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<h1 class="title indent">Report the temperature with ESP8266 to MQTT</h1>
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<time datetime="2015-10-11T12:10:00-07:00" pubdate data-updated="true"><i class="icon-calendar"></i> October 11, 2015</time>
<span class="byline author vcard"><i class='icon-user'></i> Paulus Schoutsen</span>
<span><i class='icon-time'></i> nine minutes reading time</span>
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<ul class="tags unstyled">
<li><a class='category' href='/blog/categories/esp8266/'>esp8266</a></li>
<li><a class='category' href='/blog/categories/how-to/'>how-to</a></li>
<li><a class='category' href='/blog/categories/mqtt/'>mqtt</a></li>
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<a class='comments'
href="#disqus_thread"
>Comments</a>
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</header>
<p>I recently learned about the ESP8266, a $5 chip that includes WiFi and is Arduino compatible. This means
that all your DIY projects can now be done for a fraction of the price.</p>
<p>For this tutorial, I&rsquo;ll walk through how to get going with ESP8266, get the temperature and humidity and
report it to MQTT where Home Asssistant can pick it up.</p>
<p class='img'>
<img src='/images/blog/2015-10-esp8266-temp/setup.png' />
Picture of the final setup (+ 2 LED for decoration)
</p>
<p class='img'>
<img src='/images/blog/2015-10-esp8266-temp/ha-sensor.png' />
Home Assistant will keep track of historical values and allow you to integrate it into automation.
</p>
<a name="read-more"></a>
<h3>Components</h3>
<p>I&rsquo;ve been using Adafruit for my shopping:</p>
<ul>
<li><a href="http://www.adafruit.com/product/2471">Adafruit HUZZAH ESP8266 Breakout</a> (<a href="https://learn.adafruit.com/adafruit-huzzah-esp8266-breakout/assembly">assembly instructions</a>)</li>
<li><a href="http://www.adafruit.com/product/2635">Adafruit HDC1008 Temperature &amp; Humidity Sensor Breakout Board</a> (<a href="https://learn.adafruit.com/adafruit-hdc1008-temperature-and-humidity-sensor-breakout/assembly">assembly instructions</a>)</li>
<li><a href="/components/mqtt.html#picking-a-broker">MQTT server</a></li>
</ul>
<p><em>Besides this, you will need the usual hardware prototype equipment: a breadboard, some wires,
soldering iron + wire, Serial USB cable.</em></p>
<h3>Connections</h3>
<p>On your breadboard, make the following connections from your ESP8266 to the HDC1008:</p>
<table>
<thead>
<tr>
<th> ESP8266 </th>
<th> HDC1008 </th>
</tr>
</thead>
<tbody>
<tr>
<td> GND </td>
<td> GND</td>
</tr>
<tr>
<td> 3V </td>
<td> Vin</td>
</tr>
<tr>
<td> 14 </td>
<td> SCL</td>
</tr>
<tr>
<td> #2 </td>
<td> SDA</td>
</tr>
</tbody>
</table>
<p><em>I picked <code>#2</code> and <code>14</code> myself, you can configure them in the sketch.</em></p>
<h3>Preparing your IDE</h3>
<p>Follow <a href="https://github.com/esp8266/Arduino#installing-with-boards-manager">these instructions</a> on how
to install and prepare the Arduino IDE for ESP8266 development.</p>
<p>After you&rsquo;re done installing, open the Arduino IDE, in the menu click on <code>sketch</code> -> <code>include library</code> ->
<code>manage libraries</code> and install the following libraries:</p>
<ul>
<li>PubSubClient by Nick &lsquo;O Leary</li>
<li>Adafruit HDC1000</li>
</ul>
<h3>Sketch</h3>
<p>If you have followed the previous steps, you&rsquo;re all set.</p>
<ul>
<li>Open Arduino IDE and create a new sketch (<code>File</code> -> <code>New</code>)</li>
<li>Copy and paste the below sketch to the Arduino IDE</li>
<li>Adjust the values line 6 - 14 to match your setup</li>
<li>Optional: If you want to connect to an MQTT server without a username or password, adjust line 63.</li>
<li>To have the ESP8266 accept our new sketch, we have to put it in upload mode. On the ESP8266 device
keep the GPIO0 button pressed while pressing the reset button. The red led will glow half bright to
indicate it is in upload mode.</li>
<li>Press the upload button in Arduino IDE</li>
<li>Open the serial monitor (<code>Tools</code> -> <code>Serial Monitor</code>) to see the output from your device</li>
</ul>
<p>This sketch will connect to your WiFi network and MQTT broker. It will read the temperature and humidity
from the sensor every second. It will report it to the MQTT server if the difference is > 1 since last
reported value. Reports to the MQTT broker are sent with retain set to <code>True</code>. This means that anyone
