Manually using GSM

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When men were real men and typed their own AT commands...

Thankfully, this may now be partially obsolete. The dialer now works!

This is a short guide how to manually get GSM going.



  • GTA01Bv2 or GTA01Bv3 with very recent u-boot bootloader, providing usbtty (serial over USB) support)
  • Do not connect any debug board!


Booting the system

  • Make sure the rootfs you use has 'auto usb0' in /etc/network/interfaces
  • Configure the host's usb0 interface to netmask See USB_Networking
  • ssh to root@

Disabling the getty

Our default images all have a getty running on /dev/ttySAC0, please edit /etc/inittab and disable the getty on that port

Reducing the loglevel

NOTE: You don't need this in kernel builds with patchset ≥ 1288

To keep the kernel from writing to /dev/ttySAC0, you need to use dmesg -n1.

Powering up the GSM Modem

  • verify there is no getty or any other app running on /dev/ttySAC0
root@fic-gta01:~$ lsof | grep ttySAC0
  • If gsmd is using the GSM modem, shut it down with
root@fic-gta01:~$ /etc/init.d/gsmd stop 
  • power-up the GSM Modem
root@fic-gta01:~$ echo "1" > /sys/bus/platform/devices/neo1973-pm-gsm.0/power_on

Connecting to GSM Modem (using socat)

  • If you have the command socat (built and installed):
root@fic-gta01:~$ socat - file:/dev/ttySAC0,crtscts,crnl
AT-Command Interpreter ready
  • If you don't have it, do:

opkg install

Connecting to GSM Modem (using cu)

If you don't have socat, you can use cu, although it has problems with file permissions and hardware flow control.

  • change permissions on ttySAC0
root@fic-gta01:~$ chown uucp.uucp /dev/ttySAC0
  • setup /usr/spool/uucp
root@fic-gta01:~$ mkdir -p /usr/spool/uucp
root@fic-gta01:~$ chown uucp.uucp /usr/spool/uucp
  • enable CTS/RTS flow control
root@fic-gta01:~$ stty -F /dev/ttySAC0 crtscts
  • access the GSM Modem UART
root@fic-gta01:~$ cu -l /dev/ttySAC0
AT-Command Interpreter Ready

If it hangs on "Connected" message then probably your device has a non-working GSM modem - check Bug #256, also you may want to try powering off the modem then on again as this worked for me

cu seems to have problems with the hardware flow control. The one way I always managed to get GSM working is to start cu first and then on a different console issue the stty command. --DanielWillmann 01:15, 20 March 2007 (CET)

  • close the connection with <Return>~~.<Return>


Using it manually

Registering with the Network


List available carriers

This can take a few seconds to process but will list the available carriers


Answering an incoming call


Dialling an outgoing call

To actually be able to talk you have to configure your audio accordingly

root@fic-gta01:~$ cd /etc/alsa/
root@fic-gta01:/etc/alsa$ wget
root@fic-gta01:/etc/alsa$ alsactl -f /etc/alsa/gsmheadset.working.state restore

Up the "Amp right" volume to hear the speaker on both ears, then dial (note the ; at the end of the dial string, this signifies a voice call, if you omit the ; it is regarded as a data call).


If you get NO CARRIER, try...


ie, ATD+<country_code><area_code><phone_number>

Hanging up


Using gsmd

You can use the gsmd and libgsmd-tool programs to have a slightly more high-level interface to the GSM Modem. It's still console based, though.

For further instructions, see gsmd

Using tui

Tui (available from sourceforge) is able to do all this. It is still text-based, but input-rxvt can take data from touchscreen, so you can actually do the calls using your finger. It also plays wav file on incoming call, so it is theoretically usable. It even does caller id.

Manually using GPRS

See Manually using GPRS

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