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/* twi_master.c */
#include "twi_master.h"

#include <n/avr/rs232/rs232.h>
#include <avr/twi.h>
#include <avr/io.h>
#include <avr/signal.h>
#include <string.h>

enum
{
    TWI_SUCCESS,
    TWI_BUSY,
    TWI_FREE,
    TWI_ECHEC
};

#define TWI_DEBUG(x) rs232_putc (x)

#define NB_ITER_WAIT 40000
#define NB_RETRY 5

static uint8_t *buffer;
static uint8_t twi_dest_addr;
static uint8_t twi_len;
static uint8_t twi_idx;
static uint8_t twi_nb_retry;
volatile uint8_t twi_state = TWI_FREE;

#define SYSCLK 14745600UL

/* compteur 10 ms pour attente du bus 40 000 iterations */
/* compteur x essais y ms secondes d'attende */
void 
twi_master_init (void)
{
    /* initialize TWI clock: 100 kHz clock, TWPS = 0 => prescaler = 1 */
#if defined(TWPS0)
    TWSR = 0;
#endif
    TWBR = (SYSCLK / 100000UL - 16) / 2;
    TWCR = _BV (TWEN) | _BV (TWIE);
}

int8_t 
twi_is_finished ()
{
    if (twi_state == TWI_SUCCESS || twi_state == TWI_ECHEC)
	return 1;
    else
	return 0;
}

int8_t 
twi_master_send (uint8_t addr, uint8_t *data, uint8_t len)
{
    if (twi_state == TWI_FREE)
      {
	TWI_DEBUG ('a');
	twi_state = TWI_BUSY;
	twi_nb_retry = 0;
	twi_dest_addr = addr & 0xfe;
	twi_len = len;
	buffer = data;
	/* envoie du start */
	TWCR |= _BV(TWSTA);
	TWCR |= _BV(TWINT);
	return 0;
      }
    else 
      {
	TWI_DEBUG ('x');
	return -1;
      }
}

int8_t
twi_master_read (uint8_t addr, uint8_t *data, uint8_t len)
{
    if (twi_state == TWI_FREE)
      {
	TWI_DEBUG ('a');
	twi_state = TWI_BUSY;
	twi_nb_retry = 0;
	twi_dest_addr = addr | 0x01;
	twi_len = len;
	buffer = data;
	//TWCR &= ~_BV (TWSTO);
	TWCR |= _BV(TWSTA) | _BV (TWINT);
	return 0;
      }
    else
	return -1;
}

SIGNAL (SIG_2WIRE_SERIAL)
{ 
    TWI_DEBUG ('y');
    switch (TW_STATUS)
      {
	/* Master */
      case TW_START: 
      case TW_REP_START:
	/* start transmis, on envoie l'adresse */
	TWI_DEBUG ('d');
	TWCR &= ~ (_BV (TWSTA) |  _BV (TWSTO) | _BV (TWINT));
	TWDR = twi_dest_addr;
	twi_idx = 0;
	break;
      case TW_MT_ARB_LOST: /* valable pour le receiver aussi */
	/* todo */
	TWI_DEBUG ('e');
	break;
	/* Master Transmitter */
      case TW_MT_DATA_ACK:
      case TW_MT_SLA_ACK: 
	/* slave ok 
	 * On envoi des donn�es si il en reste
	 */
	if (twi_idx < twi_len) 
	  {
	    TWI_DEBUG ('f');
	    TWDR = buffer[twi_idx ++];
	  }
	else
	  {
	    TWCR  |= _BV (TWSTO);
	    TWI_DEBUG ('g');
	    twi_state = TWI_SUCCESS;
	  }
	break;
      case TW_MT_SLA_NACK:
	/* le slave ne repond plus 
	 * on essaye NB_RETRY avant d'arreter 
	 */
	if (twi_nb_retry  < NB_RETRY)
	  {
	    TWI_DEBUG ('h');
	    TWCR |= _BV (TWSTA);
	    twi_nb_retry ++;
	  }
	else
	  {
	    TWI_DEBUG ('i');
	    TWCR  |= _BV (TWSTO);
	    twi_state = TWI_ECHEC;
	  }
	break;
      case TW_MT_DATA_NACK:
	/* le slave ne veut plus de donn�e */
	    TWI_DEBUG ('j');
	TWCR  |= _BV (TWSTO);
	twi_state = TWI_SUCCESS;
	break;
	/* Master Receiver */
      case TW_MR_SLA_ACK:
	TWI_DEBUG ('p');
	if (twi_len > 1) /* on recoit plusieurs octet */
	  {
	    TWI_DEBUG ('k');
	    TWCR |= _BV (TWEA);
	  }
	break;
      case TW_MR_SLA_NACK:
	if (twi_nb_retry < NB_RETRY)
	  {
	    TWI_DEBUG ('l');
	    TWCR |= _BV (TWEA);
	  }
	else 
	  {
	    TWI_DEBUG ('m');
	    TWCR |= _BV (TWSTO);
	    twi_state = TWI_ECHEC;
	  }
	break;
      case TW_MR_DATA_ACK:
	buffer[twi_idx ++] = TWDR;
	TWI_DEBUG ('n');
	if (twi_idx == (twi_len - 1)) 
	    TWCR &= ~ _BV (TWEA);
	break;
      case TW_MR_DATA_NACK: /* dernier byte */
	twi_state = TWI_SUCCESS;
	TWI_DEBUG ('o');
	buffer[twi_idx ++] = TWDR;
	TWCR |= _BV (TWSTO);
	break;
      }
    TWCR |= _BV (TWINT);
}