CPE326_RTC

CPE326_RTC.c

#include <stdio.h>
#include <avr/io.h>
#define F_CPU 8000000UL
#include <util/delay.h>

typedef struct
{
	uint8_t sec;
	uint8_t min;
	uint8_t hour;
	uint8_t weekDay;
	uint8_t date;
	uint8_t month;
	uint8_t year;
} rtc_t;

rtc_t DS1307_Read() 
{
	TWCR = (1<<TWINT)|(1<<TWSTA)|(1<<TWEN);	// send start bit
	while (!(TWCR & (1<<TWINT))); // wait until start bit is send
	
	TWDR = 0xD0;	// send address (in write mode)
	TWCR = (1<<TWINT) | (1<<TWEN);
	while (!(TWCR & (1<<TWINT)));
	
	TWDR = 0x00;	// set read pointer to address 0
	TWCR = (1<<TWINT) | (1<<TWEN);
	while (!(TWCR & (1<<TWINT)));
	
	TWCR = (1<<TWINT)|(1<<TWEN)|(1<<TWSTO);	// send stop bit
	
	rtc_t currentTime;
	
	TWCR = (1<<TWINT)|(1<<TWSTA)|(1<<TWEN);	// send start bit
	while (!(TWCR & (1<<TWINT))); // wait until start bit is send
	
	TWDR = 0xD1;	// send address (in read mode)
	TWCR = (1<<TWINT) | (1<<TWEN);
	while (!(TWCR & (1<<TWINT)));
	
	TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWEA);
	while (!(TWCR & (1<<TWINT)));
	currentTime.sec = ((TWDR & 0x70) >> 4) * 10 + (TWDR & 0x0F);
	
	TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWEA);
	while (!(TWCR & (1<<TWINT)));
	currentTime.min = ((TWDR & 0x70) >> 4) * 10 + (TWDR & 0x0F);
	
	TWCR = (1<<TWINT) | (1<<TWEN);
	while (!(TWCR & (1<<TWINT)));
	currentTime.hour = ((TWDR & 0x30) >> 4) * 10 + (TWDR & 0x0F);
	
	TWCR = (1<<TWINT)|(1<<TWEN)|(1<<TWSTO);	// send stop bit
	
	return currentTime;
}

int main(void)
{
	TWBR = 32;				// 100Khz at 8Mhz Fcpu
	TWCR |= (1 << TWEN);	// enable TWI module

	// Enable RX and TX module
	UCSR0B |= (1 << RXEN0) | (1 << TXEN0);
	// Set data to 8bit
	UCSR0C |= (1 << UCSZ01) | (1 << UCSZ00);
	// Set baud rate to 9600 at 8MHz
	UBRR0 = 51;
	
	int i;
	char buffer[32];
    while (1) 
    {
		rtc_t currentTime = DS1307_Read();
		sprintf(buffer, "%d:%d:%d\r", currentTime.hour, currentTime.min
			, currentTime.sec);
		
		// wait until transmit buffer ready
		i = 0;
		while (buffer[i] != '\0')
		{	
			while (!(UCSR0A & (1 << UDRE0)));
			UDR0 = buffer[i];
			i++;
		}
		
		_delay_ms(1000);
    }
}