akutester/soft/i2c.c

#include <util/delay.h>
#include <avr/io.h>
#include "i2c.h"

void scl_toggle(void) __attribute__ ((noinline));
void istart(void) __attribute__ ((noinline));
void istop(void) __attribute__ ((noinline));

void i2c_delay(void){
	_delay_us(10);
}

void scl_toggle(void){
	i2c_delay();
	SCLDDR &= ~SCL;
	i2c_delay();
	SCLDDR |= SCL;
}
void istart(void){
	SDADDR |= SDA;
	i2c_delay();
	SCLDDR |= SCL;
	i2c_delay();
}

void istop(void){
	i2c_delay();
	SCLDDR &= ~SCL;
	i2c_delay();
	SDADDR &= ~SDA;
	i2c_delay();
}

unsigned char i2cPutbyte(unsigned char b){
	signed char a;
	for(a=7;a>=0;a--){
		if(b&_BV(a)) SDADDR &= ~SDA; else SDADDR |= SDA;
		scl_toggle();
	}

	SDADDR &= ~SDA;			// leave SDL HI
	i2c_delay();
	SCLDDR &= ~SCL;	
	i2c_delay();
	while(!(SCLPIN&SCL));
	i2c_delay();		// clock back up
	b = (SDAPIN & SDA);	// get the ACK bit

	//_delay_us(15);
	SCLDDR |= SCL;			// not really ??
	return (b == 0);		// return ACK value
}

unsigned char i2cGetbyte(unsigned char notlast){
	signed char a;
	unsigned char ret=0;
	SDADDR &= ~SDA;			// make sure pullups are ativated

	for(a=7;a>=0;a--){
		i2c_delay();
		SCLDDR &= ~SCL;
		i2c_delay();
		if(SDAPIN&SDA) ret |= _BV(a);
		SCLDDR |= SCL;
	}

	i2c_delay();

	if(notlast) SDADDR |= SDA; else SDADDR &= ~SDA;
	scl_toggle();			// clock pulse
	SDADDR &= ~SDA;			// leave with SDL HI
	return ret;
}
/*
void i2cInit(void){
	set_bit( SDADDR, SDA);	// set SDA as output
	set_bit( SCLDDR, SCL);	// set SCL as output
	SDADDR &= ~SDA;		// set I/O state and pull-ups
	SCLDDR &= ~SDA;		// set I/O state and pull-ups

}*/

void i2cSend(unsigned char reg, unsigned char length, unsigned char *data, unsigned char device){ // x24/23 x22/21 20/19
	unsigned char i;
	istart();      	// do start transition
	i2cPutbyte(device); 	// send DEVICE address
	i2cPutbyte(reg);
	for(i=0;i<length;i++){
		i2cPutbyte(data[i]);
	}

	SDADDR |= SDA;		// clear data line and
	istop();		// send STOP transition
}

void i2cReceive(unsigned char reg, unsigned char length, unsigned char *data, unsigned char device){ // x24/23 x22/21 20/19
	unsigned char i;
	istart();			// do start transition
	i2cPutbyte(device);		// send DEVICE address
	i2cPutbyte(reg);
	i2c_delay();
	SCLDDR &= ~SCL;
	i2c_delay();// do a repeated START
	istart();			// transition
	i2cPutbyte(device | READ);	// resend DEVICE, with READ bit set

	for(i=0;i<length;i++){
		data[i] = i2cGetbyte((i==length-1)?0:1);
	}
	SDADDR |= SDA;			// clear data line and
	istop();			// send STOP transition
}