[Thad House]

Originally Posted by Andrew Schreiber

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.

The RoboRIO internally does have a Buck/Boost internal to it. It stays powered down to about 4.5v. However, when it dips below 7v, the FPGA disables everything. So it would be a 100% software fix to lower the brownout voltage.

On our practice bot, we actually fed the RoboRIO straight from the regulated 12v. This is because it gets the voltage that is uses from Vin. So if you feed regulated voltage into the RoboRIO it never goes into brownout state. However, this is not FRC legal, and it is required by the rules to be fed straight from Vbatt.

Originally Posted by Jon Stratis

For reference in this thread, does anyone know the brownout voltage for the cRIO? I would ask about the old IFI system, but that had a backup battery for the control system, so it's behavior was completely different.

The cRIO didnt have a specified brownout voltage. The 24v regulator I believe dropped at about 4.5v. But since the cRIO didnt control the power rails on the sidecar, the power from the sidecar would stay on until about 4v, when the sidecar would shut off.

We should start calling the 7v RoboRIO brownout the Virtual Brownout, because it is entirely controlled in software. The hardware brownout doesnt occur until 4.5v, just like the cRIO did.