AVRFreaks.net

#define FOSC 8000000 // Clock Speed
  #define BAUD 9600
  #define MYUBRR FOSC/16/BAUD-1
 
  UBRR0H = (unsigned char)(MYUBRR>>8);
  UBRR0L = (unsigned char)MYUBRR;
  //Enable receiver and transmitter */
  UCSR0B = 0x98;                                                                //Enable Rx/Tx, enable Rx interrupt
  /* Set frame format: 8data, 1stop bit */
  UCSR0C = 0x06;                                                                //8-bit, one stop, no parity, asynchronous

#define baud 9600
#define ubrr F_CPU/(16*baud)-1
void main()
{
usart_init(ubrr);
while(1)
usart_transmit('A');
}
usart_inint(uint16_t ubr)
{
UBRR0H=(unsigned char)(ubr>>Cool;
UBRR0L=(unsigned char)ubr;
UCSR0B=(1<<TXEN0)|(1<<RXEN0);
UCSR0C=(1<<UCSZ00)|(1<<UCSZ01)|(0<<UCSZ02)|(0<USBS0);

}
usart_transmit(unsigned char data)
{
while ( !( UCSR0A & (1<<UDRE0)) ) ;
UDR0 = data;

}
}

//==================================================================================================//
//                 INCLUDING HEADER FILES & OTHER GLOBAL DECLARATIONS                               //
//==================================================================================================//

#include<avr/io.h>                   // including the input/output files of avr
#include<avr/interrupt.h>            //including the interrupt files of avr
#include<avr/sfr_defs.h>            //including the special function registers
#include<util/delay.h>                //including the delay function from util directory

#define FOSC 16000000L               //clock speed of 8MHz
#define BAUD 9600                   //baud rate
#define MYUBRR ((FOSC/(16*BAUD))-1)      //defnining the USART BAUD RATE REGISTER

void transmit(unsigned char );          // function for transmitting the at command to GSM for initialization
void start_commandat(); //declaration of the function which sends 'AT' command
void USART_Init(unsigned int); //declaration of the 'USART INITIALISATION' function
unsigned char m;
//unsigned char t;
int p=0;//declaration of the required variables

//**************************************************************************************************//
//                                       MAIN PROGRAM                                               //
//**************************************************************************************************//
int main( ) //start of the program
{
     

      USART_Init(MYUBRR);//function call for the USART initialisation
   //   sei();//set the global interrupt
   
for(;;)
{
m='A';
while ( !( UCSR0A & (1<<UDRE0)) )
;
/* Put data into buffer, sends the data */
UDR0 =m;
_delay_ms(1);
            //transmit(m);
}
     

}


//////////////////////////////////////////////////////////////////////////////////////////////////////
///                    USART INITILISATION FUNCTION                                                //
//////////////////////////////////////////////////////////////////////////////////////////////////////
void USART_Init(unsigned int ubrr)
{

      UBRR0H =(unsigned char)(ubrr>>8);//setting the baud rate

      UBRR0L =(unsigned char)ubrr;//setting the baud rate

     
     
      UCSR0B = (1<<RXEN0)|(1<<TXEN0);//ENABLING THE TRANSMITTER AND RECEIVER

      UCSR0C = (0<<UMSEL01)|(0<<UMSEL00)|(0<<USBS0)|(1<<UCSZ00)|(1<<UCSZ01)|(0<<UCSZ02);//SETTING THE FRAME FORMAT WITH 8 DATA AND 1 STOP BITS
     
      UCSR0A = (1<<UDRE0);
     

}



//////////////////////////////////////////////////////////////////////////////////////////////////////
///                             TRANSMIT FUNCTION                                                //
//////////////////////////////////////////////////////////////////////////////////////////////////////
/*void transmit( unsigned char data )
{

while ( !( UCSR0A & (1<<UDRE0)) )
;

UDR0 = data;
}*/

#include <avr/io.h>
#include <stdlib.h>   // only included "free()" functionality

#define F_CPU 14745600      // Clock speed
#define BAUD 115200      // expexted transfer rate
#define MUBRR F_CPU/16/BAUD-1      // set baud rate register

void UsartInit(unsigned int ubrr){
  UBRR0H = (unsigned char) (ubrr>>8);   // set High bit to second bit of ubrr
  UBRR0L = (unsigned char) ubrr;      // set Low bit to first bit of ubrr
  UCSR0B = (1<<RXEN0) | (1<<TXEN0);   // enable Receive & Transmit circuits
  UCSR0C = (1<<USBS0) | (3<<UCSZ00);// set 2bit stop, 8bit character size
}

void UsartSend(unsigned char data){
  while ( !(UCSR0A & (1<<UDRE0)));   // wait for send buffer to be empty
  UDR0 = data;               // send data
}

unsigned char UsartReceive(void){
  while ( !(UCSR0A &(1<<RXC0)));   // wait for data reception to be complete
  unsigned char data = UDR0;
  return data;               // return received data to main()
}

void UsartFlush(void){
  unsigned char dump;            // store temp data
  while (UCSR0A &(1<<RXC0))dump = UDR0;
   // drop all incoming data to temp store until incoming data is null
  free(&dump);      // drop anything thats left by releasing the memory
}

int main(void){
  UsartInit(MUBRR);      // initialize USART for data transfer
  unsigned char gigo;      // storage for i/o of data
  for(;;){               // never ending loop
    if(DOR0){            // check for data overflow
   UsartFlush();         // and flush it out
    }
    gigo = UsartReceive();   // put input to temp storage
    UsartSend(gigo);      // send output from storage
  }
  return 0;         // end of program
}

iomx8.h:#define DOR0    3

    if(3){            // check for data overflow