Hi
I want to build a system contain sensor ,Microcontroller and GSM module. I'll use SIM900 GSM module. The main idea of this project if Reed switch sensor connected I want the GSM module send an alarm message to a mobile.
Can you help how I can do this?? some steps and hints. For GSM module I read about AT commands and I knew I must desire if I want it receiver or sender.
Any suggestions it's will be better. Thank you