couple AVR UART examples

mega324

/*
 * mega324_UART.c
 *
 * Created: 12/28/2011 10:39:01 PM
 *  Author: Galen
 */ 

#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/power.h>

#define F_CPU 20000000
#define USART_BAUDRATE 9600
#define BAUD_PRESCALE (((F_CPU / (USART_BAUDRATE * 16UL))) - 1) 

void sendString(uint8_t *data);
void sendByte(uint8_t data);
uint8_t recieveByte();
void initUART1();



int main(void)
{
  //uint8_t *msg = "hello!\r\n";
	cli();
	power_all_disable();
	power_usart1_enable();
	initUART1();
	unsigned char byte = 0;
	//for(byte = 255;byte == 0;byte--);

	sendByte('T');
	sendByte('e');
	sendByte('s');
	sendByte('t');
	sendByte('\n');
	//return 1;
	
	//sendString(msg);
	while(1)
	{
	byte = recieveByte();
	sendByte(byte);
	}

}

void initUART1()
{
	UCSR1B |= (1<<RXEN1) | (1<<TXEN1);
	UCSR1C |= (1<<UCSZ10) | (1<<UCSZ11);
	UBRR1H = (BAUD_PRESCALE>>8);
	UBRR1L = BAUD_PRESCALE;
}

void sendByte(uint8_t data)
{
	while ((UCSR1A & (1<<UDRE1)) == 0);
	UDR1 = data;
	return;
}

void sendString(uint8_t *data)
{
	while(*data)
	{
		sendByte(*data);
		data++;
	}		
}

uint8_t recieveByte()
{
	while ((UCSR1A & (1<<RXC1)) == 0);
	return UDR1;
}

mega328

/* CC-BY-NC-SA */

#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/power.h>

#define F_CPU 1000000
#define BAUD 9600
// calculate the prescale value (should be optimized at compile time)
#define PRESCALE (((F_CPU / (BAUD * 16UL))) - 1)


void sendString(uint8_t *data);
void sendByte(uint8_t data);
uint8_t recieveByte();
void initUART();


int main(void)
{
  initUART();
	unsigned char byte = 42; // B

	sendByte('T');
	sendByte('e');
	sendByte('s');
	sendByte('t');
	sendByte('\n');
	
	while(1) { // echo whatever we get
	    byte = recieveByte();
    	sendByte(byte);
	}

}

void initUART()
{
	UBRR0H = (PRESCALE>>8);
	UBRR0L = PRESCALE;
    // enable TX and RX hardware
	UCSR0B |= (1<<RXEN0) | (1<<TXEN0);
	UCSR0C |= (1<<USBS0);  // rest are defaults
}

void sendByte(uint8_t data)
{                                   
    // wait for clear...
	while (!(UCSR0A & (1<<UDRE0))); 
	UDR0 = data;
	return;
}

void sendString(uint8_t *data)
{
	while(*data)
	{
		sendByte(*data);
		data++;
	}		
}

uint8_t recieveByte()
{
	while ((UCSR0A & (1<<RXC0)) == 0);
	return UDR0;
}

tiny2313

#include <avr/io.h>

#define F_CPU 8000000
#define BAUD 9600
#define PRESCALE (((F_CPU/(BAUD * 16UL))) -1)

void initUART();
void transmitByte(unsigned char data);
void transmitString(unsigned char *data);
unsigned char receiveByte();

int main()
{
  unsigned char byte;

	initUART();
    transmitByte(12); //New page
	transmitString("Welcome to the AVR console\n\r");
	transmitString(">");
	
	while(1)
	{
		byte = receiveByte();
		transmitByte(byte);
	}
}

void initUART()
{
	UBRRH = (PRESCALE>>8);
	UBRRL = PRESCALE;
	UCSRB |= (1<<RXEN) | (1<<TXEN) ;
	UCSRC |= (1<<UCSZ1) | (1<<UCSZ0);
}

void transmitByte(unsigned char data)
{
	while(!(UCSRA & (1<<UDRE)));
	UDR = data;
}

void transmitString(unsigned char *data)
{
	while(*data)
	{
		transmitByte(*data);
		data++;
	}
}

unsigned char receiveByte()
{
	while(!(UCSRA & (1<<RXC)));
	return UDR;
}