cRIO not getting analog input readings

[atokad]

I am using a cRIO-9035 with the following FPGA.vi:

Mod 2: NI 9264

Mod 3: NI 9205

Mod 4: NI 9213

With this code I am able to get a voltage output from the NI-9264, but when I try to send a known voltage to the NI 9205 my readings are oscillating and completely incorrect. 

[smithd]

A very possible answer is: ghosting

However, there are a lot of unanswered questions in your post. For example: Do you have Mod2 physically wired to Mod3, or do you have a signal generator hooked up to mod3? Whats passed on the "Input_FPGA_Cluster"...which is actually the output data? Is is constant? Changing? When you scale it by 15, what is the value? Can it be represented by that fixed point type? How is the input oscillating? By how much? How completely incorrect is it? What are your AI voltage ranges set to? Are they differential or single ended?

My suggestion?
Wire AO0 to AI0 if you haven't and be sure to connect Mod2/com to mod3/com. Com should just be system ground, but it can't hurt to be sure.
Set AI0 to +/-10V range and referenced single ended
Wire aisense to com (shouldn't be important in RSE mode but lets be sure)
Drop down mod2/ao0 and wire up a fixed point control and put a constant of 5.0V in the control
Drop down mod3/ai1 and wire that to an indicator
Press run

If that works (you read 5V+/- a few mV out), that proves the module works right and you can expand. Suggestion 2 would be set AI0 to +5 and AI1 to -5 and see what kind of ghosting appears between channels once you start using the multiplexer.

Edited August 2, 2018 by smithd