#include <mega16.h>
#include <delay.h>
                                            
#include "atm_i2c.h"
/*
#define PORTC_LED1	0x60	// led 1
#define PORTC_LED2	0x80	// led 2

void toggle_led1(void)
{
	if (PORTC & PORTC_LED1) {
		PORTC &= ~(PORTC_LED1);
	} else {
		PORTC |= (PORTC_LED1);
	}
}

void toggle_led2(void)
{
	if (PORTC & PORTC_LED2) {
		PORTC &= ~(PORTC_LED2);
	} else {
		PORTC |= (PORTC_LED2);
	}
}
*/



static char TWI_state = TWI_IDLE;

static char TWI_recv_buf[TWI_RECV_BUFSIZE];
static char TWI_recv_index = 0;

static char TWI_send_buf[TWI_SEND_BUFSIZE];
static char TWI_send_index = 0;
static char TWI_send_length = 0;

/*
static inline void TWI_slave_rx(char *buf, char length)
{
}

int count1 = 0;
int count2 = 0;

static inline char TWI_slave_tx(char *buf, char length)
{
	count1++;
	count2--;
	buf[0] = count1 >> 8;
	buf[1] = count1 & 0xFF;
	buf[2] = count2 >> 8;
	buf[3] = count2 & 0xFF;
	return 4;
}
*/
int twi_parse(void)
{
	switch (TWSR & TWSR_STATUS_MASK) {

	/* MASTER TRANSMIT MODE */

	/* MASTER RECEIVE MODE */

	/* SLAVE RECEIVE MODE */

	case TWSR_SR_SLA_ACK:
	case TWSR_SR_SLA_ARB_ACK:
	case TWSR_SR_GCA_ACK:
	case TWSR_SR_GCA_ARB_ACK:   
   		PORTC =  PORTC ^ 0x80;	//toggle LED2 on read    
		TWI_state = TWI_SLAVE_RX;
		TWI_recv_index = 0;
		TWCR = (TWCR & TWCR_CMD_MASK) | TWCR_TWEA;
		break;
	case TWSR_SR_SLA_DATA_ACK:
	case TWSR_SR_GCA_DATA_ACK:
		TWI_recv_buf[TWI_recv_index++] = TWDR;
		if (TWI_recv_index < TWI_RECV_BUFSIZE)
			TWCR = (TWCR & TWCR_CMD_MASK) | TWCR_TWEA;
		else
			TWCR = (TWCR & TWCR_CMD_MASK);
		break;
	case TWSR_SR_SLA_DATA_NAK:
	case TWSR_SR_GCA_DATA_NAK:
		TWCR = (TWCR & TWCR_CMD_MASK);
		break;
	case TWSR_SR_STOP:
		TWCR = (TWCR & TWCR_CMD_MASK) | TWCR_TWEA;
	//	TWI_slave_rx(TWI_recv_buf, TWI_recv_index);
		TWI_state = TWI_IDLE;
		break;

	/* SLAVE TRANSMIT MODE */

	case TWSR_ST_SLA_ACK:     
	case TWSR_ST_SLA_ARB_ACK:    
	
		TWI_state = TWI_SLAVE_TX;
 	  // 	TWI_send_length = TWI_slave_tx(TWI_send_buf, TWI_SEND_BUFSIZE);
 	   	TWI_send_length = 3;
 	   	TWI_send_index = 0;
	case TWSR_ST_DATA_ACK:  
  	    
		TWDR = TWI_send_buf[TWI_send_index++];
		if (TWI_send_index < TWI_send_length)
			TWCR = (TWCR & TWCR_CMD_MASK) | TWCR_TWEA;
		else
			TWCR = (TWCR & TWCR_CMD_MASK);
		break;
	case TWSR_ST_DATA_NAK:
	case TWSR_ST_LAST_DATA:
   		PORTC =  PORTC ^ 0x60;	//toggle LED1 on write
		TWCR = (TWCR & TWCR_CMD_MASK) | TWCR_TWEA;
		TWI_state = TWI_IDLE;
		break;

	/* MISC STATUS */

	case TWSR_GARBAGE:
		break;
	case TWSR_BUS_ERROR:
		TWCR = (TWCR & TWCR_CMD_MASK) | TWCR_TWSTO | TWCR_TWEA;
		TWI_state = TWI_IDLE;
		break;
	}
	TWCR |= TWCR_TWINT;
	
 	return TWSR & TWSR_STATUS_MASK;
}
	



void twi_init(int bitrate_khz, char addr)
{
	PORTC |= 0x03;
	TWI_state = TWI_IDLE;

	/* calculate bitrate and prescale registers (INCOMPLETE- RUN AT 100 kb/s) */
	TWBR=0x41;
	TWSR &= ~(TWSR_PRE_MASK);

	/* set slave address */
	TWAR = (addr<<1) | TWAR_TWGCE;

	/* enable TWI */
	TWCR = TWCR_TWINT | TWCR_TWEA | TWCR_TWEN | TWCR_TWIE;
}


/*
void main(void)
{
	PORTC = 0x0;
	DDRC = (PORTC_LED1 | PORTC_LED2);

	twi_init(100, 0x70);

	#asm("sei")

	while (1)
	{
 		toggle_led1();
		delay_ms(100);
		toggle_led2();
	};
}
*/