> On Aug 31, 2023, at 1:16 AM, Brett Lymn <bl...@internode.on.net> wrote: > > On Wed, Aug 30, 2023 at 09:34:31PM -0600, Brook Milligan wrote: >> I am trying to communicate with uart4 on a Beaglebone Black, but cannot open >> /dev/tty01; open(2) just hangs. I would greatly appreciate tips on how to >> track down the issue. >> > > Perhaps it is hardware handshaking that is missing? Is DTR asserted? If you > cannot do > the hardware signalling you may need to set the line discipline on the tty to > disable > hardware controls.
Yes, of course; there are no modem control lines. Thanks for the reminder; I knew this onetime, but I guess those neurons flew away. Setting up the line discipline makes a big difference (of course). Now the device opens and I can set termios parameters. However, a write fails and hangs the board hard: no keyboard response, no response to pings. I have attached the test program below, and would appreciate more eyes on it from (the many) people who obviously know serial line programming better than I do. It gets as far as the write() call, but no further. If the program looks reasonable (the specs for the remote end are 7 data bits, even parity, 1 stop bit, no flow control, 9600 baud, although the hang occurs with or without anything on the other end), I would like advice on where to turn next to get information on where (and why) it is hanging. Thanks a lot for your help. Cheers, Brook
serial.c
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