#include "project.h"

/*
 * VGA 640x480 mode timings are
 *
 * 48 640 16 96
 * 10 480 33  2
 *
 * at 25.175 Hz
 *
 */

/*
 * Two bytes are shown per video frame one starting at
 * scanline 70, the other at 255, and there are 15
 * scanlines between bits.
 *
 */

#define SL_BYTE_1_START 70
#define SL_BIT    15
#define SL_BYTE_2_START 255

#undef PAD
#undef EX

#define SL_ON(byte,bit) ((SL_BYTE_ ## byte ## _START) + (SL_BIT * (bit)))
#define SL_OFF(byte,bit) (SL_ON(byte,bit) + 1)


#define SEND_BIT(byte,bit,data) \
  case SL_ON(byte,bit): \
  timex_led((data) & 1); \
  break; \
  case SL_OFF(byte,bit): \
  timex_led(1); \
  break

#define SEND_BIT_SHIFT(byte,bit,data) \
  case SL_ON(byte,bit): \
  timex_led((data) & 1); \
  data>>=1; \
  break; \
  case SL_OFF(byte,bit): \
  timex_led(1); \
  break

#define SEND_BYTE(byte, start, data) \
  SEND_BIT(byte,0,start); \
  SEND_BIT_SHIFT(byte,1,data); \
  SEND_BIT_SHIFT(byte,2,data); \
  SEND_BIT_SHIFT(byte,3,data); \
  SEND_BIT_SHIFT(byte,4,data); \
  SEND_BIT_SHIFT(byte,5,data); \
  SEND_BIT_SHIFT(byte,6,data); \
  SEND_BIT_SHIFT(byte,7,data); \
  SEND_BIT_SHIFT(byte,8,data)



/*
 * We ignore the horizontal front/back/sync and drive the system timer at
 * the horizontal sync frequency of 31.46875kHz or as close as we can manage
 */


#define BUFFER_SIZE 512

#define TIMEX_BANK GPIOB
#define TIMEX_GPIO GPIO9

ring_t timex_ring;
static uint8_t timex_ring_buf[BUFFER_SIZE];


static inline void timex_led (int v)
{
  if (v)
    gpio_set (TIMEX_BANK, TIMEX_GPIO);
  else
    gpio_clear (TIMEX_BANK, TIMEX_GPIO);
}


#define SYNCS 200
typedef enum  {
  STATE_MAGIC1,
  STATE_MAGIC2,
  STATE_MAGIC3,
  STATE_MAGIC4,
  STATE_IDLE,
  STATE_SYNC1,
  STATE_SYNC2,
  STATE_PACKET_HEADER,
  STATE_PACKET_DATA,
  STATE_PACKET_PAD,
  STATE_PACKET_RECOVERY,

} Timex_state;



static int get_data (uint8_t *start, uint8_t *data)
{
  static Timex_state state = STATE_MAGIC1;
  static unsigned len;
  static unsigned pad;


  *start = 0;

  switch (state) {
  case STATE_MAGIC1:
    if (ring_empty (&timex_ring))
      return 1;
    
  case STATE_IDLE:
    if (ring_empty (&timex_ring))
      return 1;

    state = STATE_SYNC1;
    len = SYNCS;
    break;

  case STATE_SYNC1:
    *data = 0x55;
    len--;

    if (!len) state = STATE_SYNC2;

    break;

  case STATE_SYNC2:
    *data = 0xaa;
    state = STATE_PACKET_HEADER;
    break;

  case STATE_PACKET_HEADER:
    if (ring_read_byte (&timex_ring, data)) {
      /*No more data*/
      state = STATE_MAGIC1;
      return 1;
    }
    len = *data -1 ;
    state = STATE_PACKET_DATA;
#ifdef PAD
    pad =(*data &1);
#else
    pad=0;
#endif
    break;

  case STATE_PACKET_DATA:
    ring_read_byte (&timex_ring, data);
    len--;

    if (!len) {
#ifdef PAD
      len = 20;
#else
      len = 10;
#endif

      if (pad)
      state = STATE_PACKET_PAD;
	else 
      state = STATE_PACKET_RECOVERY;
    }

    break;

  case STATE_PACKET_PAD:
	*data=0x00;
      state = STATE_PACKET_RECOVERY;
	break;


  case STATE_PACKET_RECOVERY:
    *start = 1;
    *data = 0xff;
    len--;

    if (!len) state = STATE_PACKET_HEADER;

    break;
  }


  return 0;
}

void timex_tick (void)
{
  static unsigned line = 0;
  static uint8_t data, start;


  switch (line) {
  case (SL_BYTE_1_START-2):
    if (get_data (&start, &data)) {
      line = 0;
      return;
    }
    break;

    SEND_BYTE (1, start, data);

#ifdef PAD
  case (SL_BYTE_2_START-2):
    if (get_data (&start, &data)) {
      line = 0;
      return;
    }
    break;
    SEND_BYTE (2, start, data);
#endif


  }


  line++;

  if (line == 525)
    line = 0;
}

#ifdef EX
uint8_t ex[]={
#include "/root/projects/timex_datalink/datalink-1.0.1/fish.h"
};
#endif

	


void
timex_init (void)
{
  ring_init (&timex_ring, timex_ring_buf, sizeof (timex_ring_buf));
#ifdef EX
  ring_write(&timex_ring,ex,sizeof(ex));
#endif
  gpio_set_mode (TIMEX_BANK, GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_OPENDRAIN, TIMEX_GPIO);


  timex_led (1);
}