Introduction - If you have any usage issues, please Google them yourself
SIM900A#include <avr/io.h>
#include <avr/signal.h>
#include <avr/interrupt.h>
#include <stdlib.h>
#include <inttypes.h>
#define sbi(sfr,bit) (_SFR_BYTE(sfr)|=_BV(bit))
#define cbi(sfr,bit) (_SFR_BYTE(sfr)&=~_BV(bit