hello, I too come to acquire a shield sim900 (Seeedstudio) and I love that hen I send an sms with my laptop card activates an LED or a motor that is connected to an input or output of the map .. But being a novice I can not design my program. I saw that it was necessary to use specific AT commands for this shield: GoGprs/GoGprs.h at master · mchobby/GoGprs · GitHub
but I do not know if I should contact the arduino software or if I need to download another software .. If you had a program outline that could be useful to me thank you very much friends