connecting to the MQTT topic will automatically be notified of the last reported value.</p>
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</pre></td><td class='code'><pre><code class='cpp'><span class='line'><span class="cp">#include &lt;ESP8266WiFi.h&gt;</span>
</span><span class='line'><span class="cp">#include &lt;Wire.h&gt;</span>
</span><span class='line'><span class="cp">#include &lt;PubSubClient.h&gt;</span>
</span><span class='line'><span class="cp">#include &lt;Adafruit_HDC1000.h&gt;</span>
</span><span class='line'>
</span><span class='line'><span class="cp">#define wifi_ssid &quot;YOUR WIFI SSID&quot;</span>
</span><span class='line'><span class="cp">#define wifi_password &quot;WIFI PASSWORD&quot;</span>
</span><span class='line'>
</span><span class='line'><span class="cp">#define mqtt_server &quot;YOUR_MQTT_SERVER_HOST&quot;</span>
</span><span class='line'><span class="cp">#define mqtt_user &quot;your_username&quot;</span>
</span><span class='line'><span class="cp">#define mqtt_password &quot;your_password&quot;</span>
</span><span class='line'>
</span><span class='line'><span class="cp">#define humidity_topic &quot;sensor/humidity&quot;</span>
</span><span class='line'><span class="cp">#define temperature_topic &quot;sensor/temperature&quot;</span>
</span><span class='line'>
</span><span class='line'><span class="n">WiFiClient</span> <span class="n">espClient</span><span class="p">;</span>
</span><span class='line'><span class="n">PubSubClient</span> <span class="nf">client</span><span class="p">(</span><span class="n">espClient</span><span class="p">);</span>
</span><span class='line'><span class="n">Adafruit_HDC1000</span> <span class="n">hdc</span> <span class="o">=</span> <span class="n">Adafruit_HDC1000</span><span class="p">();</span>
</span><span class='line'>
</span><span class='line'><span class="kt">void</span> <span class="nf">setup</span><span class="p">()</span> <span class="p">{</span>
</span><span class='line'> <span class="n">Serial</span><span class="p">.</span><span class="n">begin</span><span class="p">(</span><span class="mi">115200</span><span class="p">);</span>
</span><span class='line'> <span class="n">setup_wifi</span><span class="p">();</span>
</span><span class='line'> <span class="n">client</span><span class="p">.</span><span class="n">setServer</span><span class="p">(</span><span class="n">mqtt_server</span><span class="p">,</span> <span class="mi">1883</span><span class="p">);</span>
</span><span class='line'>
</span><span class='line'> <span class="c1">// Set SDA and SDL ports</span>
</span><span class='line'> <span class="n">Wire</span><span class="p">.</span><span class="n">begin</span><span class="p">(</span><span class="mi">2</span><span class="p">,</span> <span class="mi">14</span><span class="p">);</span>
</span><span class='line'>
</span><span class='line'> <span class="c1">// Start sensor</span>
</span><span class='line'> <span class="k">if</span> <span class="p">(</span><span class="o">!</span><span class="n">hdc</span><span class="p">.</span><span class="n">begin</span><span class="p">())</span> <span class="p">{</span>
</span><span class='line'> <span class="n">Serial</span><span class="p">.</span><span class="n">println</span><span class="p">(</span><span class="s">&quot;Couldn&#39;t find sensor!&quot;</span><span class="p">);</span>
</span><span class='line'> <span class="k">while</span> <span class="p">(</span><span class="mi">1</span><span class="p">);</span>
</span><span class='line'> <span class="p">}}</span>
</span><span class='line'>
</span><span class='line'><span class="kt">void</span> <span class="nf">setup_wifi</span><span class="p">()</span> <span class="p">{</span>
</span><span class='line'> <span class="n">delay</span><span class="p">(</span><span class="mi">10</span><span class="p">);</span>
</span><span class='line'> <span class="c1">// We start by connecting to a WiFi network</span>
</span><span class='line'> <span class="n">Serial</span><span class="p">.</span><span class="n">println</span><span class="p">();</span>
</span><span class='line'> <span class="n">Serial</span><span class="p">.</span><span class="n">print</span><span class="p">(</span><span class="s">&quot;Connecting to &quot;</span><span class="p">);</span>
</span><span class='line'> <span class="n">Serial</span><span class="p">.</span><span class="n">println</span><span class="p">(</span><span class="n">wifi_ssid</span><span class="p">);</span>
</span><span class='line'>
