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<h2 id="air-quality-sensor-project-via-bluetooth">Air quality sensor project via Bluetooth</h2>
<p>This is a follow-on project to the <a href="../air_quality_sensor/">Basic Air Quality Sensor</a> project; so it is
assumed that you have worked through that project and have your CO<sub>2</sub> sensor working properly with
your Arduino Primo board. </p>
<p>So let's get started making this thing Bluetooth enabled!</p>
<h3 id="add-bluetooth-gatt-services">Add Bluetooth GATT Services</h3>
<p>Since we already built the previous demo on the <a href="../bleprph/bleprph-app/">bluetooth peripheral</a> basic
app most of the bluetooth plumbing has already been taken care of for us. What's left is for us
to add the required GATT services for advertising the Carbon Dioxide sensor so that
other devices can get those values.</p>
<p>First, we'll define the GATT Services in <code>apps/air_quality/src/bleprph.h</code>.</p>
<div class="codehilite" style="background: #ffffff"><pre style="line-height: 125%;"><span></span><code><span style="color: #177500">/* Sensor Data */</span>
<span style="color: #177500">/* e761d2af-1c15-4fa7-af80-b5729002b340 */</span>
<span style="color: #A90D91">static</span> <span style="color: #A90D91">const</span> <span style="color: #000000">ble_uuid128_t</span> <span style="color: #000000">gatt_svr_svc_co2_uuid</span> <span style="color: #000000">=</span>
<span style="color: #000000">BLE_UUID128_INIT</span>(<span style="color: #1C01CE">0x40</span>, <span style="color: #1C01CE">0xb3</span>, <span style="color: #1C01CE">0x20</span>, <span style="color: #1C01CE">0x90</span>, <span style="color: #1C01CE">0x72</span>, <span style="color: #1C01CE">0xb5</span>, <span style="color: #1C01CE">0x80</span>, <span style="color: #1C01CE">0xaf</span>,
<span style="color: #1C01CE">0xa7</span>, <span style="color: #1C01CE">0x4f</span>, <span style="color: #1C01CE">0x15</span>, <span style="color: #1C01CE">0x1c</span>, <span style="color: #1C01CE">0xaf</span>, <span style="color: #1C01CE">0xd2</span>, <span style="color: #1C01CE">0x61</span>, <span style="color: #1C01CE">0xe7</span>);
<span style="color: #633820">#define CO2_SNS_TYPE 0xDEAD</span>
<span style="color: #633820">#define CO2_SNS_STRING &quot;SenseAir K30 CO2 Sensor&quot;</span>
<span style="color: #633820">#define CO2_SNS_VAL 0xBEAD</span>
<span style="color: #A90D91">uint16_t</span> <span style="color: #000000">gatt_co2_val</span>;
</code></pre></div>
<p>You can use any hex values you choose for the sensor type and sensor values, and you can
even forget the sensor type and sensor string definitions altogether but they make
the results look nice in our Bluetooth App for Mac OS X and iOS.</p>
<p>Next we'll add those services to <code>apps/air_quality/src/gatt_svr.c</code>.</p>
<div class="codehilite" style="background: #ffffff"><pre style="line-height: 125%;"><span></span><code><span style="color: #A90D91">static</span> <span style="color: #A90D91">int</span>
<span style="color: #000000">gatt_svr_sns_access</span>(<span style="color: #A90D91">uint16_t</span> <span style="color: #000000">conn_handle</span>, <span style="color: #A90D91">uint16_t</span> <span style="color: #000000">attr_handle</span>,
<span style="color: #A90D91">struct</span> <span style="color: #3F6E75">ble_gatt_access_ctxt</span> <span style="color: #000000">*ctxt</span>,
<span style="color: #A90D91">void</span> <span style="color: #000000">*arg</span>);
<span style="color: #A90D91">static</span> <span style="color: #A90D91">uint16_t</span> <span style="color: #000000">gatt_co2_val_len</span>;
</code></pre></div>
<p>Make sure it is added as <em>primary</em> service.</p>
