bme680.cpp

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#include "bme680.h"
#include "esphome/core/hal.h"
#include "esphome/core/helpers.h"
#include "esphome/core/log.h"
 
namespace esphome::bme680 {
 
ESPHOME_LOG_TAG(TAG, "bme680.sensor");
 
static constexpr uint32_t DATA_TIMEOUT_ID = 0;
 
static const uint8_t BME680_REGISTER_COEFF1 = 0x89;
static const uint8_t BME680_REGISTER_COEFF2 = 0xE1;
 
static const uint8_t BME680_REGISTER_CONFIG = 0x75;
static const uint8_t BME680_REGISTER_CONTROL_MEAS = 0x74;
static const uint8_t BME680_REGISTER_CONTROL_HUMIDITY = 0x72;
static const uint8_t BME680_REGISTER_CONTROL_GAS1 = 0x71;
static const uint8_t BME680_REGISTER_CONTROL_GAS0 = 0x70;
static const uint8_t BME680_REGISTER_HEATER_HEAT0 = 0x5A;
static const uint8_t BME680_REGISTER_HEATER_WAIT0 = 0x64;
 
static const uint8_t BME680_REGISTER_CHIPID = 0xD0;
 
static const uint8_t BME680_REGISTER_FIELD0 = 0x1D;
 
constexpr float BME680_GAS_LOOKUP_TABLE_1[16] PROGMEM = {0.0, 0.0, 0.0,  0.0,  0.0, -1.0, 0.0, -0.8,
                                                         0.0, 0.0, -0.2, -0.5, 0.0, -1.0, 0.0, 0.0};
 
constexpr float BME680_GAS_LOOKUP_TABLE_2[16] PROGMEM = {0.0,  0.0, 0.0, 0.0, 0.1, 0.7, 0.0, -0.8,
                                                         -0.1, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0};
 
[[maybe_unused]] static const char *oversampling_to_str(BME680Oversampling oversampling) {
  switch (oversampling) {
    case BME680_OVERSAMPLING_NONE:
      return "None";
    case BME680_OVERSAMPLING_1X:
      return "1x";
    case BME680_OVERSAMPLING_2X:
      return "2x";
    case BME680_OVERSAMPLING_4X:
      return "4x";
    case BME680_OVERSAMPLING_8X:
      return "8x";
    case BME680_OVERSAMPLING_16X:
      return "16x";
    default:
      return "UNKNOWN";
  }
}
 
[[maybe_unused]] static const char *iir_filter_to_str(BME680IIRFilter filter) {
  switch (filter) {
    case BME680_IIR_FILTER_OFF:
      return "OFF";
    case BME680_IIR_FILTER_1X:
      return "1x";
    case BME680_IIR_FILTER_3X:
      return "3x";
    case BME680_IIR_FILTER_7X:
      return "7x";
    case BME680_IIR_FILTER_15X:
      return "15x";
    case BME680_IIR_FILTER_31X:
      return "31x";
    case BME680_IIR_FILTER_63X:
      return "63x";
    case BME680_IIR_FILTER_127X:
      return "127x";
    default:
      return "UNKNOWN";
  }
}
 
void BME680Component::setup() {
  if (!this->setup_registers_())
    this->mark_failed(LOG_STR(ESP_LOG_MSG_COMM_FAIL));
}
 
bool BME680Component::setup_registers_() {
  uint8_t chip_id;
  if (!this->read_byte(BME680_REGISTER_CHIPID, &chip_id) || chip_id != 0x61) {
    return false;
  }
 
