I'm running into a different problem with this replacement Betz board that I can't figure out.

It mostly works, including its I2S digital inputs.

But sometimes the RX/TX serial communication with the arduino does not work.

When I power it straight from the UART with nothing else connected but the USB cable, it works. I can upgrade its firmware and type commands in putty and whatnot, and everything looks right.

But when I power it with 5v from the 5v pin, I get garbage on the serial port, everything it sends to the Arduino is mixed with random garbage characters. It can work for brief periods but then stops working again.

No chips are getting hot or anything.

If I plug in both the Arduino into one USB port and the Betz board into another USB port (with JP4 disconnected) then everything looks correct on the serial port. It's almost like it needs two 5v supplies to keep it going or something.

Except... that last thing also eventually stopped working.

Wondering what I've done wrong here. :-)
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Tony Fabris