I’m unable to connect to the debug UART (to diagnose a boot problem). I have tried two different FTDI adapters, three Prolifics, and one CP210x. I’ve tried them all on a Windows desktop and a couple of them on a MacBook. Every time that I connect, I get this type of garbage:
I’m starting with 115200/8N1 and no flow control, but I’ve also experimented with other speeds, bit counts, etc. If I setup the USB UART with a loopback, everything looks good. I’ve tried putty, Tera Term, and zterm with the same effect.