<div class="codehilite" style="background: #ffffff"><pre style="line-height: 125%;"><span></span><code><span style="color: #A90D91">static</span> <span style="color: #A90D91">const</span> <span style="color: #A90D91">struct</span> <span style="color: #3F6E75">ble_gatt_svc_def</span> <span style="color: #000000">gatt_svr_svcs</span>[] <span style="color: #000000">=</span> {
{
<span style="color: #177500">/*** Service: Security test. */</span>
.<span style="color: #000000">type</span> <span style="color: #000000">=</span> <span style="color: #000000">BLE_GATT_SVC_TYPE_PRIMARY</span>,
.<span style="color: #000000">uuid</span> <span style="color: #000000">=</span> <span style="color: #000000">&amp;gatt_svr_svc_sec_test_uuid</span>.<span style="color: #000000">u</span>,
.<span style="color: #000000">characteristics</span> <span style="color: #000000">=</span> (<span style="color: #A90D91">struct</span> <span style="color: #3F6E75">ble_gatt_chr_def</span>[]) { {
<span style="color: #177500">/*** Characteristic: Random number generator. */</span>
.<span style="color: #000000">uuid</span> <span style="color: #000000">=</span> <span style="color: #000000">&amp;gatt_svr_chr_sec_test_rand_uuid</span>.<span style="color: #000000">u</span>,
.<span style="color: #000000">access_cb</span> <span style="color: #000000">=</span> <span style="color: #000000">gatt_svr_chr_access_sec_test</span>,
.<span style="color: #000000">flags</span> <span style="color: #000000">=</span> <span style="color: #000000">BLE_GATT_CHR_F_READ</span> <span style="color: #000000">|</span> <span style="color: #000000">BLE_GATT_CHR_F_READ_ENC</span>,
}, {
<span style="color: #177500">/*** Characteristic: Static value. */</span>
.<span style="color: #000000">uuid</span> <span style="color: #000000">=</span> <span style="color: #000000">&amp;gatt_svr_chr_sec_test_static_uuid</span>,.<span style="color: #000000">u</span>
.<span style="color: #000000">access_cb</span> <span style="color: #000000">=</span> <span style="color: #000000">gatt_svr_chr_access_sec_test</span>,
.<span style="color: #000000">flags</span> <span style="color: #000000">=</span> <span style="color: #000000">BLE_GATT_CHR_F_READ</span> <span style="color: #000000">|</span>
<span style="color: #000000">BLE_GATT_CHR_F_WRITE</span> <span style="color: #000000">|</span> <span style="color: #000000">BLE_GATT_CHR_F_WRITE_ENC</span>,
}, {
<span style="color: #1C01CE">0</span>, <span style="color: #177500">/* No more characteristics in this service. */</span>
} },
},
{
<span style="color: #177500">/*** CO2 Level Notification Service. */</span>
.<span style="color: #000000">type</span> <span style="color: #000000">=</span> <span style="color: #000000">BLE_GATT_SVC_TYPE_PRIMARY</span>,
.<span style="color: #000000">uuid</span> <span style="color: #000000">=</span> <span style="color: #000000">&amp;gatt_svr_svc_co2_uuid</span>.<span style="color: #000000">u</span>,
.<span style="color: #000000">characteristics</span> <span style="color: #000000">=</span> (<span style="color: #A90D91">struct</span> <span style="color: #3F6E75">ble_gatt_chr_def</span>[]) { {
.<span style="color: #000000">uuid</span> <span style="color: #000000">=</span> <span style="color: #000000">BLE_UUID16_DECLARE</span>(<span style="color: #000000">CO2_SNS_TYPE</span>),
.<span style="color: #000000">access_cb</span> <span style="color: #000000">=</span> <span style="color: #000000">gatt_svr_sns_access</span>,
.<span style="color: #000000">flags</span> <span style="color: #000000">=</span> <span style="color: #000000">BLE_GATT_CHR_F_READ</span>,
}, {
.<span style="color: #000000">uuid</span> <span style="color: #000000">=</span> <span style="color: #000000">BLE_UUID16_DECLARE</span>(<span style="color: #000000">CO2_SNS_VAL</span>),
.<span style="color: #000000">access_cb</span> <span style="color: #000000">=</span> <span style="color: #000000">gatt_svr_sns_access</span>,
