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<!DOCTYPE html>
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<div class="section" id="rpi-monitor-lcd">
<h1>RPi-Monitor-LCD<a class="headerlink" href="#rpi-monitor-lcd" title="Permalink to this headline">¶</a></h1>
<p>This chapter is explaining how to use <strong>RPi-Monitor-LCD</strong> available in this
<a class="reference external" href="https://github.com/XavierBerger/RPi-Monitor-LCD">github repository</a></p>
<p>PCD8544 is a small and cheap LCD screen. We will see in this chapter how to use
it and connect it to <strong>RPi-Monitor</strong>.</p>
<div class="figure align-center">
<a class="reference internal image-reference" href="_images/lcd001.png"><img alt="_images/lcd001.png" src="_images/lcd001.png" style="width: 200px;" /></a>
</div>
<div class="section" id="lcd-connection">
<h2>LCD connection<a class="headerlink" href="#lcd-connection" title="Permalink to this headline">¶</a></h2>
<p>PCD8544 comes in two parts (the lcd screen and the pins) that need to be
soldered together. Once done, it can be installed in the breadboard as shown
in the drawing bellow:</p>
<div class="figure align-center" id="id1">
<a class="reference internal image-reference" href="_images/lcd002.png"><img alt="_images/lcd002.png" src="_images/lcd002.png" style="width: 400px;" /></a>
<p class="caption"><span class="caption-text">Schema made with Fritzing (fritzing.org)</span></p>
</div>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">If you want to reproduce this assembly, check carefully the pin order,
it may be different.</p>
</div>
</div>
<div class="section" id="preparation">
<h2>Preparation<a class="headerlink" href="#preparation" title="Permalink to this headline">¶</a></h2>
<p>My first goal is to test this new display. I look on the internet and find
different solution using Python or C. After few tries, I decided to use
Python based on the information shared into this post.</p>
<p>To use the PCD8544 display we need to install few software and load a
kernel module.</p>
<p>First, let’s install wiringpi2 from drogon.net</p>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">git</span> <span class="n">clone</span> <span class="n">git</span><span class="p">:</span><span class="o">//</span><span class="n">git</span><span class="o">.</span><span class="n">drogon</span><span class="o">.</span><span class="n">net</span><span class="o">/</span><span class="n">wiringPi</span>
<span class="n">cd</span> <span class="n">wiringPi</span>
<span class="o">./</span><span class="n">build</span>
</pre></div>
</div>
<p>Once wiringpi is installed, it is possible to test it with the following command:</p>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">gpio</span> <span class="n">readall</span>
</pre></div>
</div>
<table border="1" class="docutils">
<colgroup>
<col width="10%" />
<col width="13%" />
<col width="12%" />
<col width="8%" />
<col width="8%" />
<col width="0%" />
<col width="8%" />
<col width="8%" />
<col width="12%" />
<col width="13%" />
<col width="10%" />
</colgroup>
<thead valign="bottom">
<tr class="row-odd"><th class="head">wPi</th>
<th class="head">Name</th>
<th class="head">Mode</th>
