/*
 *  circumference.c
 *  
 *  Main program for Circumference Cycles Sensor Egg
 *
 *
 *  LED array into PORT B
 *  Data pins into PORT C
 *  Usart and status LEDs in PORTD
 */

#define F_CPU 1000000UL /* avr on-chip oscillator speed is 1mhz */

#include <stdint.h>
#include <stdlib.h>
#include <util/delay.h> 
#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/pgmspace.h>
#include <avr/sleep.h>
#include <util/twi.h>

#include <uart.h>


#define TWI_SLA_24CXX	0xC0
#define PAGE_SIZE 8
#define MAX_ITER 200
/*
 * Saved TWI status register, for error messages only.  We need to
 * save it in a variable, since the datasheet only guarantees the TWSR
 * register to have valid contents while the TWINT bit in TWCR is set.
 */
uint8_t twst;


void init_twi(void)
{
	/* initialize TWI clock: 100 kHz clock, TWPS = 0 => prescaler = 1 */
	TWSR = 0;
	TWBR = 10;			/* smallest TWBR value, see note [5] */
}







/*
 *
 * Read "len" bytes from EEPROM starting at "eeaddr" into "buf".
 *
 * This requires two bus cycles: during the first cycle, the device
 * will be selected (master transmitter mode), and the address
 * transfered.  Address bits exceeding 256 are transfered in the
 * E2/E1/E0 bits (subaddress bits) of the device selector.
 *
 * The second bus cycle will reselect the device (repeated start
 * condition, going into master receiver mode), and transfer the data
 * from the device to the TWI master.  Multiple bytes can be
 * transfered by ACKing the client's transfer.  The last transfer will
 * be NACKed, which the client will take as an indication to not
 * initiate further transfers.
 */
int
ee24xx_read_bytes(uint16_t eeaddr, int len, uint8_t *buf)
{
  uint8_t sla, twcr, n = 0;
  int rv = 0;

  /* patch high bits of EEPROM address into SLA */
  sla = TWI_SLA_24CXX | (((eeaddr >> 8) & 0x07) << 1);

  /*
   * Note [8]
   * First cycle: master transmitter mode
   */
  restart:
  if (n++ >= MAX_ITER)
    return -1;
  begin:

  TWCR = _BV(TWINT) | _BV(TWSTA) | _BV(TWEN); /* send start condition */
  while ((TWCR & _BV(TWINT)) == 0) ; /* wait for transmission */
  switch ((twst = TW_STATUS))
    {
    case TW_REP_START:		/* OK, but should not happen */
    case TW_START:
      break;

    case TW_MT_ARB_LOST:	/* Note [9] */
      goto begin;

    default:
      return -1;		/* error: not in start condition */
				/* NB: do /not/ send stop condition */
    }

  /* Note [10] */
  /* send SLA+W */
  TWDR = sla | TW_WRITE;
  TWCR = _BV(TWINT) | _BV(TWEN); /* clear interrupt to start transmission */
  while ((TWCR & _BV(TWINT)) == 0) ; /* wait for transmission */
  switch ((twst = TW_STATUS))
    {
    case TW_MT_SLA_ACK:
      break;

    case TW_MT_SLA_NACK:	/* nack during select: device busy writing */
				/* Note [11] */
      goto restart;

    case TW_MT_ARB_LOST:	/* re-arbitrate */
      goto begin;

    default:
      goto error;		/* must send stop condition */
    }

  TWDR = eeaddr;		/* low 8 bits of addr */
  TWCR = _BV(TWINT) | _BV(TWEN); /* clear interrupt to start transmission */
  while ((TWCR & _BV(TWINT)) == 0) ; /* wait for transmission */
  switch ((twst = TW_STATUS))
    {
    case TW_MT_DATA_ACK:
      break;

    case TW_MT_DATA_NACK:
      goto quit;

    case TW_MT_ARB_LOST:
      goto begin;

    default:
      goto error;		/* must send stop condition */
    }

  /*
   * Note [12]
   * Next cycle(s): master receiver mode
   */
  TWCR = _BV(TWINT) | _BV(TWSTA) | _BV(TWEN); /* send (rep.) start condition */
  while ((TWCR & _BV(TWINT)) == 0) ; /* wait for transmission */
  switch ((twst = TW_STATUS))
    {
    case TW_START:		/* OK, but should not happen */
    case TW_REP_START:
      break;

    case TW_MT_ARB_LOST:
      goto begin;

    default:
      goto error;
    }

  /* send SLA+R */
  TWDR = sla | TW_READ;
  TWCR = _BV(TWINT) | _BV(TWEN); /* clear interrupt to start transmission */
  while ((TWCR & _BV(TWINT)) == 0) ; /* wait for transmission */
  switch ((twst = TW_STATUS))
    {
    case TW_MR_SLA_ACK:
      break;

    case TW_MR_SLA_NACK:
      goto quit;

    case TW_MR_ARB_LOST:
      goto begin;

    default:
      goto error;
    }

  for (twcr = _BV(TWINT) | _BV(TWEN) | _BV(TWEA) /* Note [13] */;
       len > 0;
       len--)
    {
      if (len == 1)
	twcr = _BV(TWINT) | _BV(TWEN); /* send NAK this time */
      TWCR = twcr;		/* clear int to start transmission */
      while ((TWCR & _BV(TWINT)) == 0) ; /* wait for transmission */
      switch ((twst = TW_STATUS))
	{
	case TW_MR_DATA_NACK:
	  len = 0;		/* force end of loop */
	  /* FALLTHROUGH */
	case TW_MR_DATA_ACK:
	  *buf++ = TWDR;
	  rv++;
	  break;

	default:
	  goto error;
	}
    }
  quit:
  /* Note [14] */
  TWCR = _BV(TWINT) | _BV(TWSTO) | _BV(TWEN); /* send stop condition */

  return rv;

  error:
  rv = -1;
  goto quit;
}



// initializes Timer 2 to send PWM to the midi converter

void init_timer(void)
{ 
	// set timer 2 to Fast PWM
	TCCR2A |= (1 << WGM20) | (1 << WGM21);

	// non-inverted
	TCCR2A |= (1 << COM2A1);
	// | (1 << COM2A0);

	// set prescaler to 1/32
	//TCCR2B |= (1 << CS21)
    //	    | (1 << CS20);
	
	OCR2A = 0;

	// reset timer-compare register
	TCNT2 = 0;
}


/*
 *
 */
int main( void )
{
  	int rv;
  	uint8_t b[1];
	int c;
	//float d;

	init_uart();
	init_twi();
	//init_timer();

	//unsigned char compass_value;

	DDRB |= (1 << 0);		// SET PD2 to output for power LED

	while(1)
	{
		
		//PORTB &= ~(1 << 0);		// Turn on Power LED
		//_delay_ms(500);
		//compass_value = read_ad();
		//PORTB |= (1 << 0);		// Turn off Power LED
		//_delay_ms(500);
		//d = 360*(((float)b[0] / 255.0));
		//OCR2A = (b[0] / 2);
		//OCR2A = b[0];
		//uart_put_int( b[0] );

		// divide by two for output of 0-127
		rv = ee24xx_read_bytes(1, 1, b);
		b[0] = b[0] / 2;

		if (b[0] != c)
		{
			c = b[0];
			uart_put_int( c );
			_delay_ms(200);
		}
		
		//uart_put_PSTR( PSTR("hi\n") );
		//_delay_ms(200);

	}
}