Dryer/src/sensor.c

#include "sensor.h"
#include "i2c.h"

/* Type def */
typedef union {
  uint32_t  u32;
  struct {
    #ifdef LITTLE_ENDIAN  // Byte-order is little endian
    uint8_t u8ll;
    uint8_t u8lh;
    uint8_t u8hl;
    uint8_t u8hh;
    #else                 // Byte-order is big endian
    uint8_t u8hh;
    uint8_t u8hl;
    uint8_t u8lh;
    uint8_t u8ll;
    #endif
  } s8;
} nt32_t;

/* Defines */
#define I2C_ADDR    0x70

#define CMD_INIT    0xe1
#define CMD_MEASURE 0xac
#define CMD_SRESET  0xba

#define STATUS_BUSY 0x80
#define STATUS_CMD  0x40
#define STATUS_CYC  0x20
#define STATUS_CAL  0x04

aht10_st_t AHT10_Init(void)
{
  i2c_status_t res;

  I2C_Start();

  res = I2C_WriteByte(I2C_ADDR);
  if (res != I2C_Ret_OK) {
    return AHT10_St_Err;
  }

  res = I2C_WriteByte(CMD_INIT);
  if (res != I2C_Ret_OK) {
    return AHT10_St_Err;
  }

  I2C_Stop();

  return AHT10_St_OK;
}

aht10_st_t AHT10_StartMeasure(void)
{
  i2c_status_t res;

  I2C_Start();

  res = I2C_WriteByte(I2C_ADDR);
  if (res != I2C_Ret_OK) {
    return AHT10_St_Err;
  }

  res = I2C_WriteByte(CMD_MEASURE);
  if (res != I2C_Ret_OK) {
    return AHT10_St_Err;
  }

  I2C_Stop();

  return AHT10_St_OK;
}

aht10_st_t AHT10_GetData(aht10_t * data)
{
  i2c_status_t res;

  I2C_Start();

  /* Send I2C read addr */
  res = I2C_WriteByte(I2C_ADDR | 0x1);
  if (res != I2C_Ret_OK) {
    return AHT10_St_Err;
  }

  /* Now read the value with NACK */
  uint8_t buf[6];
  res = I2C_ReadByte(buf, 0);
  if (res != I2C_Ret_OK) {
    return AHT10_St_Err;
  }

  I2C_Stop();

  if ((buf[0] & STATUS_BUSY) != 0) {
    return AHT10_St_Bsy;
  }
  /* Calculate values */
  uint32_t result;
  nt32_t tmp;

  /* Humidity = Srh * 100% / 2^20 */
  tmp.s8.u8hl = buf[1];
  tmp.s8.u8lh = buf[2];
  tmp.s8.u8ll = buf[3];
  result = tmp.u32 >> 4;
  result *= 100;
  result /= 1048576;
  data->Humidity = (int8_t)result;

  /* Temperature = St * 200 / 2^20 - 50 */
  tmp.s8.u8hl = buf[3] & 0xf;
  tmp.s8.u8lh = buf[4];
  tmp.s8.u8ll = buf[5];
  result = tmp.u32 * 200;
  result /= 1048576;
  data->Temperature = (int8_t)(result - 50);

  return AHT10_St_OK;
}