</span><span class='line'> <span class="n">WiFi</span><span class="p">.</span><span class="n">begin</span><span class="p">(</span><span class="n">wifi_ssid</span><span class="p">,</span> <span class="n">wifi_password</span><span class="p">);</span>
</span><span class='line'>
</span><span class='line'> <span class="k">while</span> <span class="p">(</span><span class="n">WiFi</span><span class="p">.</span><span class="n">status</span><span class="p">()</span> <span class="o">!=</span> <span class="n">WL_CONNECTED</span><span class="p">)</span> <span class="p">{</span>
</span><span class='line'> <span class="n">delay</span><span class="p">(</span><span class="mi">500</span><span class="p">);</span>
</span><span class='line'> <span class="n">Serial</span><span class="p">.</span><span class="n">print</span><span class="p">(</span><span class="s">&quot;.&quot;</span><span class="p">);</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'>
</span><span class='line'> <span class="n">Serial</span><span class="p">.</span><span class="n">println</span><span class="p">(</span><span class="s">&quot;&quot;</span><span class="p">);</span>
</span><span class='line'> <span class="n">Serial</span><span class="p">.</span><span class="n">println</span><span class="p">(</span><span class="s">&quot;WiFi connected&quot;</span><span class="p">);</span>
</span><span class='line'> <span class="n">Serial</span><span class="p">.</span><span class="n">println</span><span class="p">(</span><span class="s">&quot;IP address: &quot;</span><span class="p">);</span>
</span><span class='line'> <span class="n">Serial</span><span class="p">.</span><span class="n">println</span><span class="p">(</span><span class="n">WiFi</span><span class="p">.</span><span class="n">localIP</span><span class="p">());</span>
</span><span class='line'><span class="p">}</span>
</span><span class='line'>
</span><span class='line'><span class="kt">void</span> <span class="nf">reconnect</span><span class="p">()</span> <span class="p">{</span>
</span><span class='line'> <span class="c1">// Loop until we&#39;re reconnected</span>
</span><span class='line'> <span class="k">while</span> <span class="p">(</span><span class="o">!</span><span class="n">client</span><span class="p">.</span><span class="n">connected</span><span class="p">())</span> <span class="p">{</span>
</span><span class='line'> <span class="n">Serial</span><span class="p">.</span><span class="n">print</span><span class="p">(</span><span class="s">&quot;Attempting MQTT connection...&quot;</span><span class="p">);</span>
</span><span class='line'> <span class="c1">// Attempt to connect</span>
</span><span class='line'> <span class="c1">// If you do not want to use a username and password, change next line to</span>
</span><span class='line'> <span class="c1">// if (client.connect(&quot;ESP8266Client&quot;)) {</span>
</span><span class='line'> <span class="k">if</span> <span class="p">(</span><span class="n">client</span><span class="p">.</span><span class="n">connect</span><span class="p">(</span><span class="s">&quot;ESP8266Client&quot;</span><span class="p">,</span> <span class="n">mqtt_user</span><span class="p">,</span> <span class="n">mqtt_password</span><span class="p">))</span> <span class="p">{</span>
</span><span class='line'> <span class="n">Serial</span><span class="p">.</span><span class="n">println</span><span class="p">(</span><span class="s">&quot;connected&quot;</span><span class="p">);</span>
</span><span class='line'> <span class="p">}</span> <span class="k">else</span> <span class="p">{</span>
</span><span class='line'> <span class="n">Serial</span><span class="p">.</span><span class="n">print</span><span class="p">(</span><span class="s">&quot;failed, rc=&quot;</span><span class="p">);</span>
</span><span class='line'> <span class="n">Serial</span><span class="p">.</span><span class="n">print</span><span class="p">(</span><span class="n">client</span><span class="p">.</span><span class="n">state</span><span class="p">());</span>
</span><span class='line'> <span class="n">Serial</span><span class="p">.</span><span class="n">println</span><span class="p">(</span><span class="s">&quot; try again in 5 seconds&quot;</span><span class="p">);</span>
</span><span class='line'> <span class="c1">// Wait 5 seconds before retrying</span>
</span><span class='line'> <span class="n">delay</span><span class="p">(</span><span class="mi">5000</span><span class="p">);</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'><span class="p">}</span>
