blog/data/2023-01-08-linuxcnc-mqtt.txt

   1 Title: LinuxCNC MQTT publisher component
   2 Tags: english, debian, linuxcnc, robot
   3 Date: 2023-01-08 19:30
   4
   5 <p>I watched <a href="https://yewtu.be/watch?v=jmKUV3aNLjk">a 2015
   6 video from Andreas Schiffler</a> the other day, where he set up
   7 <a href="https://linuxcnc.org/">LinuxCNC</a> to send status
   8 information to the MQTT broker IBM Bluemix.  As I also use MQTT for
   9 graphing, it occured to me that a generic MQTT LinuxCNC component
  10 would be useful and I set out to implement it.  Today I got the first
  11 draft limping along and submitted as
  12 <a href="https://github.com/LinuxCNC/linuxcnc/pull/2253">a patch to the
  13 LinuxCNC project</a>.</p>
  14
  15 <p>The simple part was setting up the MQTT publishing code in Python.
  16 I already have set up other parts submitting data to my Mosquito MQTT
  17 broker, so I could reuse that code.  Writing a LinuxCNC component in
  18 Python as new to me, but using existing examples in the code
  19 repository and the extensive documentation, this was fairly straight
  20 forward.  The hardest part was creating a automated test for the
  21 component to ensure it was working.  Testing it in a simulated
  22 LinuxCNC machine proved very useful, as I discovered features I needed
  23 that I had not thought of yet, and adjusted the code quite a bit to
  24 make it easier to test without a operational MQTT broker
  25 available.</p>
  26
  27 <p>The draft is ready and working, but I am unsure which LinuxCNC HAL
  28 pins I should collect and publish by default (in other words, the
  29 default set of information pieces published), and how to get the
  30 machine name from the LinuxCNC INI file.  The latter is a minor
  31 detail, but I expect it would be useful in a setup with several
  32 machines available.  I am hoping for feedback from the experienced
  33 LinuxCNC developers and users, to make the component even better
  34 before it can go into the mainland LinuxCNC code base.</p>
  35
  36 <p>Since I started on the MQTT component, I came across
  37 <a href="https://yewtu.be/watch?v=Bqa2grG0XtA">another video from Kent
  38 VanderVelden</a> where he combine LinuxCNC with a set of screen glasses
  39 controlled by a Raspberry Pi, and it occured to me that it would
  40 be useful for such use cases if LinuxCNC also provided a REST API for
  41 querying its status.  I hope to start on such component once the MQTT
  42 component is working well.</p>
  43
  44 <p>As usual, if you use Bitcoin and want to show your support of my
  45 activities, please send Bitcoin donations to my address
  46 <b><a href="bitcoin:15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b">15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b</a></b>.</p>