<th class="head">Val</th>
<th class="head" colspan="3">Physical</th>
<th class="head">Val</th>
<th class="head">Mode</th>
<th class="head">Name</th>
<th class="head">wPi</th>
</tr>
</thead>
<tbody valign="top">
<tr class="row-even"><td> </td>
<td>3.3v</td>
<td> </td>
<td> </td>
<td>1</td>
<td> </td>
<td>2</td>
<td> </td>
<td> </td>
<td>5v</td>
<td> </td>
</tr>
<tr class="row-odd"><td>8</td>
<td>SDA</td>
<td>IN</td>
<td>Lo</td>
<td>3</td>
<td> </td>
<td>4</td>
<td> </td>
<td> </td>
<td>5V</td>
<td> </td>
</tr>
<tr class="row-even"><td>9</td>
<td>SCL</td>
<td>IN</td>
<td>Lo</td>
<td>5</td>
<td> </td>
<td>6</td>
<td> </td>
<td> </td>
<td>0v</td>
<td> </td>
</tr>
<tr class="row-odd"><td>7</td>
<td>GPIO7</td>
<td>IN</td>
<td>Lo</td>
<td>7</td>
<td> </td>
<td>8</td>
<td>Lo</td>
<td>ALT0</td>
<td>TxD</td>
<td>15</td>
</tr>
<tr class="row-even"><td> </td>
<td>0v</td>
<td> </td>
<td> </td>
<td>9</td>
<td> </td>
<td>10</td>
<td>Lo</td>
<td>ALT0</td>
<td>RxD</td>
<td>16</td>
</tr>
<tr class="row-odd"><td>0</td>
<td>GPIO0</td>
<td>IN</td>
<td>Hi</td>
<td>11</td>
<td> </td>
<td>12</td>
<td>Hi</td>
<td>OUT</td>
<td>GPIO1</td>
<td>1</td>
</tr>
<tr class="row-even"><td>2</td>
<td>GPIO2</td>
<td>IN</td>
<td>Lo</td>
<td>13</td>
<td> </td>
<td>14</td>
<td> </td>
<td> </td>
<td>0v</td>
<td> </td>
</tr>
<tr class="row-odd"><td>3</td>
<td>GPIO3</td>
<td>IN</td>
<td>Hi</td>
<td>15</td>
<td> </td>
<td>16</td>
<td>Lo</td>
<td>OUT</td>
<td>GPIO4</td>
<td>4</td>
</tr>
<tr class="row-even"><td> </td>
<td>3.3v</td>
<td> </td>
<td> </td>
<td>17</td>
<td> </td>
<td>18</td>
<td>Lo</td>
<td>OUT</td>
<td>GPIO5</td>
<td>5</td>
</tr>
<tr class="row-odd"><td>12</td>
<td>MOSI</td>
<td>ALT0</td>
<td>Hi</td>
<td>19</td>
<td> </td>
<td>20</td>
<td> </td>
<td> </td>
<td>0v</td>
<td> </td>
</tr>
<tr class="row-even"><td>13</td>
<td>MISO</td>
<td>ALT0</td>
<td>Hi</td>
<td>21</td>
<td> </td>
<td>22</td>
<td>Hi</td>
<td>IN</td>
<td>GPIO6</td>
<td>6</td>
</tr>
<tr class="row-odd"><td>14</td>
<td>SCLK</td>
<td>ALT0</td>
<td>Hi</td>
<td>23</td>
<td> </td>
<td>24</td>
<td>Lo</td>
<td>ALT0</td>
<td>CE1</td>
<td>10</td>
</tr>
<tr class="row-even"><td> </td>
<td>0v</td>
<td> </td>
<td> </td>
<td>25</td>
<td> </td>
<td>26</td>
<td>Lo</td>
<td>ALT0</td>
<td>CE1</td>
<td>11</td>
</tr>
</tbody>
</table>
<p>Now, install the python binding of wiringpi:</p>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">sudo</span> <span class="n">apt</span><span class="o">-</span><span class="n">get</span> <span class="n">install</span> <span class="n">python</span><span class="o">-</span><span class="n">dev</span> <span class="n">python</span><span class="o">-</span><span class="n">imaging</span> <span class="n">python</span><span class="o">-</span><span class="n">imaging</span><span class="o">-</span><span class="n">tk</span> <span class="n">python</span><span class="o">-</span><span class="n">pip</span>
<span class="n">sudo</span> <span class="n">pip</span> <span class="n">install</span> <span class="n">wiringpi2</span>
</pre></div>
</div>
<p>The program we will use require <code class="docutils literal"><span class="pre">spidev</span></code> to be activated. The kernel module
