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<title>ESP MODEM — esp-modem documentation</title>
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<section id="esp-modem">
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<h1>ESP MODEM<a class="headerlink" href="#esp-modem" title="Permalink to this headline">¶</a></h1>
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<p>This component is used to communicate with modems in the command mode (using AT commands), as well as the data mode
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(over PPPoS protocol).
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The modem device is modeled with a DCE (Data Communication Equipment) object, which is composed of:</p>
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<ul class="simple">
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<li><p>DTE (Data Terminal Equipment), which abstracts the terminal (currently only UART implemented).</p></li>
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<li><p>PPP Netif representing a network interface communicating with the DTE using PPP protocol.</p></li>
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<li><p>Module abstracting the specific device model and its commands.</p></li>
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</ul>
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<div class="highlight-default notranslate"><div class="highlight"><pre><span></span> <span class="o">+-----+</span>
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<span class="o">|</span> <span class="n">DTE</span> <span class="o">|--+</span>
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<span class="o">+-----+</span> <span class="o">|</span> <span class="o">+-------+</span>
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<span class="o">+-->|</span> <span class="n">DCE</span> <span class="o">|</span>
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<span class="o">+-------+</span> <span class="o">|</span> <span class="o">|</span><span class="n">o</span><span class="o">---</span> <span class="n">set_mode</span><span class="p">(</span><span class="n">command</span><span class="o">/</span><span class="n">data</span><span class="p">)</span>
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<span class="o">|</span> <span class="n">Module</span><span class="o">|--->|</span> <span class="o">|</span>
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<span class="o">+-------+</span> <span class="o">|</span> <span class="o">|</span><span class="n">o</span><span class="o">---</span> <span class="n">send_commands</span>
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<span class="o">+->|</span> <span class="o">|</span>
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<span class="o">+------+</span> <span class="o">|</span> <span class="o">+-------+</span>
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<span class="o">|</span> <span class="n">PPP</span> <span class="o">|--+</span>
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<span class="o">|</span> <span class="n">netif</span><span class="o">|------------------></span> <span class="n">network</span> <span class="n">events</span>
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<span class="o">+------+</span>
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</pre></div>
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</div>
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<section id="modem-components">
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<h2>Modem components<a class="headerlink" href="#modem-components" title="Permalink to this headline">¶</a></h2>
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<section id="dce">
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<h3>DCE<a class="headerlink" href="#dce" title="Permalink to this headline">¶</a></h3>
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<p>This is the basic operational unit of the esp_modem component, abstracting a specific module in software,
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which is basically configured by</p>
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<ul class="simple">
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<li><p>the I/O communication media (UART), defined by the DTE configuration</p></li>
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<li><p>the specific command library supported by the device model, defined with the module type</p></li>
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<li><p>network interface configuration (PPPoS config in lwip)</p></li>
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</ul>
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<p>After the object is created, the application interaction with the DCE is in</p>
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<ul class="simple">
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<li><p>issuing specific commands to the modem</p></li>
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<li><p>switching between data and command mode</p></li>
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</ul>
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</section>
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<section id="dte">
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<h3>DTE<a class="headerlink" href="#dte" title="Permalink to this headline">¶</a></h3>
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<p>Is an abstraction of the physical interface connected to the modem. Current implementation supports only UART</p>
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</section>
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<section id="ppp-netif">
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<h3>PPP netif<a class="headerlink" href="#ppp-netif" title="Permalink to this headline">¶</a></h3>
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<p>Is used to attach the specific network interface to a network communication protocol used by the modem. Currently implementation supports only PPPoS protocol.</p>
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</section>
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<section id="module">
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<h3>Module<a class="headerlink" href="#module" title="Permalink to this headline">¶</a></h3>
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<p>Abstraction of the specific modem device. Currently the component supports SIM800, BG96, SIM7600.</p>
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</section>
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</section>
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<section id="use-cases">
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<h2>Use cases<a class="headerlink" href="#use-cases" title="Permalink to this headline">¶</a></h2>
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<p>Users interact with the esp-modem using the DCE’s interface, to basically</p>
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<ul class="simple">
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<li><p>Switch between command and data mode to connect to the internet via cellular network.</p></li>
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<li><p>Send various commands to the device (e.g. send SMS)</p></li>
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</ul>
