Setting up GSM module (SIM800) with AVR SIM800 is a GSM module which usually used for IOT purposes. It support serial port for hardware data transfering and also it support "AT" commands. Here AVR ATmega16 is used for implementing a simple project for Send or Recieve data from the module. It can be a good project for practicing AVR microcontrollers programming. It use UART , I/O, INTERRUPT flags and function.