.<span style="color: #000000">flags</span> <span style="color: #000000">=</span> <span style="color: #000000">BLE_GATT_CHR_F_NOTIFY</span>,
}, {
<span style="color: #1C01CE">0</span>, <span style="color: #177500">/* No more characteristics in this service. */</span>
} },
},
{
<span style="color: #1C01CE">0</span>, <span style="color: #177500">/* No more services. */</span>
},
};
</code></pre></div>
<p>Next we need to tell the GATT Server how to handle requests for CO<sub>2</sub> readings :</p>
<div class="codehilite" style="background: #ffffff"><pre style="line-height: 125%;"><span></span><code><span style="color: #000000">sstatic</span> <span style="color: #A90D91">int</span>
<span style="color: #000000">gatt_svr_sns_access</span>(<span style="color: #A90D91">uint16_t</span> <span style="color: #000000">conn_handle</span>, <span style="color: #A90D91">uint16_t</span> <span style="color: #000000">attr_handle</span>,
<span style="color: #A90D91">struct</span> <span style="color: #3F6E75">ble_gatt_access_ctxt</span> <span style="color: #000000">*ctxt</span>,
<span style="color: #A90D91">void</span> <span style="color: #000000">*arg</span>)
{
<span style="color: #A90D91">uint16_t</span> <span style="color: #000000">uuid16</span>;
<span style="color: #A90D91">int</span> <span style="color: #000000">rc</span>;
<span style="color: #000000">uuid16</span> <span style="color: #000000">=</span> <span style="color: #000000">ble_uuid_u16</span>(<span style="color: #000000">ctxt-&gt;chr-&gt;uuid</span>);
<span style="color: #A90D91">switch</span> (<span style="color: #000000">uuid16</span>) {
<span style="color: #A90D91">case</span> <span style="color: #000000">CO2_SNS_TYPE</span>:
<span style="color: #000000">assert</span>(<span style="color: #000000">ctxt-&gt;op</span> <span style="color: #000000">==</span> <span style="color: #000000">BLE_GATT_ACCESS_OP_READ_CHR</span>);
<span style="color: #000000">rc</span> <span style="color: #000000">=</span> <span style="color: #000000">os_mbuf_append</span>(<span style="color: #000000">ctxt-&gt;om</span>, <span style="color: #000000">CO2_SNS_STRING</span>, <span style="color: #A90D91">sizeof</span> <span style="color: #000000">CO2_SNS_STRING</span>);
<span style="color: #000000">BLEPRPH_LOG</span>(<span style="color: #000000">INFO</span>, <span style="color: #C41A16">&quot;CO2 SENSOR TYPE READ: %s\n&quot;</span>, <span style="color: #000000">CO2_SNS_STRING</span>);
<span style="color: #A90D91">return</span> <span style="color: #000000">rc</span> <span style="color: #000000">==</span> <span style="color: #1C01CE">0</span> <span style="color: #000000">?</span> <span style="color: #1C01CE">0</span> <span style="color: #000000">:</span> <span style="color: #000000">BLE_ATT_ERR_INSUFFICIENT_RES</span>;
<span style="color: #A90D91">case</span> <span style="color: #000000">CO2_SNS_VAL</span>:
<span style="color: #A90D91">if</span> (<span style="color: #000000">ctxt-&gt;op</span> <span style="color: #000000">==</span> <span style="color: #000000">BLE_GATT_ACCESS_OP_WRITE_CHR</span>) {
<span style="color: #000000">rc</span> <span style="color: #000000">=</span> <span style="color: #000000">gatt_svr_chr_write</span>(<span style="color: #000000">ctxt-&gt;om</span>, <span style="color: #1C01CE">0</span>,
<span style="color: #A90D91">sizeof</span> <span style="color: #000000">gatt_co2_val</span>,
<span style="color: #000000">&amp;gatt_co2_val</span>,
<span style="color: #000000">&amp;gatt_co2_val_len</span>);
<span style="color: #A90D91">return</span> <span style="color: #000000">rc</span>;
} <span style="color: #A90D91">else</span> <span style="color: #A90D91">if</span> (<span style="color: #000000">ctxt-&gt;op</span> <span style="color: #000000">==</span> <span style="color: #000000">BLE_GATT_ACCESS_OP_READ_CHR</span>) {
