Questions: Mesa 7I92 Leadshine MX4660 4-Axis Step

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22 Apr 2016 16:51 #73720 by sakumar

freeby.mesanet.com/7i92step.zip
is a basic example hal/ini file set for the 7I92

You cal also run pncconf for a 5i25/probrfx2 setup and edit the resulting files
(changing the card name to 7i92 and the hostmot2 config line to include the 7I92s ip address)


I'm taking a stab at generating a .ini file because I want to add the 4th rotary axis to my configuration. Of course, I'll then edit it to use hm2_eth etc.

Here's what my latency histogram looks like. The numbers are a bit high but I'm assuming that's because linuxcnc is in user space. In any case, that's why I'm using the Mesa 7i92.

The Servo time stays at around 105 micro-seconds. So is it OK for me to set the SERVO_PERIOD to 120,000? Is there an advantage to doing this over leaving it at the default 1,000,000?

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22 Apr 2016 17:01 #73721 by andypugh

The Servo time stays at around 105 micro-seconds. So is it OK for me to set the SERVO_PERIOD to 120,000? Is there an advantage to doing this over leaving it at the default 1,000,000?


1000 uS (the default) should be perfectly OK with a latency of 105uS.

You don't need a base thread, by the way.
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22 Apr 2016 17:08 #73722 by PCW
You should leave the servo period at 1 ms (1000000 uSec)
For a step/dir system, There is no real advantage of going faster unless you have multi G accelerations

Also since there will be no base thread, a histogram with --nobase is more reflective of actual latency

Preempt-RT can be nearly as good latency wise as RTAI, it just depends on the hardware, BIOS setup, kernel version, kernel options
phase of the moon etc:

freeby.mesanet.com/h97-g3258-preemt-rt.png
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