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+--- Thread: UART switch not working [EDIT: I got it working] (/showthread.php?tid=15178)
UART switch not working [EDIT: I got it working] - kileel - 10-24-2021
So I'm attempting to boot OpenBSD on my PBP, which requires serial console access. So I have a serial adapter, and I've flipped the UART switch on the main board. According to the wiki, the sound should be disabled and I should be getting output on the serial port. However, the sound is not disabled and I get no output on the serial port. I checked the electrical function of the switch and it seems to be switching appropriately. Is this just a firmware problem? Has anyone else encountered this?
EDIT: I forgot Rx and Tx have to be switched on the host device to communicate with the target device. I have it working now! Thanks to @KC9UDX for the help.
RE: UART switch not working - KC9UDX - 10-24-2021
So you are still getting sound?
Are you sure you have a good interface cable and are using the correct settings on the terminal end?
RE: UART switch not working - kileel - 10-24-2021
(10-24-2021, 06:45 PM)KC9UDX Wrote: So you are still getting sound?
Are you sure you have a good interface cable and are using the correct settings on the terminal end?
I think so, I'm using the baud settings reported in the wiki. Are there other settings that are necessary that aren't reported there? I don't think my interface could be the problem...
I was under the impression that while the switch is turned on, no sound comes out of the device regardless of whether an interface is connected, is that wrong?
RE: UART switch not working - KC9UDX - 10-24-2021
You should still have sound from the main speakers, just not from the headphone jack. Where did you get the cable? There are cables that are wrong and Pine64 even used to sell them. The correct one is 3.3V, the wrong one is 5V. It might be possible a wrong cable has RX and TX swapped, too.
Make sure your terminal is set for 1.500.000 baud. I know the first time I did it, I misread it as 150.000 baud.
RE: UART switch not working - kileel - 10-24-2021
(10-24-2021, 10:40 PM)KC9UDX Wrote: You should still have sound from the main speakers, just not from the headphone jack. Where did you get the cable? There are cables that are wrong and Pine64 even used to sell them. The correct one is 3.3V, the wrong one is 5V. It might be possible a wrong cable has RX and TX swapped, too.
Make sure your terminal is set for 1.500.000 baud. I know the first time I did it, I misread it as 150.000 baud.
I made a cable from old headphones and a Tigard tool switched to 3.3V, and I double checked the values with a meter. I think I had 1.5M baud set correctly, but I'll try again tomorrow.
Thanks for the clarification about the sound behavior, that wasn't obvious from what I had read!
RE: UART switch not working - KC9UDX - 10-24-2021
If it still doesn't work, try swapping TX and RX. I don't have a good reason to doubt the wiki on that but it can't hurt to try it.