Robot Twitch

[PAR_WIG1350]

Originally Posted by Chris Hibner

We had a similar issue where the robot twitched every now and then (sitting still - type A) and there seemed to be a time delay from all of the operator inputs to when the robot would start moving.

We put ElapsedTimes.vi into the PeriodTasks loops and in Teleop. We found out that our fast loop and teleop were taking about 250 ms to complete!

At first, we couldn't figure out what the problem was. Our code was bigger than previous years, but we didn't think by THAT much. We don't use sub-loops. We had no idea what could be blocking the code and taking up so much time.

Then we figured it out - we had an analog input that was configured for an incorrect channel. That caused an error, which for some reason bogs down the entire system. We allocated it to the right channel and voila, our loop times bacame exactly what they should be. I've since confirmed this behavior with a missing solenoid card. It seems that any misallocation causes the system to slow to a near crawl.

So, there are 2 things to take from this:

1) Coming out of Begin.vi, check your error output (assuming you have all of the errors from the Open blocks going into a "MergeErrors" vi). Make sure you have no errors. If so, fix them - it just might solve your problem.

2) Greg: can NI do anything about this? It seems like bad failure mode that if a piece of hardware becomes dislodged or someone fat-fingers a channel number, it causes all of the code to become blocked for 200+ ms. Please don't take this as me being a big complainer - I think NI has done a fantastic job and much kudos to all of you for always being helpful.

(BTW: when it happened to us, we had two analog devices allocated to the same channel (copy and paste - forgot to change the channel #). I noticed it again when we were doing some code development on a second cRIO: our code uses solenoids but the second cRIO did not have a solenoid card installed.)

Assuming we don't use solenoids in the code, would not having the 24volt DIO module (the solenoid module) in the cRIO cause this issue?