Using the on-board serial port for modem

Hi

I'm having problems using the on-board serial port for an RS232 GPRS modem
I have.  I have set the console to /dev/ttySAC1 in the bootloader, but
still I am unable to chat with the modem using /dev/ttySAC0.

I'm using picocom to test the modem.  If I attach it to the USB port with a
PL2303 adapter, it's working just fine from /dev/ttyUSB0, but I need to
free the serial port for another device.  Using the on-board RS232 port
would be perfect.

Anyone know if I missed something obvious?

Also, is ttySAC0 a fully qualified serial port with all the modem lines
attached (for example with the DTR line)?

Hi Stian,

   There are two more things that can prevent you from talking correctly to
ttySAC0.

   One of them is the linux console (not kernel console) that "lives" on
that port. You can disable it by editting /etc/inittab and making sure that
you comment any line there that points to /dev/ttySAC0, but before
disabling this console you should make sure that you can access the board
by some other mean such as SSH or Telnet.

    The other one are the kernel low-level messages that appear too on
ttySAC0 if you do not disable this messages you will get garbage on your
serial communication. To disable this messages you should edit
/etc/sysctl.conf and uncomment the line that reads :

kernel.printk = 4 4 1 7

    Now you should be able to use ttySAC0 as you like.

Regards,
  Isaac

Hi, 
I have the same problem, I have the EM2440-III but I do'nt have any ttySAC0
on the /dev/ whereas when i input [# dmesg | grep tty

I have :

Kernel command line: noinitrd root=/dev/mtdblock2 init=/linuxrc
console=ttySAC0
console [ttySAC0] enabled

in my etc/
cat inittab
# /etc/inittab
::sysinit:/etc/init.d/rcS

::once:/usr/sbin/telnetd -l /bin/login
::ctrlaltdel:/sbin/reboot
::shutdown:/bin/umount -a -r

but i don't have any /etc/sysctl

I don't understand i work on this all the day, I don't success to resolve
my problem by myself