Hi everyone, I'll try to keep this short.
We're using a thermocouple on our hotend so we can hit higher temperatures and are using a max31855 to read it. I confirned that the thermocouple and the board work by hooking it up to an arduino.
Essentially, I can get get initial temperature readings via pronterface that make sense. But as soon as power is run through the stepper motors (I move them briefly), the percieved temperature drops immediately (like to -60C at times). When I turn off the power to the motors (doing it through pronterface), the temperature jumps right back up.
The SPI wire lengths are short, I cut them to about an inch and I'm using shielded thermocouple wire. I grounded the shield to the chasis, not the smoothieboard ground (could that be an issue?).
At the recomendation of a few people on irc, I measured the voltage across the 3.3v and gnd pin I'm using while running the steppers; I saw no drop.
Right now, my only idea is to try wrapping wire in copper tape.
Could this be an emi problem from the stepper motor wire leads? Or could this be an issue with firmware? I can provide more information if needed. Has anyone seen this issue before? Any ideas? This is pretty urgent as I'm on a deadline, so any help would be greatly appretiated.