Issue with Talons

[agartner01]

Originally Posted by JewishDan18

Hi all, I was hoping to get some help with a strange problem with some Talons.

Tonight we decided to do driver tryouts with a simple robot consisting of a drive train with two CIMs to each side, all controlled over Talons. Normally it drives fine, but occasionally while driving straight the side going forward (the lights on the Talons are green) reverses for a very quick moment, going backwards. The lights on the Talons turn red when this happens. We are using simple Arcade Drive code, and I've checked the values being sent to the Talons in the code, and they are not reversing at all there. This happens when driving straight forward and backwards at full power (so all 4 Talons have had the issue), but not when purely turning.

We think there is an issue somewhere between (and not including) the crio and the Talons themselves, since it happens to all 4. Additionally, once when powering the robot on one side of the robot moved at a high speed for a very short amount of time, which leads us to rule out code issues.

Tomorrow we plan on replacing the Digital Module, the Digital Side Car, and the cable connecting the two one at a time to see if any of them are causing the issue. Is there anything else we should be doing or checking for that anyone can think of? I tried to give all relevant info but if anything else is needed I can provide it. Thanks!

I'd like to add that my team has experienced the same problems... No idea how to fix them.

[KrazyCarl92]

Here's what we have already tried and some additional info:
We tried turning the robot off and back on. Sometimes this fixed it, other times it didn't, and the problem would intermittently come back after varying amounts of time.
All 3 lights on the digital side car are on.
The observed effect is that the robot is commanded to move forward (and only forward) and it starts out doing so, then pulses a turn to the left, then continues on its way forward.
This happens only when the talon is commanded to go in the green direction. It does not occur in the red direction (or we have yet to observe it).
All 4 of the talons are in coast mode.

[Alan Anderson]

A brief twitch in reverse can be a sign that the robot is getting disabled for a moment. If the PWM signal is interrupted for just the right amount of time, it is possible for the speed controller to misinterpret the interruption as a valid command. Look at the Diagnostics tab of the Driver Station and see if there are any helpful error messages.

[RufflesRidge]

Have you tried calibrating the Talons?

[KrazyCarl92]

Originally Posted by RufflesRidge

Have you tried calibrating the Talons?

Yeah, we have calibrated them.