<p>Last article we got <strong>LoRa</strong> (the long-range, low-bandwidth wireless network) running on <ahref="https://lupyuen.github.io/articles/nuttx"><strong>Apache NuttX OS</strong></a>…</p>
<p>We shall test LoRaWAN on NuttX with Bouffalo Lab’s <ahref="https://lupyuen.github.io/articles/pinecone"><strong>BL602 and BL604 RISC-V SoCs</strong></a>.</p>
<p>(It will probably run on <strong>ESP32</strong>, since we’re calling standard NuttX Interfaces)</p>
<p><imgsrc="https://lupyuen.github.io/images/sx1262-library5.jpg"alt="Porting LoRaWAN to NuttX OS"/></p>
<p>LoRaWAN works <strong>slightly differently across the world regions</strong>, to comply with Local Wireless Regulations: Radio Frequency, Maximum Airtime (Duty Cycle), <ahref="https://lupyuen.github.io/articles/lorawan#appendix-lora-carrier-sensing">Listen Before Talk</a>, …</p>
<p>Thus we should port <strong>Semtech’s LoRaWAN Stack</strong> to NuttX with <strong>minimal changes</strong>, in case of future updates. (Like for new regions)</p>
<p>This also means that we should port <strong>Semtech’s SX1262 Driver</strong> to NuttX as-is, because of the dependencies between the LoRaWAN Stack and the SX1262 Driver.</p>
<p>Note that we’re using the older <strong>“nuttx”</strong> branch of the “lora_sx1262” repo, which <ahref="https://lupyuen.github.io/articles/sx1262#appendix-previous-sx1262-library"><strong>doesn’t use GPIO Interface and NimBLE Porting Layer</strong></a>. (And doesn’t support LoRaWAN)</p>
<h2id="library-vs-driver"class="section-header"><ahref="#library-vs-driver">1.3 Library vs Driver</a></h2>
<p><em>NuttX Libraries vs Drivers… What’s the difference?</em></p>
<p>Our LoRa SX1262 code is initially packaged as a <strong>NuttX Library</strong> (instead of NuttX Driver) because…</p>
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<p>NuttX Libraries are <strong>easier to code and troubleshoot</strong></p>
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<p>NuttX Libraries may be called by <strong>NuttX Apps AND NuttX Drivers</strong></p>
<p>(So we can test our library with a NuttX App)</p>
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</ul>
<p>Eventually our LoRa SX1262 code shall be packaged as a <strong>NuttX Driver</strong>…</p>
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<p>Our code shall run inside NuttX OS, which means…</p>
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<p>Our driver needs to expose an <strong>ioctl()</strong> interface to NuttX Apps</p>
<p>(Which will be cumbersome to code)</p>
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</ul>
<p>Check out the <strong>ioctl()</strong> interface for the existing SX1276 Driver in NuttX: <ahref="https://github.com/apache/incubator-nuttx/blob/master/drivers/wireless/lpwan/sx127x/sx127x.c#L954-L1162"><strong>sx127x.c</strong></a></p>
<p><imgsrc="https://lupyuen.github.io/images/spi2-plan2.jpg"alt="SPI Test Driver"/></p>
<p><em>But how will our library access the NuttX SPI Interface?</em></p>
<p>The NuttX SPI Interface is accessible by NuttX Drivers, but not NuttX Apps.</p>
<p>Thankfully in the previous article we have created an <strong>SPI Test Driver “/dev/spitest0”</strong> that exposes the SPI Interface to NuttX Apps (pic above)…</p>
<ul>
<li><ahref="https://lupyuen.github.io/articles/spi2"><strong>“SPI on Apache NuttX OS”</strong></a></li>
</ul>
<p>For now we’ll call this SPI Test Driver in our LoRa SX1262 Library.</p>
<p><em>We’re porting plenty of code to NuttX: LoRa, LoRaWAN and NimBLE Porting Layer. Do we expect any problems?</em></p>
<p>Yep we might have issues keeping our LoRaWAN Stack in sync with Semtech’s version. <ahref="https://lupyuen.github.io/articles/sx1262#notes">(But we shall minimise the changes)</a></p>
<p>Stay Tuned!</p>
