ICOMSAT 1.1 GPRS Shield - AT Commands


I have recently purchased an ICOMSAT 1.1 GPRS /GSM Shield, based on the SIM900 chip.
This is exactly the one I’ve purchased - http://www.ebay.co.uk/itm/251201741345?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

I’ve been playing around with it for a few days and have managed to get SMS to work using the GSM Library here - http://code.google.com/p/gsm-shield-arduino/

However - I am keen to keep my code as lean as possible, so was hoping to send/receive data to the modem using AT commands.
But everything I try, doesn’t work.

What I would like to try is to talk directly to the modem using a terminal emulator, eg - Putty. But when I think I have everything right, I just get gibberish back, or sometimes, nothing at all.

I’m hoping someone has used this modem before and can shed some light - I’d specifically appreciate any code that will help me talk to this via putty.

here is the code I am using -

#include <SoftwareSerial.h>

SoftwareSerial mySerial(4, 5); // RX, TX  - There are jumpers on the modem and the settings here reflect the jumper positioning

void setup()  
   // Open serial communications and wait for port to open:
   while (!Serial) {
     ; // wait for serial port to connect. Needed for Leonardo only

   Serial.println("Goodnight moon!");

   // set the data rate for the SoftwareSerial port
   mySerial.println("Hello, world?");

void loop() // run over and over
   if (mySerial.available())
   if (Serial.available())

Hej there,

I would like to guess 2 cases:

  • no respond from the board: RX-TX is wired wrong, change the pins
  • crap as respond from the board: Baudrate (9600) is wrong, try 19200 and 57600, even try the hardware serial at your MC first.

Regards so far, Bastian