Basic configuration of LinuxCNC 2.8.2 + MESA 7i76e + iHSV57 servo

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30 Jul 2022 15:22 - 30 Jul 2022 15:23 #248674 by knipknap
Hi,

I am trying to set up a Raspberry Pi 4 + LinuxCNC 2.8.2 + MESA 7i76E + 4 iHSV57 servos.

What works: I got LinuxCNC installed (though only using the inofficial image linked here: forum.linuxcnc.org/9-installing-linuxcnc...cnc?start=130#238020), and can ping the MESA card. After starting LinuxCNC, I select the configuration (I used the basic configuration from Talla: www.talla83.de/linuxcnc/iHSV57_2_8.zip) and it starts fine.

However, there are two problems:
- After a few seconds I get the error message "Unexpected realtime delay n task 0 with period 1000000"
- When trying to jog any axis, the servo doesn't move.

I tried to resolve the error message first. The latency-test reports a maximum latency of ~253000ns. I tried to put this into the stepconf tool, but the maximum allowed value there is 50000, so I am not sure how to proceed. I also found this page: linuxcnc.org/docs/html/motion/tweaking-s...l#cha:Stepper-Tuning but am not sure where to get the required attributes from, also for the .ods document that is linked in there. I am also unsure if that document is even relevant for me, as it refers to "software stepping" - is this what is done when using a MESA card? Or would the MESA firmware generate the pulses?

Any hints on how to proceed?
Last edit: 30 Jul 2022 15:23 by knipknap.

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30 Jul 2022 15:36 #248678 by PCW
How did you create you hal.ini files?

On a RPI, you may have to raise the servo thread period to 2000000 ns

If you cannot get step/dir drives to move (and the wiring is correct)
the most common issue is too short step pulses (start with 5000 ns)

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30 Jul 2022 15:59 #248680 by knipknap
I was using the .ini file that was included in the linked .zip from Talla, without any changes.

I now changed SERVO_PERIOD under [EMCMOT] in iHSV57.ini to 2000000, and the error message no longer appears.

I also tried to change STEPLEN and STEPSPACE under [JOINT_0] to 5000, but then the following error appears: "hm2/hm2_7i76e.0: stepgen.00.maxvel is too big for current step timings & position-scale, clipping to max possible"

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30 Jul 2022 16:23 #248681 by knipknap
Ah-ha! After also changing STEP_SCALE to 320, it is working great! :-) Amazing!

Thanks for the help!

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