</span><span class='line'>
</span><span class='line'><span class="kt">bool</span> <span class="nf">checkBound</span><span class="p">(</span><span class="kt">float</span> <span class="n">newValue</span><span class="p">,</span> <span class="kt">float</span> <span class="n">prevValue</span><span class="p">,</span> <span class="kt">float</span> <span class="n">maxDiff</span><span class="p">)</span> <span class="p">{</span>
</span><span class='line'> <span class="k">return</span> <span class="n">newValue</span> <span class="o">&lt;</span> <span class="n">prevValue</span> <span class="o">-</span> <span class="n">maxDiff</span> <span class="o">||</span> <span class="n">newValue</span> <span class="o">&gt;</span> <span class="n">prevValue</span> <span class="o">+</span> <span class="n">maxDiff</span><span class="p">;</span>
</span><span class='line'><span class="p">}</span>
</span><span class='line'>
</span><span class='line'><span class="kt">long</span> <span class="n">lastMsg</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span>
</span><span class='line'><span class="kt">float</span> <span class="n">temp</span> <span class="o">=</span> <span class="mf">0.0</span><span class="p">;</span>
</span><span class='line'><span class="kt">float</span> <span class="n">hum</span> <span class="o">=</span> <span class="mf">0.0</span><span class="p">;</span>
</span><span class='line'><span class="kt">float</span> <span class="n">diff</span> <span class="o">=</span> <span class="mf">1.0</span><span class="p">;</span>
</span><span class='line'>
</span><span class='line'><span class="kt">void</span> <span class="nf">loop</span><span class="p">()</span> <span class="p">{</span>
</span><span class='line'> <span class="k">if</span> <span class="p">(</span><span class="o">!</span><span class="n">client</span><span class="p">.</span><span class="n">connected</span><span class="p">())</span> <span class="p">{</span>
</span><span class='line'> <span class="n">reconnect</span><span class="p">();</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'> <span class="n">client</span><span class="p">.</span><span class="n">loop</span><span class="p">();</span>
</span><span class='line'>
</span><span class='line'> <span class="kt">long</span> <span class="n">now</span> <span class="o">=</span> <span class="n">millis</span><span class="p">();</span>
</span><span class='line'> <span class="k">if</span> <span class="p">(</span><span class="n">now</span> <span class="o">-</span> <span class="n">lastMsg</span> <span class="o">&gt;</span> <span class="mi">1000</span><span class="p">)</span> <span class="p">{</span>
</span><span class='line'> <span class="n">lastMsg</span> <span class="o">=</span> <span class="n">now</span><span class="p">;</span>
</span><span class='line'>
</span><span class='line'> <span class="kt">float</span> <span class="n">newTemp</span> <span class="o">=</span> <span class="n">hdc</span><span class="p">.</span><span class="n">readTemperature</span><span class="p">();</span>
</span><span class='line'> <span class="kt">float</span> <span class="n">newHum</span> <span class="o">=</span> <span class="n">hdc</span><span class="p">.</span><span class="n">readHumidity</span><span class="p">();</span>
</span><span class='line'>
</span><span class='line'> <span class="k">if</span> <span class="p">(</span><span class="n">checkBound</span><span class="p">(</span><span class="n">newTemp</span><span class="p">,</span> <span class="n">temp</span><span class="p">,</span> <span class="n">diff</span><span class="p">))</span> <span class="p">{</span>
</span><span class='line'> <span class="n">temp</span> <span class="o">=</span> <span class="n">newTemp</span><span class="p">;</span>
</span><span class='line'> <span class="n">Serial</span><span class="p">.</span><span class="n">print</span><span class="p">(</span><span class="s">&quot;New temperature:&quot;</span><span class="p">);</span>
</span><span class='line'> <span class="n">Serial</span><span class="p">.</span><span class="n">println</span><span class="p">(</span><span class="n">String</span><span class="p">(</span><span class="n">temp</span><span class="p">).</span><span class="n">c_str</span><span class="p">());</span>
</span><span class='line'> <span class="n">client</span><span class="p">.</span><span class="n">publish</span><span class="p">(</span><span class="n">temperature_topic</span><span class="p">,</span> <span class="n">String</span><span class="p">(</span><span class="n">temp</span><span class="p">).</span><span class="n">c_str</span><span class="p">(),</span> <span class="nb">true</span><span class="p">);</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'>
