gistfile1.c

#pragma once
#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/sleep.h>
#include "init.h"

static inline void initializeI2C(void);
void sendCommand(uint8_t data); 
uint8_t readReply(void);
uint8_t readAck(void);
void start(void);
void stop(void);
void ack(void);
void nack(void);
void clearNack(void);

static inline void initializeI2C(void) {
	DDRA |= (1 << 4) | (1 << 6) | (1 << 3);
	// pa4 scl pa6 sda
	PORTA |= (1 << 4) | (1 << 6);
	PORTA &= ~(1 << 3);
}

void sendCommand(uint8_t data) {
	volatile uint8_t i = 0;
	for (i = 0; i < 8; i++) {
		if (data & (1 << (7 - i))) {
			PORTA |= (1 << 6);
		} else {
			PORTA &= ~(1 << 6);
		}
		timer0_wait();
		PORTA ^= (1 << 4);
		timer0_wait();
		PORTA ^= (1 << 4);
		timer0_wait();
	}
	PORTA |= (1 << 6);
}

uint8_t readReply(void) {
	DDRA &= ~(1 << 6);
	PORTA |= (1 << 6);
	volatile uint8_t i = 0, data = 0;
	for (i = 0; i < 8; i++) {
		if (PINA & (1 << 6)) {
			data |= (1 << (7 - i));
		}
		timer0_wait();
		PORTA ^= (1 << 4);
		timer0_wait();
		PORTA ^= (1 << 4);
		timer0_wait();
	}
	DDRA |= (1 << 6);
	return data;
}

uint8_t readAck(void) {
	uint8_t ack = 2;
	DDRA &= ~(1 << 6);
	PORTA |= (1 << 6); // release sda
	PORTA |= (1 << 4);
	ack = PINA & (1 << 6);
	PORTA &= ~(1 << 4);
	PORTA |= (1 << 6);
	DDRA |= (1 << 6);
	if (ack != 0) { 
		PORTA |= (1 << 3);
		return 1; 
	}
	return 0;
}

void start(void) {
	PORTA |= (1 << 6);
	timer0_wait();
	PORTA |= (1 << 4);
	timer0_wait();
	PORTA &= ~(1 << 6);
	timer0_wait();
	PORTA &= ~(1 << 4);
}

void stop(void) {
	PORTA &= ~(1 << 6);
	timer0_wait();
	PORTA |= (1 << 4);
	timer0_wait();
	PORTA |= (1 << 6);
}

void ack(void) { 
	PORTA &= ~(1 << 6);
	timer0_wait();
	PORTA ^= (1 << 4);
	timer0_wait();
	PORTA ^= (1 << 4);
	PORTA |= (1 << 6);
}

void nack(void) { 
	uint8_t status = (PORTA & (1 << 3));
	PORTA |= ~(1 << 6);
	timer0_wait();
	PORTA ^= (1 << 4);
	timer0_wait();
	PORTA ^= (1 << 4);
	if (!status) { PORTA &= ~(1 << 3); };
}

void clearNack(void) {
	PORTA &= ~(1 << 3);
}