A couple of days ago I've bought a RPI SIM900 GSM/GPRS ADD-ON V1.0 and I'm struggling to make it work since then.
I have disabled the service that used the /dev/ttyAMA0 serial port as suggested.
Still when I try to use minicom to send some AT commands to the addon, it just hangs.
Here is the command I use: minicom -b 9600 -o -D /dev/ttyAMA0
I've also tried to use the C library you provided, but it also does not seem to work.
Any help would be appreciated.