SIM 900 problem

Official Hardware Retired GSM Shield
1

Hello,

i have a problem with coummunicating with SIM900 over HW Serial port and Software library,
modem is not replying or recieving AT commands from port.

I have this module SIM900

This one works perfectly with HW Serial and Software library SIM900 big one

Anybody have solution?

2

Hi
I found these tutorials very usefull for the SIM900
http://www.cooking-hacks.com/gprs-quadband-module-sim900-for-arduino