<span style="color: #000000">rc</span> <span style="color: #000000">=</span> <span style="color: #000000">os_mbuf_append</span>(<span style="color: #000000">ctxt-&gt;om</span>, <span style="color: #000000">&amp;gatt_co2_val</span>,
<span style="color: #A90D91">sizeof</span> <span style="color: #000000">gatt_co2_val</span>);
<span style="color: #A90D91">return</span> <span style="color: #000000">rc</span> <span style="color: #000000">==</span> <span style="color: #1C01CE">0</span> <span style="color: #000000">?</span> <span style="color: #1C01CE">0</span> <span style="color: #000000">:</span> <span style="color: #000000">BLE_ATT_ERR_INSUFFICIENT_RES</span>;
}
<span style="color: #A90D91">default</span><span style="color: #000000">:</span>
<span style="color: #000000">assert</span>(<span style="color: #1C01CE">0</span>);
<span style="color: #A90D91">return</span> <span style="color: #000000">BLE_ATT_ERR_UNLIKELY</span>;
}
}
</code></pre></div>
<p>Now it's time to go into our <code>apps/air_quality/src/main.c</code> and change how we read CO<sub>2</sub> readings and
respond to requests. </p>
<p>We'll need a task handler with an event queue for the CO<sub>2</sub> readings -- they were handled by the shell task in the previous tutorial but now it needs to be replaced by a different handler as shown below.</p>
<div class="codehilite" style="background: #ffffff"><pre style="line-height: 125%;"><span></span><code><span style="color: #177500">/* CO2 Task settings */</span>
<span style="color: #633820">#define CO2_TASK_PRIO 5</span>
<span style="color: #633820">#define CO2_STACK_SIZE (OS_STACK_ALIGN(336))</span>
<span style="color: #A90D91">struct</span> <span style="color: #3F6E75">os_eventq</span> <span style="color: #000000">co2_evq</span>;
<span style="color: #A90D91">struct</span> <span style="color: #3F6E75">os_task</span> <span style="color: #000000">co2_task</span>;
<span style="color: #000000">bssnz_t</span> <span style="color: #000000">os_stack_t</span> <span style="color: #000000">co2_stack</span>[<span style="color: #000000">CO2_STACK_SIZE</span>];
</code></pre></div>
<p>And of course we'll need to go to our <code>main()</code> and do all the standard task and event setup we
normally do by adding the following. Again, remember to delete all the shell event queues and tasks.</p>
<div class="codehilite" style="background: #ffffff"><pre style="line-height: 125%;"><span></span><code><span style="color: #177500">/* Initialize sensor eventq */</span>
<span style="color: #000000">os_eventq_init</span>(<span style="color: #000000">&amp;co2_evq</span>);
<span style="color: #177500">/* Create the CO2 reader task. </span>
<span style="color: #177500"> * All sensor reading operations are performed in this task.</span>
<span style="color: #177500"> */</span>
<span style="color: #000000">os_task_init</span>(<span style="color: #000000">&amp;co2_task</span>, <span style="color: #C41A16">&quot;sensor&quot;</span>, <span style="color: #000000">co2_task_handler</span>,
<span style="color: #A90D91">NULL</span>, <span style="color: #000000">CO2_TASK_PRIO</span>, <span style="color: #000000">OS_WAIT_FOREVER</span>,
<span style="color: #000000">co2_stack</span>, <span style="color: #000000">CO2_STACK_SIZE</span>);
</code></pre></div>
<p>We'll also need to add a task handler -- since we initialized it above:</p>
<div class="codehilite" style="background: #ffffff"><pre style="line-height: 125%;"><span></span><code><span style="color: #177500">/**</span>
<span style="color: #177500"> * Event loop for the sensor task.</span>
<span style="color: #177500"> */</span>
<span style="color: #A90D91">static</span> <span style="color: #A90D91">void</span>
<span style="color: #000000">co2_task_handler</span>(<span style="color: #A90D91">void</span> <span style="color: #000000">*unused</span>)
