Which board did I kill?

I had a working setup with a 5i25 ->7i85s -> 7i84.
I had steppers on the 7i85s (temporary while I sort out servos), and all inputs on the 7i84.

I was experimenting with some servos and messed up the wiring. I tied the pin 20 and 22 (negative halves of two differential pairs) together on the 7i85s:
19 TX2 FROM 7I85S
20 /TX2 FROM 7I85S tied to gnd on servo end
21 TX3 FROM 7I85S
22 /TX3 FROM 7I85S tied to gnd on servo end

After this, step outputs no longer function on any of the differential step outputs. All other functions work. Estop and limit switches work (7i84 handles these, uses CAT6 serial to 7i85s), direction pins on 7i85s go low and high as expected, and axis throws no errors.
Scoping the step pins on all axis shows zero activity.

I tried various backups of my linuxcnc configurations (all known working) with no change.


I have ordered a 7i76 (more suitable for my application) as a replacement for the 7i85, but I just realised that as I only tied one channel's differential pairs to GND, surely I'd only have damaged one RS422 chip on the 7i85s. IF that's the case, then all other channels should work. Does this mean that I've damaged the stepgen on the 5i25?

You probably damaged one of the quad differential drivers on the 7I85S
( each driver chip drives 4 output pairs )

That's what I initially thought, but wouldn't only two axis fail then? (for four oupput pairs). I can't get step pulses on X, Y, Z, or A.


Also, related note, I ordered a 5i25/7i85 plug and go kit, and I'm now getting a 7i76. Will I need different firmware for the 5i25?

Not sure how the chips are wired so its possible

The 7I76 needs 5i25_7i76x2.bit firmware