should then be activated.</p>
<p>To do so, comment the line blacklist <code class="docutils literal"><span class="pre">spi-bcm2708</span></code> by adding a heading <code class="docutils literal"><span class="pre">#</span></code>
in the file <code class="docutils literal"><span class="pre">/etc/modprobe.d/raspi-blacklist.conf</span></code> then reboot the
Raspberry Pi to activate this module.</p>
<p>Finally install <code class="docutils literal"><span class="pre">spidev</span></code> python library:</p>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">sudo</span> <span class="n">pip</span> <span class="n">install</span> <span class="n">spidev</span>
</pre></div>
</div>
<p>The prerequisite are now installed. In next chapter we will see how to install
the python library in charge of driving the PCD8544 LCD and how to use it.</p>
</div>
<div class="section" id="installation">
<h2>Installation<a class="headerlink" href="#installation" title="Permalink to this headline">¶</a></h2>
<p>Into Raspberry Pi forum, an interesting post catch my attention. I used it as
the base to control the LCD.</p>
<p>The library written Richard Hull’s is also interesting I then took this as a
example to create module that can be directly installed on the Raspberry Pi.</p>
<p>This pcd8544 library resulting is available into its own dedicated repository
in github.</p>
<p>To install it, execute the following commands:</p>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">git</span> <span class="n">clone</span> <span class="n">https</span><span class="p">:</span><span class="o">//</span><span class="n">github</span><span class="o">.</span><span class="n">com</span><span class="o">/</span><span class="n">XavierBerger</span><span class="o">/</span><span class="n">pcd8544</span><span class="o">.</span><span class="n">git</span>
<span class="n">cd</span> <span class="n">pcd8544</span>
<span class="o">./</span><span class="n">setup</span><span class="o">.</span><span class="n">py</span> <span class="n">clean</span> <span class="n">build</span>
<span class="n">sudo</span> <span class="o">./</span><span class="n">setup</span><span class="o">.</span><span class="n">py</span> <span class="n">install</span>
</pre></div>
</div>
<p>You can now test the installation with the proposed examples:</p>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">cd</span> <span class="n">examples</span>
<span class="o">./</span><span class="n">pi_logo</span><span class="o">.</span><span class="n">py</span>
</pre></div>
</div>
<p>If installation works properly, you should see the following screen:</p>
<div class="figure align-center">
<a class="reference internal image-reference" href="_images/lcd003.png"><img alt="_images/lcd003.png" src="_images/lcd003.png" style="width: 250px;" /></a>
</div>
<p>You can try to execute other examples to see what the library is capable to do with this LCD.</p>
</div>
<div class="section" id="usage">
<h2>Usage<a class="headerlink" href="#usage" title="Permalink to this headline">¶</a></h2>
<p>As I said in introduction, <strong>RPi-Monitor</strong> is gathering a lot of information and
some of them may be interesting to have without having to start a PC.
