Quote:
Originally Posted by Joe Johnson
If this were the "real world," I would say, sure, one more constraint, add it to the list. BUT it isn't. This is a system who's job is to control a robot that plays a FIRST FRC game. FIRST was painted into a corner with the cRIO. They had insane time pressures and the had to pretty much take what they could get.
But the RoboRIO? It was designed SPECIFICALLY for FIRST FRC. It was a huge oversight to have anything important loose power, ever.
Another problem is that FIRST's system is SO COMPLEX that it is basically impossible for teams to duplicate what happens out on the field in their pit or even on the practice field.
I am not saying that it would have made that much of a difference but this whole brown out thing cost us in St. Louis. Our first competition match on Carson, something disabled us during auton, then re-enabled us. Shame on us but our code just restarted our auton and ran it again - which broke the robot. Here is the thing. Half of our Qualifying Matches were gone before we got a reasonable answer as to what the problem was and had a work around. It seems to be something related to our robot pulling the voltage below 7V for a small fraction of a second at one point in our auton.
Again, so, yes, shame on us for not realizing that we were close to the edge for 4 prior tournaments where we never saw this problem. But also shame on FIRST for having an unnecessary edge for us to fall off to begin with and for not providing a person with the time and the knowledge to diagnose tricky problems such as ours (had it not been for Mike Copioli and one of his minions from CTRE, we'd still be in the dark about it).
So, that is my team's experience. If you're not on our team, it is easy to say, "Who cares?" Except, I am sure that there were many other teams that ran into problems as well.
Bottom line, I think this is the bad fruit that grew from a bad seed. FIRST should have made this a non-issue with the new controller.
Dr. Joe J.
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Honestly, the issue can probably be solved fairly easily with a buck/boost converter to the roboRio. A quick search on Amazon showed a handful that should work (Max power consumption of the roboRio is 45W according to NI Specs) and they cost under $30. The RoboRio actually has quite a wide input voltage range but feeding it from VBAT just seems like a bad idea. And I'd bet someone smarter than me with electronics could do it even cheaper than what I can find in 10 minutes on Amazon.
Proposed solutions aside - this was a well documented failure mode* of the RoboRIO and I find it extremely concerning that the neither FTAs nor CSAs at CMP were able to identify the cause.
*I remembered having conversations with Brando about the point this happened and what we'd have to change in how we designed robots well prior to build when spec sheets first started coming out.