SIM900 GPRS Shield not responding to AT commands

The Sim900 shield does not respond to AT commands sent through the Arduino IDE serial monitor.

Here is my sketch

#include <SoftwareSerial.h>
SoftwareSerial Sim900Serial(2, 3); //rx and tx
void setup()
{
   Sim900Serial.begin(19200); // the GPRS baud rate
   Serial.begin(19200); // the GPRS baud rate
}
void loop()
{
   if (Sim900Serial.available())
       Serial.write(Sim900Serial.read());
   if (Serial.available())
       Sim900Serial.write(Serial.read());
}

The code compiles with no errors.

With regard to jumper settings on the Sim900, GTx is linked with D2, while GRx is linked to D3.

Arduino Uno’s pin 2,3 and GND are connected to Sim900’s Tx,Rx and GND respectively.

I have powered the Sim900 with 7V 2A from the wall socket to Vin and GND of the GPRS Shield.

I should believe that the SIM900 is working perfectly fine because i have inserted the SIM card, and when the shield is powered up and switched on, it registers a network, as it blinks every 3 seconds, and also when i call the SIM on the shield from my mobile phone, it rings with no answer.

The only response that comes from the SIM900 shield is some funny unreadable characters, they only print on the serial monitor when Sim900 is switched on then off through the PWRKEY button.

The only response that comes from the SIM900 shield is some funny unreadable characters,

That sounds like the SIM900 baud rate is not 19200. Try 9600, 38400, 57600 or 115200.

Hi tedmad,

i have almost save problem with sim808 , its responds like that almost , available always 0. its work on 9600, and its called and hangup , thats mean its work ! i spent over a week , upgrading firmware and contacting the SIM and nothing yet , its almost ruined my project and idea

0 = Autobaud. Use fix baud instead like 9600