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| <section id="socketcan-device-drivers"> |
| <h1>SocketCAN Device Drivers<a class="headerlink" href="#socketcan-device-drivers" title="Permalink to this heading"></a></h1> |
| <blockquote> |
| <div><ul> |
| <li><p><code class="docutils literal notranslate"><span class="pre">include/nuttx/net/netdev.h</span></code>. All structures and APIs |
| needed to work with drivers are provided in this header file. |
| The structure struct net_driver_s defines the interface and is |
| passed to the network via netdev_register().</p></li> |
| <li><p><code class="docutils literal notranslate"><span class="pre">include/nuttx/can.h</span></code>. CAN & CAN FD frame data |
| structures.</p></li> |
| <li><p><code class="docutils literal notranslate"><span class="pre">int</span> <span class="pre">netdev_register(FAR</span> <span class="pre">struct</span> <span class="pre">net_driver_s</span> <span class="pre">*dev,</span> <span class="pre">enum</span> <span class="pre">net_lltype_e</span> <span class="pre">lltype)'</span></code>. |
| Each driver registers itself by calling netdev_register().</p></li> |
| <li><p><code class="docutils literal notranslate"><span class="pre">Include/nuttx/net/can.h</span></code>. contains lookup tables for CAN |
| dlc to CAN FD len sizes named</p> |
| <div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="k">extern</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="kt">uint8_t</span><span class="w"> </span><span class="n">can_dlc_to_len</span><span class="p">[</span><span class="mi">16</span><span class="p">];</span> |
| <span class="k">extern</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="kt">uint8_t</span><span class="w"> </span><span class="n">len_to_can_dlc</span><span class="p">[</span><span class="mi">65</span><span class="p">];</span> |
| </pre></div> |
| </div> |
| </li> |
| <li><p><strong>Initialization sequence is as follows</strong>.</p> |
| <ol class="arabic simple"> |
| <li><p>up_netinitialize(void) is called on startup of NuttX in this |
| function you call your own init function to initialize your |
| CAN driver</p></li> |
| <li><p>In your own init function you create the net_driver_s |
| structure set required init values and register the required |
| callbacks for SocketCAN</p></li> |
| <li><p>Then you ensure that the CAN interface is in down mode |
| (usually done by calling the d_ifdown function)</p></li> |
| <li><p>Register the net_driver_s using netdev_register</p></li> |
| </ol> |
| </li> |
| <li><p><strong>Receive sequence is as follows</strong>.</p> |
| <ol class="arabic simple"> |
| <li><p>Device generates interrupt</p></li> |
| <li><p>Process this interrupt in your interrupt handler</p></li> |
| <li><p>When a new CAN frame has been received you process this |
| frame</p></li> |
| <li><p>When the CAN frame is a normal CAN frame you allocate the |
| can_frame struct, when it’s a CAN FD frame you allocate a |
| canfd_frame struct (note you can of course preallocate and |
| just use the pointer).</p></li> |
| <li><p>Copy the frame from the driver to the struct you’ve |
| allocated in the previous step.</p></li> |
| <li><p>Point the net_driver_s d_buf pointer to the allocated |
| can_frame</p></li> |
| <li><p>Call the <code class="docutils literal notranslate"><span class="pre">can_input(FAR</span> <span class="pre">struct</span> <span class="pre">net_driver_s</span> <span class="pre">*dev)</span></code> |
| function <code class="docutils literal notranslate"><span class="pre">include/nuttx/net/can.h</span></code></p></li> |
| </ol> |
| </li> |
| <li><p><strong>Transmit sequence is as follows</strong>.</p> |
| <ol class="arabic simple"> |
| <li><p>Socket layer executes d_txavail callback</p></li> |
| <li><p>An example of the txavail function can be found in |
| <code class="docutils literal notranslate"><span class="pre">arch/arm/src/s32k1xx/s32k1xx_flexcan.c</span></code></p></li> |
| <li><p>An example of the txpoll function can be found in |
| <code class="docutils literal notranslate"><span class="pre">arch/arm/src/s32k1xx/s32k1xx_flexcan.c</span></code></p></li> |
| <li><p>In your <code class="docutils literal notranslate"><span class="pre">transmit(struct</span> <span class="pre">driver_s</span> <span class="pre">*priv)</span></code> function you |
| check the length of <code class="docutils literal notranslate"><span class="pre">net_driver_s.d_len</span></code> whether it |
| matches the size of a <code class="docutils literal notranslate"><span class="pre">struct</span> <span class="pre">can_frame</span></code> or |
| <code class="docutils literal notranslate"><span class="pre">struct</span> <span class="pre">canfd_frame</span></code> then you cast the content of the |
| <code class="docutils literal notranslate"><span class="pre">net_driver_s.d_buf</span></code> pointer to the correct CAN frame |
| struct</p></li> |
| </ol> |
| </li> |
| </ul> |
| </div></blockquote> |
| </section> |
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