GPRS Shield Not Communicating

Products & Technology Shields
13

I received a few GPRS shields today, none of which seemed to be working, until after struggling for a while I observed the following:

  1. The default speed was not set at 19200 but 9600, as soon as I changed the line

mySerial.begin(19200);

into

mySerial.begin(9600);

I started to get readable replies. You can set the speed to 19200 with the command AT+IPR=19200, but the you have to change your code again.
You could also use AT+IPR=0 which makes the SIM900 automagically adjust the speed. At speeds of 19200 or more the Arduino serial monitor may garble up some characters.

  1. Oddly enough the first AT sent to the modem mustbe in uppercase. Following AT commands can be sent in lowercase.

  2. After each AT command you must send a Carriage Return (a newline is not recognised as the end of a command)

  3. The wiki page explicitely states that for a Stalker V2.0 board the OK_READ Jumper must be removed. This is also the case for the Stalker V2.1

  4. The wiki page states that you need to have a SIM card without PIN code. This is not true. If the SIM has a PIN you can enter the pin with the command

AT CPIN=xxxx (where XXXX is the PIN)

  1. The GPRS shield needs 5V. So if you use the UARTSBEE on a Stalker board, make sure the switch is set to 5V.

Hope this helps some of you out there to make things work.