2015 RoboRIO/Control System Feedback

[Kevin Sevcik]

Spawning a separate thread for Positive/Negative control system feedback, so it doesn't get lost in the mass of replies to 2015 Lessons Learned. I figure it'll be easier for our NI denizens to keep track of things in here.

Our experience was overall positive. We were already using CAN, and the new 2-wire native CAN bus and web config made things so much simpler that setting up our 9 Talon SRXs was laughably easy. I nearly giggled updating the firmware of all the devices via the web config.

My only bad experience was with the analog inputs. We had string pots for feedback on our elevators, and we ran into a baffling issue trying to add any other sensors to the robot. We wanted an IR prox switch, IR distance sensor, or ultrasonic to tell when we had a tote to stack, but adding any one of those screwed with the string pots. I'd plug in the IR distance sensor and the elevator would start twitching as the signal for each pot started bouncing around. I originally figured it was because our 5k pots were outside the 3k impedance NI recommends, but switching to 1k pots at Champs didn't help. I finally gave up worrying about that and plugged in our navX MXP board just to see how bad that would make things. Except plugging in the navX magically made everything stable, even when I plugged in the previously problematic IR distance sensor. I'm still slightly lost as to what was going on, but I'm hooking up an o-scope to the bot when the crate shows up to see if I can at least isolate the problem to the 5V, GND, or signal lines.