Quote:
Originally Posted by compwiztobe
However, since the DIO signal pins are pulled up to the same 5V supply in the roboRIO, I'm sure they will have the same brownout behaviour as the power pins. It doesn't matter if the encoder is powered if you can't read when the signal is shorted to ground.
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The pullup will be a weak pullup (~50k or 10k.). That amounts to 0.1 mA or 0.5 mA of current required to pull the line down under normal use. Say, for the sake of argument, that the pullup was now connected to 0 volts (gnd) due to the brownout. You would only need to source 0.5 mA max to overcome the pullup. This isn't all that much different than sinking 0.5 mA when overcoming it normally, though the direction is different and components are generally rated differently for source vs sink.
This ends up being a rules and robotRIO internals question. Designing a board (and/or using the CTRE regulator) to supply encoder power is far easier than designing an entire co-processor setup, which 971 has been doing for years. I've debugged enough problems on bots over the last couple years which ended up being encoder brownouts that I take this pretty seriously.