Somehow I found that the Arduino pin9 is used to turn on and off the shield. Pin3 controls the DTR (in case you put it on sleep mode, you must write low on pin3 and then the Serial Comunication re-estabilishes for 50us, then you wake it up). What about the others? Where can I find ?
I can't remember where I found the connections between arduino pins and SIM900 thru the shield. I want to use the RI pin of SIM900 to attach a interrupt whenever the SIM900 receives a SMS but I don't have an idea which pin in Arduino is conected to RI pin on SIM900.
Does somebody know all the Arduino pins that are connected to the SIM900 and their functions? I downloaded icommsat diagram but it is not very easy to understand.