Boot in <span class="menuselection">System Type ‣ Application Image Configuration ‣ Enable hardware Secure Boot in bootloader</span>;</p></li>
<li><p>If you want to protect the SPI Bus against data sniffing, you can enable Flash Encryption in
<span class="menuselection">System Type ‣ Application Image Configuration ‣ Enable Flash Encryption on boot</span>.</p></li>
</ol>
</div></blockquote>
<p>Now you can design an update and confirm agent to your application. Check the <a class="reference external" href="https://docs.mcuboot.com/design.html">MCUboot design guide</a> and the
<a class="reference external" href="https://docs.mcuboot.com/readme-espressif.html">MCUboot Espressif port documentation</a> for
more information on how to apply MCUboot. Also check some <a class="reference external" href="https://github.com/mcu-tools/mcuboot/blob/main/docs/readme-nuttx.md">notes about the NuttX MCUboot port</a>,
the <a class="reference external" href="https://github.com/mcu-tools/mcuboot/blob/main/docs/PORTING.md">MCUboot porting guide</a> and some
<a class="reference external" href="https://github.com/apache/nuttx-apps/tree/master/examples/mcuboot">examples of MCUboot applied in NuttX applications</a>.</p>
<p>After you developed an application which implements all desired functions, you need to flash it into the primary image slot
of the device (it will automatically be in the confirmed state, you can learn more about image
confirmation <a class="reference external" href="https://docs.mcuboot.com/design.html#image-swapping">here</a>).
To flash to the primary image slot, select <code class="docutils literal notranslate"><span class="pre">Application</span> <span class="pre">image</span> <span class="pre">primary</span> <span class="pre">slot</span></code> in
<span class="menuselection">System Type ‣ Application Image Configuration ‣ Target slot for image flashing</span>
and compile it using <code class="docutils literal notranslate"><span class="pre">make</span> <span class="pre">-j</span> <span class="pre">ESPSEC_KEYDIR=~/signing_keys</span></code>.</p>
<p>When creating update images, make sure to change <span class="menuselection">System Type ‣ Application Image Configuration ‣ Target slot for image flashing</span>
to <code class="docutils literal notranslate"><span class="pre">Application</span> <span class="pre">image</span> <span class="pre">secondary</span> <span class="pre">slot</span></code>.</p>
<div class="admonition important">
<p class="admonition-title">Important</p>
<p>When deploying your application, make sure to disable UART Download Mode by selecting <code class="docutils literal notranslate"><span class="pre">Permanently</span> <span class="pre">disabled</span></code> in
<span class="menuselection">System Type ‣ Application Image Configuration ‣ UART ROM download mode</span>
and change usage mode to <code class="docutils literal notranslate"><span class="pre">Release</span></code> in <cite>System Type –&gt; Application Image Configuration –&gt; Enable usage mode</cite>.
<strong>After disabling UART Download Mode you will not be able to flash other images through UART.</strong></p>
</div>
</section>
</section>
<section id="things-to-do">
<h2>Things to Do<a class="headerlink" href="#things-to-do" title="Permalink to this heading"></a></h2>
<ol class="arabic">
<li><p>Lazy co-processor save logic supported by Xtensa. That logic works like this:</p>
<ol class="loweralpha simple">
<li><p>CPENABLE is set to zero on each context switch, disabling all co-
processors.</p></li>
<li><p>If/when the task attempts to use the disabled co-processor, an
exception occurs</p></li>
<li><p>The co-processor exception handler re-enables the co-processor.</p></li>
</ol>
<p>Instead, the NuttX logic saves and restores CPENABLE on each context
switch. This has disadvantages in that (1) co-processor context will
be saved and restored even if the co-processor was never used, and (2)
tasks must explicitly enable and disable co-processors.</p>
</li>
<li><p>Currently the Xtensa port copies register state save information from
the stack into the TCB. A more efficient alternative would be to just
save a pointer to a register state save area in the TCB. This would
add some complexity to signal handling and also to up_initialstate().
But the performance improvement might be worth the effort.</p></li>
<li><p>See SMP-related issues above</p></li>
</ol>
</section>
<section id="supported-boards">
<h2>Supported Boards<a class="headerlink" href="#supported-boards" title="Permalink to this heading"></a></h2>
<div class="toctree-wrapper compound">
<ul>
<li class="toctree-l1"><a class="reference internal" href="boards/esp32-2432S028/index.html">ESP32-2432S028</a></li>
<li class="toctree-l1"><a class="reference internal" href="boards/esp32-audio-kit/index.html">ESP32-AUDIO-KIT</a></li>
<li class="toctree-l1"><a class="reference internal" href="boards/esp32-devkitc/index.html">ESP32 DevKitC</a></li>
<li class="toctree-l1"><a class="reference internal" href="boards/esp32-ethernet-kit/index.html">ESP32-Ethernet-Kit V1.2</a></li>
<li class="toctree-l1"><a class="reference internal" href="boards/esp32-lyrat/index.html">ESP32-LyraT V4.3</a></li>
<li class="toctree-l1"><a class="reference internal" href="boards/esp32-pico-kit/index.html">ESP32-PICO-KIT V4</a></li>
<li class="toctree-l1"><a class="reference internal" href="boards/esp32-wrover-kit/index.html">ESP-WROVER-KIT</a></li>
</ul>
</div>
</section>
</section>
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