#include "project.h"

#define SHT20_ADDRESS 0x40

#define TRIGGER_TEMP_MEASURE_HOLD             0xE3
#define TRIGGER_HUMD_MEASURE_HOLD             0xE5
#define TRIGGER_TEMP_MEASURE_NOHOLD           0xF3
#define TRIGGER_HUMD_MEASURE_NOHOLD           0xF5
#define WRITE_USER_REG                        0xE6
#define READ_USER_REG                         0xE7
#define SOFT_RESET                            0xFE


void
sht20_reset (void)
{

  i2cb_start_transaction (SHT20_ADDRESS, I2C_WRITE);
  i2cb_send_data (SOFT_RESET);
  i2cb_stop();
  delay_ms (100);
  printf ("$SNTHR\n");
}


char *
sht20_temp_s (void)
{
  u8 h, l, c, s;
  s32 t, tf;
  float f;
  static char ret[8];

  i2cb_start_transaction (SHT20_ADDRESS, I2C_WRITE);
  i2cb_send_data (TRIGGER_TEMP_MEASURE_NOHOLD);
  delay_ms (100);
  i2cb_start_transaction (SHT20_ADDRESS, I2C_READ);

  h = i2cb_read (0);
  l = i2cb_read (0);
  c = i2cb_read (1);

  i2cb_stop();

  t = h;
  t <<= 8;
  t |= l & 0xfc;

  f = t;
  f /= 65536.;
  f *= 175.72;
  f -= 46.85;

  f *= 100.;

  t = (s32) (f + .5);

  ret[0] = '-';

  if (t >= 0)
    s = 1;
  else {
    s = 0;
    t = -t;
  }

  tf = t % 100;
  t = t / 100;

  sprintf (&ret[1], "%ld.%02ld", t, tf);

  return &ret[s];

}

char *
sht20_humid_s (void)
{
  u8 h, l, c;
  u32 t, tf;
  float f;
  static char ret[8];

  i2cb_start_transaction (SHT20_ADDRESS, I2C_WRITE);
  i2cb_send_data (TRIGGER_HUMD_MEASURE_NOHOLD);
  delay_ms (100);
  i2cb_start_transaction (SHT20_ADDRESS, I2C_READ);

  h = i2cb_read (0);
  l = i2cb_read (0);
  c = i2cb_read (1);

  i2cb_stop();

  t = h;
  t <<= 8;
  t |= l & 0xfc;

  f = t;
  f /= 65536.;
  f *= 125.;
  f -= 6.;

  if (f < 0)
    f = 0;

  if (f > 100)
    f = 100;

  f *= 100.;

  t = (u32) (f + .5);
  tf = t % 100;
  t = t / 100;

  sprintf (ret, "%ld.%02ld", t, tf);


  return ret;

}