Sticky Fault?

So, our robot uses pneumatics to actuate the ball into our shooter. This all works fine and dandy during normal matches where we run our reach auton, but whenever we try to run our high goal auton, our PCM finds a sticky fault, disabling our ball pusher, rendering our shooter useless for the rest of the match. Video of this occurring. This is repeatable, as we were able to repeat it consistently in the pit by using Practice match mode on the Driver Station, then clearing the fault each time through the Web Dashboard and then power cycling the robot. This always occurs (as in the PCM diagnostic light turns red) when the ball pushing single-acting solenoids are set to (false) in the autonomous code.

We use C++, if that matters, and our PCM version is 1.65. How hard would it be to determine whether this be a code issue or a wiring/pneumatics issue? We would really like to figure this out as we have one more event left and would like to score in the high goal during autonomous. I’m sorry in advance, as we are currently on spring break so I do not have access to the code to post if necessary, but I could try to get it as soon as possible.

Thank you so much!

Do you know what specifically is causing the fault? (ie. the compressor) You can do this by just clicking the self test button once and will tell you were the error is. I would suggest starting there.

Team 74 had a similar issue last weekend at Walker Warren. We found out that the reason the sticky fault occurred is that we unplugged the compressor from the PCM. We haven’t had any recurring issues with it, but our PCM continues to blink yellow. If you have an extra PCM, I’d recommend switching it out if possible.

Since it only happens in a given Autonomous mode, I would assume this is a code issue. In a regular match (during Teleoperated), do you change the state of the PCM in any way similar to your High Goal auton?

It sounds to me like 1 of 3 things:

a) Your compressor is faulty and/or not connected.
b) Your CAN bus is not connected properly to the PCM
c) Your CAN bus is being over utilized. Check the Driver Station Logs for CAN % utilization.

A and B both come from the CTRE PCM Users Manual

We do run an off-board compressor, is that possibly why? If so, how would we program it so an off-board compressor does not cause these issues?

My apologies, in the case of an offboard compressor that should not cause an issue. The issue I’m more talking about is if the compressor port on the PCM is being shorted out

What is the sticky fault? If it is compressor related, moving the pressure switch to off board will stop the compressor from trying to run during autonomous. That can also be done through software. Are you powering valves differently? Simultaneous operation of multiple valves might be overdrawing the PCM. Solenoids have an inrush current that can be high and a holding current which is generally fairly low. Solenoids also have a voltage spike when denergized. Simultaneous energizing of one solenoid & denergizing of another might be a problem?