Mesa 7i96 options for PWM output?

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04 Apr 2018 20:52 #108405 by jason.jenkins
Hello. I'm new to linuxcnc but have been able to get my DIY router up and running using the Mesa 7i96 card via ethernet with only a few hiccups along the way. I'm planning to add a laser to my router in the future which would use a 0-5v PWM signal for power control. What options do I have to make this work?

As I understand it, the 7i96 doesn't have a hardware PWM output, correct? Can one of the SSR outputs be used for a software-generated PWM signal? How about one of the pins on the DB25 expansion connector? Or do I need to add a daughter card to the board? If so, which one?

Thanks!

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04 Apr 2018 21:32 #108407 by PCW
if you dont need all 5 step/dir outputs, its probably simplest to steal one and use it for PWM
This would require different firmware but its a common requirement so it probably should be
made as a standard option
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04 Apr 2018 23:01 #108410 by jason.jenkins
I was afraid that might be the most straightforward way. Unfortunately, I'm using all 5 stepgens (dual X & Y steppers + single Z). Any other, next-best options, short of buying a 7i76e, which was my original plan, but they were out of stock at the time, and I'm impatient. :-)

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04 Apr 2018 23:38 - 05 Apr 2018 00:20 #108412 by PCW
If you download the latest 7i96.zip file from Mesa you could use:

7i96_5abob_d.bit

This is a configuration for that ubiquitous 5 Axis Ebay BOB on the 7I96s expansion connector.
It has a PWM output on pin 1. If you use this output, you must be careful not to short it to
power sources > +7V or < -0.5V. If you add a ~300 Ohm series resistor it will be a lot safer.

Other options are custom configs using the RS-485 XMIT data as a PWM output or another custom config using
the 5 Axis Ebay BOB as a buffer (so the PWM output would be wired to one of the BOBs step/dir outputs)
Last edit: 05 Apr 2018 00:20 by PCW.
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04 Apr 2018 23:56 #108413 by jason.jenkins
I'll give it a shot. Thanks!

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