r...@sdf.org (RVP) writes:
>On Wed, 16 Oct 2024, Ramiro Aceves wrote:
>> netbsd-raspa4$ { sleep 1; stty -f /dev/ttyU0 9600 raw clocal cread
>> -crtscts; } & cat -u -v /dev/ttyU0
>> stty: /dev/ttyU0: Resource temporarily unavailable
>>
>Wrong device--use /dev/dtyU0.
You don't need to open the device twice and you don't need non-blocking mode.
( stty 9600 raw clocal cread -crtscts ; cat ) < /dev/dtyU0
will configure the interface and read from it. The dial-out device will
avoid waiting for a carrier-detect signal, so the open is not blocked.
Then stty disables flow control, so that cat then won't stall on the
3-wire connection (clocal and cread aren't necessary then, or you could
just use clocal).
The next problem is then the binary protocol. The shell won't be
able to parse it and 'cat' will try to read big chunks. You can
try to work around this with dd, e.g. this would read single byte
chunks.
( stty 9600 raw clocal cread -crtscts ; dd msgfmt=quiet ibs=1 obs=1 | hexdump
-vC ) < /dev/dtyU0