Information are made available from the embedded web server. To get and
display the information we then just have to create a web client and use
the library to display.</p>
<p>For people interesting about learning development I did comment my code:</p>
<div class="highlight-python"><div class="highlight"><pre><span></span><span class="ch">#!/usr/bin/env python</span>
<span class="kn">import</span> <span class="nn">httplib</span><span class="o">,</span> <span class="nn">time</span><span class="o">,</span> <span class="nn">os</span><span class="o">,</span> <span class="nn">sys</span><span class="o">,</span> <span class="nn">json</span>
<span class="kn">import</span> <span class="nn">pcd8544.lcd</span> <span class="kn">as</span> <span class="nn">lcd</span>
<span class="c1"># class Process dedicated to process data get from Client</span>
<span class="c1"># and send information to LCD and console</span>
<span class="k">class</span> <span class="nc">Process</span><span class="p">:</span>
<span class="c1"># Process constructor</span>
<span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="c1"># Initialize LCD</span>
<span class="n">lcd</span><span class="o">.</span><span class="n">init</span><span class="p">()</span>
<span class="c1"># Turn the backlight on</span>
<span class="n">lcd</span><span class="o">.</span><span class="n">backlight</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">run</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">jsonString</span><span class="p">):</span>
<span class="c1"># Parse data as json</span>
<span class="n">data</span> <span class="o">=</span> <span class="n">json</span><span class="o">.</span><span class="n">loads</span><span class="p">(</span> <span class="n">jsonString</span> <span class="p">)</span>
<span class="c1"># Try to get data from json or return default value</span>
<span class="k">try</span><span class="p">:</span>
<span class="n">rpi_temperature</span> <span class="o">=</span> <span class="n">data</span><span class="p">[</span><span class="s1">'living_room_temp'</span><span class="p">]</span>
<span class="k">except</span><span class="p">:</span>
<span class="n">rpi_temperature</span><span class="o">=</span><span class="s2">"--.---"</span>
<span class="k">try</span><span class="p">:</span>
<span class="n">rpi_humidity</span> <span class="o">=</span> <span class="n">data</span><span class="p">[</span><span class="s1">'humidity'</span><span class="p">]</span>
<span class="k">except</span><span class="p">:</span>
<span class="n">rpi_humidity</span> <span class="o">=</span> <span class="s2">"--"</span>
<span class="c1"># Construct string to be displayed on screens</span>
<span class="n">temperature</span> <span class="o">=</span> <span class="s2">"Temp: </span><span class="si">%s</span><span class="s2"> C"</span> <span class="o">%</span> <span class="n">rpi_temperature</span>
<span class="n">humidity</span> <span class="o">=</span> <span class="s2">"Humidity: </span><span class="si">%s</span><span class="s2"> </span><span class="si">%%</span><span class="s2">"</span> <span class="o">%</span> <span class="n">rpi_humidity</span>
<span class="n">lcd</span><span class="o">.</span><span class="n">gotorc</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">)</span>
<span class="n">lcd</span><span class="o">.</span><span class="n">text</span><span class="p">(</span><span class="s2">"RPi-Monitor"</span><span class="p">)</span>
<span class="n">lcd</span><span class="o">.</span><span class="n">gotorc</span><span class="p">(</span><span class="mi">2</span><span class="p">,</span><span class="mi">0</span><span class="p">)</span>
<span class="n">lcd</span><span class="o">.</span><span class="n">text</span><span class="p">(</span><span class="n">temperature</span><span class="p">)</span>
<span class="n">lcd</span><span class="o">.</span><span class="n">gotorc</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span><span class="mi">0</span><span class="p">)</span>
<span class="n">lcd</span><span class="o">.</span><span class="n">text</span><span class="p">(</span><span class="n">humidity</span><span class="p">)</span>
<span class="c1"># Also print string in console</span>
<span class="n">os</span><span class="o">.</span><span class="n">system</span><span class="p">(</span><span class="s2">"clear"</span><span class="p">)</span>
<span class="k">print</span> <span class="s2">" RPi-Monitor "</span>
<span class="k">print</span>
<span class="k">print</span> <span class="n">temperature</span>
<span class="k">print</span> <span class="n">humidity</span>
<span class="k">print</span>
<span class="n">time</span><span class="o">.</span><span class="n">sleep</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span>
<span class="c1"># Class client design to work as web client and get information</span>
<span class="c1"># from RPi-Monitor embedded web server</span>
