#include <avr/io.h>
#include <util/delay.h>
#include "USI_I2C_Master.h"

void I2CinitM(){
	//activate pullups
	PORT_USI |= 1<<USI_SDA;
	PORT_USI |= 1<<USI_SCL;

	//SDA and SCL as OUTPUT
	DDR_USI |= 1<<USI_SCL;
	DDR_USI |= 1<<USI_SDA;

	//prepare dataregister
	USIDR = 0xFF;
	//Interrupts off, TWI-Mode, Softwarestrobe
	USICR = 0;
	USICR |= 1<<USIWM1 | 1<<USICS1;
	USISR = I2C8BIT;
}

uint8_t I2Ctransfer(uint8_t config){
	USISR = config;
	config = 0;
	config |= (1<<USIWM1) | (1<<USICS1) | (1<<USICLK) | (1<<USITC);

	do{
		_delay_us(I2C_T2);
		//positive CLK
		USICR = config;
		while( !(PIN_USI & (1<<USI_SCL)) );
		_delay_us(I2C_T4);
		//negative CLK
		USICR = config;
	}while( !(USISR & (1<<USIOIF)) );

	_delay_us(I2C_T2);
	config = USIDR;
	USIDR = 0xFF;

	DDR_USI |= (1<<USI_SCL);

	return config;
}

uint8_t I2Cstart(uint8_t address, uint8_t mode){
	//Release SCL for START or repeated START
	PORT_USI |= 1<<USI_SCL;
	//wait for SCL to become high
	while( !(PIN_USI & (1<<USI_SCL)) ){
		;
	}
#ifdef I2C_FAST_MODE
	_delay_us(I2C_T4);
#else
	_delay_us(I2C_T2);
#endif

	//Start Condition
	PORT_USI &= ~(1<<USI_SDA);
	_delay_us(I2C_T4);
	PORT_USI &= ~(1<<USI_SCL);
	PORT_USI |= 1<<USI_SDA;

//Send address and R/!W
	//SCL low
	PORT_USI &= ~(1<<USI_SCL);
	USIDR = address<<1;
	USIDR |= mode & (1<<0);
	I2Ctransfer(I2C8BIT);

	//check for (N)ACK
	DDR_USI &= ~(1<<USI_SDA);
	if( !I2Ctransfer(I2C1BIT))
		return 1;	//ACK
	else
		return 0;	//NACK
}

uint8_t I2Cwrite(uint8_t *data, uint8_t bufsize){
	while(bufsize){
		//SCL low
		PORT_USI &= ~(1<<USI_SCL);
		//setup data
		USIDR = *data;
		I2Ctransfer(I2C8BIT);

		//check for (N)ACK
		DDR_USI &= ~(1<<USI_SDA);
		if(I2Ctransfer(I2C1BIT))
			return 0;	//NACK

		++data;
		--bufsize;
	}
	return 1;
}

uint8_t I2Cread(uint8_t *data, uint8_t bufsize){
	while(bufsize){
		DDR_USI &= ~(1<<USI_SDA);
		*data = I2Ctransfer(I2C8BIT);

		//send (N)ACK
		if(bufsize > 1)
			USIDR = 0xFF;
		else
			USIDR = 0x00;
		I2Ctransfer(I2C1BIT);

		++data;
		--bufsize;
	}
	return 1;
}

void I2Cstop(){
	//SDA low
	PORT_USI &= ~(1<<USI_SDA);
	//SCL high
	PORT_USI |= 1<<USI_SCL;
	while( !(PIN_USI & (1<<USI_SCL)) ){
		;
	}
	_delay_us(I2C_T4);
	PORT_USI |= 1<<USI_SDA;
	_delay_us(I2C_T2);
}