  // Read calibration
  uint8_t coeff1[25];
  if (!this->read_bytes(BME680_REGISTER_COEFF1, coeff1, 25)) {
    return false;
  }
  uint8_t coeff2[16];
  if (!this->read_bytes(BME680_REGISTER_COEFF2, coeff2, 16)) {
    return false;
  }
 
  this->calibration_.t1 = encode_value_le<uint16_t>(&coeff2[8]);
  this->calibration_.t2 = encode_value_le<int16_t>(&coeff1[1]);
  this->calibration_.t3 = coeff1[3];
 
  this->calibration_.h1 = coeff2[2] << 4 | (coeff2[1] & 0x0F);
  this->calibration_.h2 = coeff2[0] << 4 | coeff2[1] >> 4;
  this->calibration_.h3 = coeff2[3];
  this->calibration_.h4 = coeff2[4];
  this->calibration_.h5 = coeff2[5];
  this->calibration_.h6 = coeff2[6];
  this->calibration_.h7 = coeff2[7];
 
  this->calibration_.p1 = encode_value_le<uint16_t>(&coeff1[5]);
  this->calibration_.p2 = encode_value_le<int16_t>(&coeff1[7]);
  this->calibration_.p3 = coeff1[9];
  this->calibration_.p4 = encode_value_le<int16_t>(&coeff1[11]);
  this->calibration_.p5 = encode_value_le<int16_t>(&coeff1[13]);
  this->calibration_.p6 = coeff1[16];
  this->calibration_.p7 = coeff1[15];
  this->calibration_.p8 = encode_value_le<int16_t>(&coeff1[19]);
  this->calibration_.p9 = encode_value_le<int16_t>(&coeff1[21]);
  this->calibration_.p10 = coeff1[23];
 
  this->calibration_.gh1 = coeff2[14];
  this->calibration_.gh2 = encode_value<int16_t>(&coeff2[12]);
  this->calibration_.gh3 = coeff2[15];
 
  uint8_t temp_var = 0;
  if (!this->read_byte(0x02, &temp_var)) {
    return false;
  }
  this->calibration_.res_heat_range = ((temp_var & 0x30) / 16);
 
  if (!this->read_byte(0x00, &temp_var)) {
    return false;
  }
  this->calibration_.res_heat_val = (int8_t) temp_var;
 
  if (!this->read_byte(0x04, &temp_var)) {
    return false;
  }
  this->calibration_.range_sw_err = ((int8_t) temp_var & (int8_t) 0xf0) / 16;
 
  this->calibration_.ambient_temperature = 25;  // prime ambient temperature
 
  // Config register
  uint8_t config_register;
  if (!this->read_byte(BME680_REGISTER_CONFIG, &config_register)) {
    return false;
  }
  config_register &= ~0b00011100;
  config_register |= (this->iir_filter_ & 0b111) << 2;
  if (!this->write_byte(BME680_REGISTER_CONFIG, config_register)) {
    return false;
  }
 
  // Humidity control register
  uint8_t hum_control;
  if (!this->read_byte(BME680_REGISTER_CONTROL_HUMIDITY, &hum_control)) {
    return false;
  }
  hum_control &= ~0b00000111;
  hum_control |= this->humidity_oversampling_ & 0b111;
  if (!this->write_byte(BME680_REGISTER_CONTROL_HUMIDITY, hum_control)) {
    return false;
  }
 
  // Gas 1 control register
  uint8_t gas1_control;
  if (!this->read_byte(BME680_REGISTER_CONTROL_GAS1, &gas1_control)) {
    return false;
  }
  gas1_control &= ~0b00011111;
  gas1_control |= 1 << 4;
  gas1_control |= 0;  // profile 0
  if (!this->write_byte(BME680_REGISTER_CONTROL_GAS1, gas1_control)) {
    return false;
  }
 
  const bool heat_off = this->heater_temperature_ == 0 || this->heater_duration_ == 0;
 
  // Gas 0 control register
  uint8_t gas0_control;
  if (!this->read_byte(BME680_REGISTER_CONTROL_GAS0, &gas0_control)) {
    return false;
  }
  gas0_control &= ~0b00001000;
  gas0_control |= heat_off << 3;
  if (!this->write_byte(BME680_REGISTER_CONTROL_GAS0, gas0_control)) {
    return false;
  }
 
  if (!heat_off) {
    // Gas Heater Temperature
    uint8_t temperature = this->calc_heater_resistance_(this->heater_temperature_);
    if (!this->write_byte(BME680_REGISTER_HEATER_HEAT0, temperature)) {
      return false;
    }
 
