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This is sort of un-pncconf related, but..

I can't get the field I/O to work.

I have an 18V power supply connected to VFIELD. I have jumper W1 to the left, so that VFIELD is connected to VIN. The CR2 LED lights up. All of the 7i76 inputs and outputs appear in HAL. If I take a multi meter, between GND and the field power terminals, I get voltage on all the VFIELD pins, and on VIN. If I disconnected field power, CR2 won't light, and HAL won't detect the field I/O.

If I turn off host card power, CR1 won't light and the step/dir stuff stops working. I thought jumper W1 was supposed to supply this logic power from the field power? I don't think something is right here. I suspect it might also be why the field power doesn't work.

If I set an output on the 7i76, HAL shows it as set, but there is no voltage between said pin and ground. If I supply 18V from the same power supply that is connected to VFIELD, to an input pin, HAL shows no change.

The 7I76 requires 2 power supplies,
#1 is 5V from the 5I25, #2 is field power (10 -28V nominal) for the isolated field I/O

Field power is for the _isolated_ field I/O,
There is no common between the computer/step/dir ground and field I/O GND
which is the negative lead of the field power

So if you supply an input signal to the field I/O, this input is relative to the field power - connection
(and must be > than 60% of field power to be recognized as a "high")

Field outputs will also be relative to this signal so if you measure them relative to computer GND and you have a floating power supply they will not be seen

Ah, I see! That would make perfect sense. Is there any disadvantage to using the host card supplied 5V? I just figured I should be using VFIELD to power the logic, as that's how the jumpers were set default.

I have the 18V power supply positive connected to VFIELD on TB1, and the power supply negative connected to GROUND on TB1. The power supply does float, and there is no connection between logic side ground, and field I/O ground anywhere, but it seems like this shouldn't be a problem. All of my field I/O is referenced to the negative on the 18V power supply, not the ground pins on the logic side.

If the watchdog timer isn't satisfied, what gets disabled?

step/dir
All field outputs

Yeah, it's not the watchdog then. The stepgens work just fine.

At my CNC machine now.

My power supply negative is tied to earth ground now. VFIELD and logic ground are tied together. I read 18V between the PC case and the power supply.

The 7i76 will only show up in HAL with jumper W1 in the left hand position, running off host card power, and the field supply powered up. Change any of these parameters, and it will not detect.

As I understand, with the common ground in place between the field and logic sections, jumper W1 is supposed to feed the 18V connected to VFIELD to VIN, which supplies an on-board 5V power supply to power the logic section. Am I mistaken here?

The problem is the field I/O doesn't work, but I feel that being unable to power the 7i76 from field power might be the root of the issue.