{
<span style="color: #A90D91">while</span> (<span style="color: #1C01CE">1</span>) {
<span style="color: #000000">co2_read_event</span>();
<span style="color: #177500">/* Wait 2 second */</span>
<span style="color: #000000">os_time_delay</span>(<span style="color: #000000">OS_TICKS_PER_SEC</span> <span style="color: #000000">*</span> <span style="color: #1C01CE">2</span>);
}
}
</code></pre></div>
<p>And finally, we'll take care of that <code>co2_read_event()</code> function:</p>
<div class="codehilite" style="background: #ffffff"><pre style="line-height: 125%;"><span></span><code><span style="color: #A90D91">int</span>
<span style="color: #000000">co2_read_event</span>(<span style="color: #A90D91">void</span>)
{
<span style="color: #A90D91">int</span> <span style="color: #000000">value</span>;
<span style="color: #A90D91">enum</span> <span style="color: #000000">senseair_read_type</span> <span style="color: #000000">type</span> <span style="color: #000000">=</span> <span style="color: #000000">SENSEAIR_CO2</span>;
<span style="color: #A90D91">uint16_t</span> <span style="color: #000000">chr_val_handle</span>;
<span style="color: #A90D91">int</span> <span style="color: #000000">rc</span>;
<span style="color: #000000">value</span> <span style="color: #000000">=</span> <span style="color: #000000">senseair_read</span>(<span style="color: #000000">type</span>);
<span style="color: #A90D91">if</span> (<span style="color: #000000">value</span> <span style="color: #000000">&gt;=</span> <span style="color: #1C01CE">0</span>) {
<span style="color: #000000">console_printf</span>(<span style="color: #C41A16">&quot;Got %d\n&quot;</span>, <span style="color: #000000">value</span>);
} <span style="color: #A90D91">else</span> {
<span style="color: #000000">console_printf</span>(<span style="color: #C41A16">&quot;Error while reading: %d\n&quot;</span>, <span style="color: #000000">value</span>);
<span style="color: #A90D91">goto</span> <span style="color: #000000">err</span>;
}
<span style="color: #000000">gatt_co2_val</span> <span style="color: #000000">=</span> <span style="color: #000000">value</span>;
<span style="color: #000000">rc</span> <span style="color: #000000">=</span> <span style="color: #000000">ble_gatts_find_chr</span>(<span style="color: #000000">&amp;gatt_svr_svc_co2_uuid</span>.<span style="color: #000000">u</span>, <span style="color: #000000">BLE_UUID16_DECLARE</span>(<span style="color: #000000">CO2_SNS_VAL</span>), <span style="color: #A90D91">NULL</span>, <span style="color: #000000">&amp;chr_val_handle</span>);
<span style="color: #000000">assert</span>(<span style="color: #000000">rc</span> <span style="color: #000000">==</span> <span style="color: #1C01CE">0</span>);
<span style="color: #000000">ble_gatts_chr_updated</span>(<span style="color: #000000">chr_val_handle</span>);
<span style="color: #A90D91">return</span> (<span style="color: #1C01CE">0</span>);
<span style="color: #000000">err</span>:
<span style="color: #A90D91">return</span> (<span style="color: #000000">rc</span>);
}
</code></pre></div>
<p>You'll notice that it looks eeirily similar to a portion of the shell event we created
earlier. This one simply reads and updates the CO<sub>2</sub> value and sends that over BLE to any
connected clients instead. </p>
<p>We can now build, create-image and load the app onto our Arduino Primo board, and then
connect and see the updated values! The image below shows the results using MyNewt Sensor Reader,
a Mac OS X app developed for connecting to MyNewt devices over Bluetooth but you can also use LightBlue
or any other application that can connect to, and read, Bluetooth data.</p>
<p><img alt="MyNewt Sensor Reader" src="../pics/MyNewtSensorReader.jpg" /></p>
<p>Congratulations!!</p>
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