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<p>The applications typically register handlers for network events to receive notification on the network availability and
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IP address changes.</p>
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<p>Common use cases of the esp-modem are also listed as the examples:</p>
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<ul class="simple">
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<li><p><code class="docutils literal notranslate"><span class="pre">examples/pppos_client</span></code> – simple client which reads some module properties and switches to the data mode to connect to a public mqtt broker.</p></li>
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<li><p><code class="docutils literal notranslate"><span class="pre">examples/modem_console</span></code> – is an example to exercise all possible module commands in a console application.</p></li>
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<li><p><code class="docutils literal notranslate"><span class="pre">examples/ap_to_pppos</span></code> – this example focuses on the network connectivity of the esp-modem and provides a WiFi AP that forwards packets (and uses NAT) to and from the PPPoS connection.</p></li>
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</ul>
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</section>
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<section id="extensibility">
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<h2>Extensibility<a class="headerlink" href="#extensibility" title="Permalink to this headline">¶</a></h2>
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<section id="cmux">
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<h3>CMUX<a class="headerlink" href="#cmux" title="Permalink to this headline">¶</a></h3>
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<p>Implementation of virtual terminals is an experimental feature, which allows users to also issue commands in the data mode,
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after creating multiple virtual terminals, designating some of them solely to data mode, others solely to command mode.</p>
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</section>
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<section id="dte-s">
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<h3>DTE’s<a class="headerlink" href="#dte-s" title="Permalink to this headline">¶</a></h3>
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<p>Currently we support only UART, but modern modules support other communication interfaces, such as USB, SPI.</p>
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</section>
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<section id="other-devices">
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<h3>Other devices<a class="headerlink" href="#other-devices" title="Permalink to this headline">¶</a></h3>
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<p>Adding a new device is a must-have requirement for the esp-modem component. Different modules support different commands,
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or some commands might have a different implementation. Adding a new device means to provide a new implementation
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as a class derived from <code class="docutils literal notranslate"><span class="pre">GenericModule</span></code>, where we could add new commands or modify the existing ones.</p>
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</section>
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</section>
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</section>
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</div>
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<div class="sphinxsidebar" role="navigation" aria-label="main navigation">
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<div class="sphinxsidebarwrapper">
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<h1 class="logo"><a href="index.html">esp-modem</a></h1>
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<h3>Navigation</h3>
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<ul class="current">
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<li class="toctree-l1 current"><a class="current reference internal" href="#">Brief intro</a><ul>
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<li class="toctree-l2"><a class="reference internal" href="#modem-components">Modem components</a><ul>
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<li class="toctree-l3"><a class="reference internal" href="#dce">DCE</a></li>
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<li class="toctree-l3"><a class="reference internal" href="#dte">DTE</a></li>
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<li class="toctree-l3"><a class="reference internal" href="#ppp-netif">PPP netif</a></li>
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<li class="toctree-l3"><a class="reference internal" href="#module">Module</a></li>
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</ul>
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</li>
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<li class="toctree-l2"><a class="reference internal" href="#use-cases">Use cases</a></li>
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<li class="toctree-l2"><a class="reference internal" href="#extensibility">Extensibility</a><ul>
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<li class="toctree-l3"><a class="reference internal" href="#cmux">CMUX</a></li>
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<li class="toctree-l3"><a class="reference internal" href="#dte-s">DTE’s</a></li>
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<li class="toctree-l3"><a class="reference internal" href="#other-devices">Other devices</a></li>
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</ul>
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</li>
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</ul>
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</li>
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<li class="toctree-l1"><a class="reference internal" href="api_docs.html">C interface</a></li>
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<li class="toctree-l1"><a class="reference internal" href="cxx_api_docs.html">C++ interface</a></li>
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<li class="toctree-l1"><a class="reference internal" href="advanced_api.html">Advanced use cases</a></li>
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<li class="toctree-l1"><a class="reference internal" href="internal_design.html">Internal design</a></li>
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<li class="toctree-l1"><a class="reference internal" href="internal_docs.html">Internal implementation</a></li>
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<h3>Related Topics</h3>
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<ul>
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<li><a href="index.html">Documentation overview</a><ul>
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<li>Previous: <a href="index.html" title="previous chapter">ESP-MODEM Programmers manual</a></li>
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<li>Next: <a href="api_docs.html" title="next chapter">C API Documentation</a></li>
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