<span class="k">class</span> <span class="nc">Client</span><span class="p">:</span>
<span class="c1"># Client constructor</span>
<span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="c1"># Create a Process object</span>
<span class="bp">self</span><span class="o">.</span><span class="n">process</span> <span class="o">=</span> <span class="n">Process</span><span class="p">()</span>
<span class="k">def</span> <span class="nf">run</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="c1"># Infinite loop</span>
<span class="k">while</span> <span class="bp">True</span><span class="p">:</span>
<span class="k">try</span><span class="p">:</span>
<span class="c1"># Initiate a connection to RPi-Monitor embedded server</span>
<span class="n">connection</span> <span class="o">=</span> <span class="n">httplib</span><span class="o">.</span><span class="n">HTTPConnection</span><span class="p">(</span><span class="s2">"localhost"</span><span class="p">,</span> <span class="mi">8888</span><span class="p">)</span>
<span class="c1"># Get the file dynamic.json</span>
<span class="n">connection</span><span class="o">.</span><span class="n">request</span><span class="p">(</span><span class="s2">"GET"</span><span class="p">,</span><span class="s2">"/dynamic.json"</span><span class="p">)</span>
<span class="c1"># Get the server response</span>
<span class="n">response</span> <span class="o">=</span> <span class="n">connection</span><span class="o">.</span><span class="n">getresponse</span><span class="p">()</span>
<span class="k">if</span> <span class="p">(</span> <span class="n">response</span><span class="o">.</span><span class="n">status</span> <span class="o">==</span> <span class="mi">200</span> <span class="p">):</span>
<span class="c1"># If response is OK, read data</span>
<span class="n">data</span> <span class="o">=</span> <span class="n">response</span><span class="o">.</span><span class="n">read</span><span class="p">()</span>
<span class="c1"># Run process object on extracted data</span>
<span class="bp">self</span><span class="o">.</span><span class="n">process</span><span class="o">.</span><span class="n">run</span><span class="p">(</span><span class="n">data</span><span class="p">)</span>
<span class="c1"># Close the connection to RPi-Monitor embedded server</span>
<span class="n">connection</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
<span class="k">finally</span><span class="p">:</span>
<span class="c1"># Wait 5 secondes before restarting the loop</span>
<span class="n">time</span><span class="o">.</span><span class="n">sleep</span><span class="p">(</span><span class="mi">5</span><span class="p">)</span>
<span class="c1"># Main function</span>
<span class="k">def</span> <span class="nf">main</span><span class="p">():</span>
<span class="k">try</span><span class="p">:</span>
<span class="c1"># Create a Client object</span>
<span class="n">client</span> <span class="o">=</span> <span class="n">Client</span><span class="p">()</span>
<span class="c1"># Run it</span>
<span class="n">client</span><span class="o">.</span><span class="n">run</span><span class="p">()</span>
<span class="k">except</span> <span class="ne">KeyboardInterrupt</span><span class="p">:</span>
<span class="c1"># if Ctrl+C has been pressed</span>
<span class="c1"># turn off the lcd backlight</span>
<span class="n">lcd</span><span class="o">.</span><span class="n">backlight</span><span class="p">(</span><span class="mi">0</span><span class="p">);</span>
<span class="c1"># exit from the program</span>
<span class="n">sys</span><span class="o">.</span><span class="n">exit</span><span class="p">(</span><span class="mi">0</span><span class="p">)</span>
<span class="c1"># Execute main if the script is directly called</span>
<span class="k">if</span> <span class="n">__name__</span> <span class="o">==</span> <span class="s2">"__main__"</span><span class="p">:</span>
<span class="n">main</span><span class="p">()</span>
</pre></div>
</div>
<p>This code is dedicated to extract the living room temperature and humidity
from <strong>RPi-Monitor</strong> information.</p>
<p>Copy this code into a file <code class="docutils literal"><span class="pre">rpimonitor-testlcd.py</span></code> the make this file
executable <code class="docutils literal"><span class="pre">chmod</span> <span class="pre">+x</span> <span class="pre">rpimonitor-testlcd.py</span></code> then execute <code class="docutils literal"><span class="pre">./rpimonitor-testlcd.py</span></code> it to see:</p>
<div class="figure align-center">
<a class="reference internal image-reference" href="_images/lcd004.png"><img alt="_images/lcd004.png" src="_images/lcd004.png" style="width: 250px;" /></a>
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Last updated on Mar 18, 2018.
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