<p>Many Thanks to my <ahref="https://github.com/sponsors/lupyuen"><strong>GitHub Sponsors</strong></a> for supporting my work! This article wouldn’t have been possible without your support.</p>
<ul>
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<p><ahref="https://github.com/sponsors/lupyuen">Sponsor me a coffee</a></p>
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<p><ahref="https://lupyuen.github.io/articles/book">Read “The RISC-V BL602 / BL604 Book”</a></p>
</li>
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<p><ahref="https://lupyuen.github.io">Check out my articles</a></p>
<p>This article is the expanded version of <ahref="https://twitter.com/MisterTechBlog/status/1473593455699841027">this Twitter Thread</a></p>
</li>
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<p>We’re <strong>porting plenty of code</strong> to NuttX: LoRa, LoRaWAN and NimBLE Porting Layer. Do we expect any problems?</p>
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<p>If we implement LoRa and LoRaWAN as <strong>NuttX Drivers</strong>, we’ll have to scrub the code to comply with the <ahref="https://nuttx.apache.org/docs/latest/contributing/coding_style.html"><strong>NuttX Coding Conventions</strong></a>.</p>
<p>This makes it <strong>harder to update</strong> the LoRaWAN Driver when there are changes in the LoRaWAN Spec. (Like for a new LoRaWAN Region)</p>
<p><ahref="https://lupyuen.github.io/articles/lorawan#appendix-lora-carrier-sensing">(Here’s an example)</a></p>
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<p>Alternatively we may implement LoRa and LoRaWAN as <strong>External Libraries</strong>, similar to <ahref="https://github.com/lupyuen/incubator-nuttx-apps/tree/master/wireless/bluetooth/nimble"><strong>NimBLE for NuttX</strong></a>.</p>
<p>(The <ahref="https://github.com/lupyuen/incubator-nuttx-apps/blob/master/wireless/bluetooth/nimble/Makefile#L33"><strong>Makefile</strong></a> downloads the External Library during build)</p>
<p>But then we won’t get a proper NuttX Driver that exposes the ioctl() interface to NuttX Apps.</p>
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</ul>
<p>Conundrum. Lemme know your thoughts!</p>
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<p>How do other Embedded Operating Systems implement LoRaWAN?</p>
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<p><strong>Mynewt</strong> embeds a <ahref="https://github.com/apache/mynewt-core/tree/master/net/lora/node"><strong>Partial Copy</strong></a> of Semtech’s LoRaWAN Stack into its source tree.</p>
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<p><strong>Zephyr</strong> maintains a <ahref="https://github.com/zephyrproject-rtos/loramac-node"><strong>Complete Fork</strong></a> of the entire LoRaWAN Repo by Semtech. Which gets embedded during the Zephyr build.</p>
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</ul>
<p>The Zephyr approach is probably the best way to <strong>keep our LoRaWAN Stack in sync</strong> with Semtech’s.</p>
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<p>We have already ported LoRaWAN to <strong>BL602 IoT SDK</strong><ahref="https://lupyuen.github.io/articles/lorawan">(see this)</a>, why are we porting again to NuttX?</p>
<p>Regrettably BL602 IoT SDK has been revamped (without warning) to the <strong>new “hosal” HAL</strong><ahref="https://twitter.com/MisterTechBlog/status/1456259223323508748">(see this)</a>, and the LoRaWAN Stack will <strong>no longer work</strong> on the revamped BL602 IoT SDK.</p>
<p>For easier maintenance, we shall <strong>code our BL602 and BL604 projects with Apache NuttX OS</strong> instead.</p>
<p>(Which won’t get revamped overnight!)</p>
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<p>Will NuttX become the official OS for PineDio Stack BL604 when it goes on sale?</p>
<p>It might! But first let’s get LoRaWAN (and ST7789) running on PineDio Stack.</p>
