1. Use the built in logs to identify the different serial ports on your system.

root@monitor:~# dmesg | grep ttyserial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A serial8250: ttyS1 at I/O 0x2f8 (irq = 3) is a 16550A 00:06: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A 00:07: ttyS1 at I/O 0x2f8 (irq = 3) is a 16550A

2. Start Minicom

root@monitor:~# minicom

You should see "Initializing Modem" followed by "Welcome to Minicom".

If you get something like:

minicom: WARNING: configuration file not found, using defaults Device /dev/modem access failed: No such file or directory.

Then run:

root@monitor:~# minicom -s

Select Serial port setup > A and set correct device, i.e. /dev/ttyS0

Press Enter, then select Save setup asdfl. You should now see "Initializing Modem" or be able to run Minicom

3. If necessary, Press CTRL-A then Z to enter menu.

Select port connected to modem:

Press O > Serial port setup, press A to G for device to use and settings. Press Enter to exit.

4. You may want to turn local Echo on so that you can see your commands: From Menu (CTRL-A then Z), press E.

From Welcome screen "E1" and Enter

5. Test modem:

From Welcome screen, type "ATI" to get status:

ATISIEMENS MC35i REVISION 01.03

Type: AT+CREG? to get network status:

AT+CREG?+CREG: 0,1

+CREG: <mode>,<stat>[,<Lac>,<Ci>[,<AcT>]] 

where
<stat>
0 - not registered, ME is not currently searching a new operator to register to
1 - registered, home network
2 - not registered, but ME is currently searching a new operator to register to
3 - registration denied
4 -unknown
5 - registered, roaming
where:
<Lac> - Local Area Code for the currently registered on cell
<Ci> - Cell Id for the currently registered on cell
<AcT>: access technology of the registered network:
0 GSM
2 UTRAN
Note: <Lac>, and <Ci> and <AcT> are reported only if <mode>=2 and the
mobile is registered on some network cell.

Type: AT+CPIN? to get SIM PIN status:

AT+CPIN?+CPIN: READY

+CPIN: <code>
where:
<code> - PIN/PUK/PUK2 request status code
READY - ME is not pending for any password
SIM PIN - ME is waiting SIM PIN to be given
SIM PUK - ME is waiting SIM PUK to be given
PH-SIM PIN - ME is waiting phone-to-SIM card password to be given
PH-FSIM PIN - ME is waiting phone-to-very first SIM card password to be given
PH-FSIM PUK - ME is waiting phone-to-very first SIM card unblocking password to be given
SIM PIN2 - ME iswaiting SIM PIN2 to be given; this <code> is returned only when the last executed command resulted in PIN2 authentication failure (i.e. +CME ERROR: 17)

AT+CSQ+CSQ: 17,99

+CSQ: <rssi>,<ber>
where
<rssi> - received signal strength indication
0 - (-113) dBm or less
1 - (-111) dBm
2..30 - (-109)dBm..(-53)dBm / 2 dBm per step
31 - (-51)dBm or greater
99 - not known or not detectable
<ber> - bit error rate (in percent)
0 - less than 0.2%
1 - 0.2% to 0.4%
2 - 0.4% to 0.8%
3 - 0.8% to 1.6%
4 - 1.6% to 3.2%
5 - 3.2% to 6.4%
6 - 6.4% to 12.8%
7 - more than 12.8%
99 - not known or not detectable

6. Exit Minicom:

CTRL-A then Z then X, you should see "Resetting modem"

For more help about minicom, either do: man minicom or minicom --help.

Other useful commands/information

AT+CMGF=1AT+CMGS="+4670xxxxxx"Write message here. <ctrl+z>

Human readable signal strength

Signal strength will be reported insmsd.logif verbosity is increased to 7 in /etc/smsd.conf. If there's alot of information in /var/log/smsd/smsd.log and you can't find the right line, use grep and search for dBm.