Mesa 7i92 with 7i77 . No PWM after flashing bit file

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09 Dec 2021 19:54 - 09 Dec 2021 19:55 #228724 by DeRooij TSC
Hi all.
I am completely new in LinuxCNC but after searching this forum I already learned quite a bit I think.
I have a Padovani teach in lathe which I am trying to convert to Linux. The servo's and spindle are regulated via +-10V, so I got a 7i92 ethernet motherboard with a 7i77 servo/analog daughter board. I flashed the 7i92 with the 7i92_7i77x2D bitfile but I get no PWM generators when I do the readmhid command. When I look at the 7i92_7i77x2D.pin file, I don't see any PWM as well.
When I look in another pin file (I believe it's 7i92_7i85x2D, but not sure, I am at home right now) I do see 2 PWM generators. When I flash the 7i92 with the 7i85 bit file I do have those 2 PWM generators when I do the readhmid. But of course, that won;t work.

It seems that the 7i92_7i77x2D bit file is not complete?

Anybody has any idea?
Last edit: 09 Dec 2021 19:55 by DeRooij TSC.

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09 Dec 2021 20:01 #228726 by PCW
The 7I77 analog is interfaced via a sserial connection
so there are no PWM generators in the firmware

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09 Dec 2021 20:23 #228728 by DeRooij TSC
Ah, okay. I thought you should always have PWM;s in the readhmid if you use them.

Then my problem shifts to my hall I guess?

Problem is that I don't get action from the PWM when the drives are enabled via Linux.
Enable signal is working, servo's are working if I put 1,5V (battery) on the +-10V wires, encoders work and count correct according to the DRO.
When the drives are enabled via the 7i77, the servo's start drifting.
When the drives are enabled without the 7i77, the servo's don't drift or at least very little. (drift is adjustable in the drives)

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09 Dec 2021 21:01 - 09 Dec 2021 21:01 #228731 by PCW
How is the PID setup (P term mainly) and how is the 7I77 analog output wired to the drive?

(I ask about wiring because I have seen people try to reverse the analog out polarity
by swapping ground and analog in at the drive, thereby shorting out the 7I77 analog outputs)

Does the voltage out of the 7I77 reflect the analog out hal pin (relative to the analog out scaling)?
Last edit: 09 Dec 2021 21:01 by PCW.

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09 Dec 2021 21:27 #228737 by DeRooij TSC
P has been tried with several values. Like 5 to 50 and some in between.
Analog outputs are wired according to the 7i77 manual. pin 3 (and 7) gnd, pin 4 (and 8) analog out.
I have not seen any voltage on pin 4 and 8 except the tiny constant value that likely let the servo;s drift.
Analog out scaling is set at 10 in the hall I believe. Maybe that is the problem? Encoder scale is 1000, max speed is 41.67mm/sec. I,m not able to post the hall at this moment, sorry for that.

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09 Dec 2021 22:00 #228741 by PCW
I think this will need posting the hal/ini files
or watching the analog output values in hal
and seeing if the physical analog outs values match
(they should if the scale is 10)

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09 Dec 2021 22:10 #228743 by DeRooij TSC
I will try to post those tomorrow. Bed time for now over here...

Thanks so far!

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10 Dec 2021 22:53 #228829 by DeRooij TSC
So I copied the hall and ini file, but I'm on  windows PC right now. I hope this works?
Attachments:

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10 Dec 2021 23:21 #228832 by PCW
Looks basically ok except that you have "num_pwmgens= 3"
which should cause an error since a 7I77 configuration would not normally
have any pwmgens.

I would disconnect the 7I77 analog out from the drives and monitor
x-output (with halmeter or halshow) as you jog back and forth
and verify if the 7I77 analog output matches x-output
(with a P of 5 you would expect a analog output voltage of 5V per MM
of following error)

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11 Dec 2021 08:15 #228860 by Clive S

So I copied the hall and ini file, but I'm on  windows PC right now. I hope this works?

Not related to your problem. But I see a small problem with the ini file. Generally the axis and joint should be the same.

[AXIS_X]
MIN_LIMIT = -0.01
MAX_LIMIT = 200.0

[JOINT_0]
MIN_LIMIT = -200
MAX_LIMIT = 200.0

[AXIS_Z]
MIN_LIMIT = -100.0
MAX_LIMIT = 0.01

[JOINT_1]
MIN_LIMIT = -100.0
MAX_LIMIT = 200

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