perlmodem

#!/usr/bin/perl

# get_gsm_signal.pl
# jp - 01082013
# Connects to wavecom gsm modem on /dev/ttyS0.
# Issues AT+CSQ command to get RSSI and BER
# Outputs ready for collection by cacti.

use Device::Modem;

my $modem = new Device::Modem( port => '/dev/ttyS0' );

if( $modem->connect( baudrate => 9600 ) ) {
  } else {
      print "sorry, no connection with serial port!\n";
  }

# Reset the modem, then send in the AT commands.
# Use the builtin carriage return function - or have a bad time.

$modem->atsend( 'AT+CSQ' . Device::Modem::CR );
$csq = $modem->answer();

# Some wrangling - its content over style I'm afraid

$csq =~ s/OK//g;

# Remove all newline chars to get sensible output.
$csq =~ s/\r\n//g;

$csq =~ s/^\+CSQ\:\ //;
my($sig, $ber) = split(/,/, $csq, 2);

# Finally output in a format that cacti expects

print "SIG:$sig BER:$ber\n";