Need help, Mesa 5125 & 7i76 combo and can't get it to move stepper -resolved

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26 Sep 2020 11:36 - 07 Oct 2020 09:24 #183836 by centreline
Hi all,
My problem is I can't get my machine to move any axis at all.

On my machine (a bridgeport interact), Ive converted from two parports and a older install of linuxcnc to a Mesa 5i75 and 7i76 daughter card and version LINUXCNC - 2.7.14.
As a parport controlled machine it worked but I felt I was hitting speed issues & replaced the pc after it crashed mid cut a few times for a faster one after that turned out to have more jitter.
Electrically, the psu and stepper drivers hardware are unchanged, I've rewired the stepper control pins for the 7i76. The steppers are DM860A's (www.longs-motor.com/stepper-motor-driver-dm860a.html) and I have 70v dc from a transformer psu and have verified the voltage from it.

Ive hooked the steppers up according to a diagram Norbert posted in this thread, extract posted below to make it easier to see for this case. forum.linuxcnc.org/27-driver-boards/3191...ection-sheet?start=0 . My previous stepper wiring had 5v connected to ena+ dir+ and step+ permanently but I wanted ena to be under the control of the card rather than hardwired as previous as 7i76 has facility for this. When I power up the 70v dc rail for my steppers, they lock (as they should), so I think that indicates that the power side is wired and ok.


attached a tar of my config directory, currently I can see the limit switches wiring on the 7i76 pins and in the gui (and it stops when estop or a limit switch is it, home responds to home etc). The mpg I have wired in to the first encoder as I currently have no spindle encoder, and when its moved I see signals jitter on pins (but the axis doesn't move, last digit of axis position display jitters when mpg rotated & something sets the position back to the original value when its jogged via mpg and no movement of the stepper happens, mentioning this in case its related). I haven't done spindle setup yet.
I've tried massive values in DIRSETUP, DIRHOLD, STEPLEN and STEPSPACE in the ini file after some suggestions on irc, but apart from triggering a warning when starting Axis gui that I'd exceeded max values and they had been set to maximum values possible, no change. The files were originally created with pncconf but I'm quite happy to hand edit things to tweak.

File Attachment:

File Name: bp_lcncconfs.tar
File Size:40 KB


My 7i76 setup is I have a external 24v psu feeding the field power, and use 5v pass through from the 5i25. Both the power leds are lit on the 7i76. I've verified that 5v is at the en+ referenced to the gnd when the axis is enabled.

Any ideas? I've been going round in circles trying to work this out for myself already, I can move/jog/home a machine axis in the gui, but although the values change, it never actually physically moves.
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Last edit: 07 Oct 2020 09:24 by centreline. Reason: marked it resolved

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26 Sep 2020 11:45 #183839 by centreline
I'll attach the ini and hal directly also as a attachment to make it easier to view.
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26 Sep 2020 11:51 #183840 by centreline
Finally (sorry to add to confusion), I mentioned estop and mpg, they are missing from the above hal file because I stripped everything out looking for the issue, but in case its relevant here was the version with my mpg/e-stop or2 etc configured.

File Attachment:

File Name: test_mesac...9-26.hal
File Size:13 KB
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26 Sep 2020 14:28 #183848 by PCW
1. The maximum velocities are _really_ tiny (X is 0.29 mm/second max)
is it possibly moving and not noticed?

2. Are you certain about how enable works?

3. Did you try single ended drive?
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26 Sep 2020 15:31 #183851 by centreline
1) I think so, but I'll try higher values. In the past I could feel/hear it when it microsteps a tiny amount.

2) Last time working I had enable pin, step & dir +ve hard wired to +5v and it was enabled permanently (wrongly I know, it used to make a clunk noise from the steppers on boot before the card was initialized, this is one of the things I wanted to improve).
In Longs DM860A driver literature is this :-
"Enable signal: ENBL+ is the positive end of direction input pin. This signal is used for enabling/disabling the driver. High level for enabling the driver and low level for disabling the driver."
So I think that means +5v at the ENBL+ referenced to ENBL- means drive is enabled.

3) With parallel ports config, I had the following line setting them to step_type=0 :-

loadrt stepgen step_type=0,0,0,0,0 ctrl_type=p,p,p,p,v
longs documentation says this :-
PUL +,PUL- Pulse signal, PUL+ is the positive end of pulses input pinPUL- is the negative end of pulse input pin
DIR+,DIR- DIR signal: DIR+ is the positive end of direction input pinDIR- is the negative end of direction input pin

but then they show two diagrams, this one which I followed with parport setup because I switched the -ve with the pin :-


And below this one.


Right now, I have neither of these pins wired together, I've just followed the schema posted above, direct wire terminal on dm860a to wire terminal on 7i76. Should I try common'ing these pins together again?
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26 Sep 2020 15:37 #183852 by centreline
Let me answer 3) more clearly, no, but I think it shouldnt be in single ended drive mode because previously I had it working fully in step/direction.
I'll post my previously working with parallel port bob's HAL here in case it helps clear any confusion up.

File Attachment:

File Name: bridgeport...robe.hal
File Size:6 KB
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26 Sep 2020 16:39 - 26 Sep 2020 16:40 #183855 by PCW
Single ended mode refers to wiring:

single ended mode:
DRIVE +PUL  7I76 +5.
DRIVE -PUL  7I76 -STEP
DRIVE +DIR  7I76 +5
DRIVE -DIR  7I76 -DIR

Also note that in almost every step motor drive I have seen, applying 5V to "ENA"
disables the drive
Last edit: 26 Sep 2020 16:40 by PCW.
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26 Sep 2020 17:09 - 26 Sep 2020 17:10 #183859 by centreline
Well posting my hal did clear up some confusion, mine!

I've pulled the 5v connection from the ena pin on the driver and wired the 5v to +PUL and +DIR to make it single ended, and now I hear it microstepping (really slowly, as you previously suggested it would be). Thanks.
I can hammer/tune things in my config out now it actually does things.
Last edit: 26 Sep 2020 17:10 by centreline.

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