We have a machine here with oodles of 8 port serial module cards in
They are usualy initialised by the normal
setserial /dev/ttySxxx uart 16550A port 0xXXX irq Y
however, seems that lately we can send data (eg: init strings) to teh
modems and the modems can recognise DTR drops and TR signals but no
data will come back from the modem.
Is there anything that anyone has seen or known of that may indicate
what this problem is?
You didn't say what version of the kernel you're using. (Grumble; we
need a FAQ about intelligently reporting bugs, and make sure everyone
However, if you're using Linux 2.1.8 or later, the problem is that your
application is probably not setting the CREAD termios flag. Starting
with 2.1.8, I added support for this required POSIX.1 flag; if CREAD is
not set, the serial port receiver is disabled and the tty won't get
any input from the modems.