</span><span class='line'> <span class="k">if</span> <span class="p">(</span><span class="n">checkBound</span><span class="p">(</span><span class="n">newHum</span><span class="p">,</span> <span class="n">hum</span><span class="p">,</span> <span class="n">diff</span><span class="p">))</span> <span class="p">{</span>
</span><span class='line'> <span class="n">hum</span> <span class="o">=</span> <span class="n">newHum</span><span class="p">;</span>
</span><span class='line'> <span class="n">Serial</span><span class="p">.</span><span class="n">print</span><span class="p">(</span><span class="s">&quot;New humidity:&quot;</span><span class="p">);</span>
</span><span class='line'> <span class="n">Serial</span><span class="p">.</span><span class="n">println</span><span class="p">(</span><span class="n">String</span><span class="p">(</span><span class="n">hum</span><span class="p">).</span><span class="n">c_str</span><span class="p">());</span>
</span><span class='line'> <span class="n">client</span><span class="p">.</span><span class="n">publish</span><span class="p">(</span><span class="n">humidity_topic</span><span class="p">,</span> <span class="n">String</span><span class="p">(</span><span class="n">hum</span><span class="p">).</span><span class="n">c_str</span><span class="p">(),</span> <span class="nb">true</span><span class="p">);</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'><span class="p">}</span>
</span></code></pre></td></tr></table></div></figure>
<h3>Configuring Home Assistant</h3>
<p>The last step is to integrate the sensor values into Home Assistant. This can be done by setting up
Home Assistant to connect to the MQTT broker and subscribe to the sensor topics.</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
<span class='line-number'>15</span>
<span class='line-number'>16</span>
<span class='line-number'>17</span>
<span class='line-number'>18</span>
</pre></td><td class='code'><pre><code class='yaml'><span class='line'><span class="l-Scalar-Plain">mqtt</span><span class="p-Indicator">:</span>
</span><span class='line'> <span class="l-Scalar-Plain">broker</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain">YOUR_MQTT_SERVER_HOST</span>
</span><span class='line'> <span class="l-Scalar-Plain">username</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain">your_username</span>
</span><span class='line'> <span class="l-Scalar-Plain">password</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain">your_password</span>
</span><span class='line'>
</span><span class='line'><span class="l-Scalar-Plain">sensor</span><span class="p-Indicator">:</span>
</span><span class='line'> <span class="l-Scalar-Plain">platform</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain">mqtt</span>
</span><span class='line'> <span class="l-Scalar-Plain">name</span><span class="p-Indicator">:</span> <span class="s">&quot;Temperature&quot;</span>
</span><span class='line'> <span class="l-Scalar-Plain">state_topic</span><span class="p-Indicator">:</span> <span class="s">&quot;sensor/temperature&quot;</span>
</span><span class='line'> <span class="l-Scalar-Plain">qos</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain">0</span>
</span><span class='line'> <span class="l-Scalar-Plain">unit_of_measurement</span><span class="p-Indicator">:</span> <span class="s">&quot;ºC&quot;</span>
</span><span class='line'>
</span><span class='line'><span class="l-Scalar-Plain">sensor 2</span><span class="p-Indicator">:</span>
</span><span class='line'> <span class="l-Scalar-Plain">platform</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain">mqtt</span>
</span><span class='line'> <span class="l-Scalar-Plain">name</span><span class="p-Indicator">:</span> <span class="s">&quot;Humidity&quot;</span>
</span><span class='line'> <span class="l-Scalar-Plain">state_topic</span><span class="p-Indicator">:</span> <span class="s">&quot;sensor/humidity&quot;</span>
</span><span class='line'> <span class="l-Scalar-Plain">qos</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain">0</span>
</span><span class='line'> <span class="l-Scalar-Plain">unit_of_measurement</span><span class="p-Indicator">:</span> <span class="s">&quot;%&quot;</span>
</span></code></pre></td></tr></table></div></figure>
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