Sim900A GSM/GPRS module and sending and receiving SMS

the version of this product is 3.8.2.
the GSM module with GPRS connectivity and sending and receiving sms sim900a features two power supply inputs, supporting a vcc5 interface at 5v and a vcc4 interface between 3.5-5 volts. this module can communicate with a microcontroller via uart. this module supports power-off mode and software reset.

Documents:

schematic of the sim900a module

sim900a-board code example

wiring guide for the sim900a module