blog/archive/2023/01/01.rss

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   4                 <title>Petter Reinholdtsen - Entries from January 2023</title>
   5                 <description>Entries from January 2023</description>
   6                 <link>https://people.skolelinux.org/pere/blog/</link>
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   8
   9         <item>
  10                 <title>LinuxCNC MQTT publisher component</title>
  11                 <link>https://people.skolelinux.org/pere/blog/LinuxCNC_MQTT_publisher_component.html</link>
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  13                 <pubDate>Sun, 8 Jan 2023 19:30:00 +0100</pubDate>
  14                 <description>&lt;p&gt;I watched &lt;a href=&quot;https://yewtu.be/watch?v=jmKUV3aNLjk&quot;&gt;a 2015
  15 video from Andreas Schiffler&lt;/a&gt; the other day, where he set up
  16 &lt;a href=&quot;https://linuxcnc.org/&quot;&gt;LinuxCNC&lt;/a&gt; to send status
  17 information to the MQTT broker IBM Bluemix.  As I also use MQTT for
  18 graphing, it occured to me that a generic MQTT LinuxCNC component
  19 would be useful and I set out to implement it.  Today I got the first
  20 draft limping along and submitted as
  21 &lt;a href=&quot;https://github.com/LinuxCNC/linuxcnc/pull/2253&quot;&gt;a patch to the
  22 LinuxCNC project&lt;/a&gt;.&lt;/p&gt;
  23
  24 &lt;p&gt;The simple part was setting up the MQTT publishing code in Python.
  25 I already have set up other parts submitting data to my Mosquito MQTT
  26 broker, so I could reuse that code.  Writing a LinuxCNC component in
  27 Python as new to me, but using existing examples in the code
  28 repository and the extensive documentation, this was fairly straight
  29 forward.  The hardest part was creating a automated test for the
  30 component to ensure it was working.  Testing it in a simulated
  31 LinuxCNC machine proved very useful, as I discovered features I needed
  32 that I had not thought of yet, and adjusted the code quite a bit to
  33 make it easier to test without a operational MQTT broker
  34 available.&lt;/p&gt;
  35
  36 &lt;p&gt;The draft is ready and working, but I am unsure which LinuxCNC HAL
  37 pins I should collect and publish by default (in other words, the
  38 default set of information pieces published), and how to get the
  39 machine name from the LinuxCNC INI file.  The latter is a minor
  40 detail, but I expect it would be useful in a setup with several
  41 machines available.  I am hoping for feedback from the experienced
  42 LinuxCNC developers and users, to make the component even better
  43 before it can go into the mainland LinuxCNC code base.&lt;/p&gt;
  44
  45 &lt;p&gt;Since I started on the MQTT component, I came across
  46 &lt;a href=&quot;https://yewtu.be/watch?v=Bqa2grG0XtA&quot;&gt;another video from Kent
  47 VanderVelden&lt;/a&gt; where he combine LinuxCNC with a set of screen glasses
  48 controlled by a Raspberry Pi, and it occured to me that it would
  49 be useful for such use cases if LinuxCNC also provided a REST API for
  50 querying its status.  I hope to start on such component once the MQTT
  51 component is working well.&lt;/p&gt;
  52
  53 &lt;p&gt;As usual, if you use Bitcoin and want to show your support of my
  54 activities, please send Bitcoin donations to my address
  55 &lt;b&gt;&lt;a href=&quot;bitcoin:15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b&quot;&gt;15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b&lt;/a&gt;&lt;/b&gt;.&lt;/p&gt;
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