    // Gas Heater Duration
    uint8_t duration = this->calc_heater_duration_(this->heater_duration_);
 
    if (!this->write_byte(BME680_REGISTER_HEATER_WAIT0, duration)) {
      return false;
    }
  }
  return true;
}
 
void BME680Component::dump_config() {
  ESP_LOGCONFIG(TAG, "BME680:");
  LOG_I2C_DEVICE(this);
  ESP_LOGCONFIG(TAG, "  IIR Filter: %s", iir_filter_to_str(this->iir_filter_));
  LOG_UPDATE_INTERVAL(this);
 
  LOG_SENSOR("  ", "Temperature", this->temperature_sensor_);
  ESP_LOGCONFIG(TAG, "    Oversampling: %s", oversampling_to_str(this->temperature_oversampling_));
  LOG_SENSOR("  ", "Pressure", this->pressure_sensor_);
  ESP_LOGCONFIG(TAG, "    Oversampling: %s", oversampling_to_str(this->pressure_oversampling_));
  LOG_SENSOR("  ", "Humidity", this->humidity_sensor_);
  ESP_LOGCONFIG(TAG, "    Oversampling: %s", oversampling_to_str(this->humidity_oversampling_));
  LOG_SENSOR("  ", "Gas Resistance", this->gas_resistance_sensor_);
  if (this->heater_duration_ == 0 || this->heater_temperature_ == 0) {
    ESP_LOGCONFIG(TAG, "  Heater OFF");
  } else {
    ESP_LOGCONFIG(TAG, "  Heater temperature=%u°C duration=%ums", this->heater_temperature_, this->heater_duration_);
  }
}
 
void BME680Component::update() {
  uint8_t meas_control = 0;  // No need to fetch, we're setting all fields
  meas_control |= (this->temperature_oversampling_ & 0b111) << 5;
  meas_control |= (this->pressure_oversampling_ & 0b111) << 2;
  meas_control |= 0b01;  // forced mode
  if (!this->write_byte(BME680_REGISTER_CONTROL_MEAS, meas_control)) {
    this->status_set_warning();
    return;
  }
 
  this->set_timeout(DATA_TIMEOUT_ID, this->calc_meas_duration_(), [this]() { this->read_data_(); });
}
 
uint8_t BME680Component::calc_heater_resistance_(uint16_t temperature) {
  if (temperature < 200)
    temperature = 200;
  if (temperature > 400)
    temperature = 400;
 
  const int8_t ambient_temperature = this->calibration_.ambient_temperature;
  const int8_t gh1 = this->calibration_.gh1;
  const int16_t gh2 = this->calibration_.gh2;
  const int8_t gh3 = this->calibration_.gh3;
  const uint8_t res_heat_range = this->calibration_.res_heat_range;
  const int8_t res_heat_val = this->calibration_.res_heat_val;
 
  uint8_t heatr_res;
  int32_t var1;
  int32_t var2;
  int32_t var3;
  int32_t var4;
  int32_t var5;
  int32_t heatr_res_x100;
 
  var1 = (((int32_t) ambient_temperature * gh3) / 1000) * 256;
  var2 = (gh1 + 784) * (((((gh2 + 154009) * temperature * 5) / 100) + 3276800) / 10);
  var3 = var1 + (var2 / 2);
  var4 = (var3 / (res_heat_range + 4));
  var5 = (131 * res_heat_val) + 65536;
  heatr_res_x100 = (int32_t) (((var4 / var5) - 250) * 34);
  heatr_res = (uint8_t) ((heatr_res_x100 + 50) / 100);
 
  return heatr_res;
}
uint8_t BME680Component::calc_heater_duration_(uint16_t duration) {
  uint8_t factor = 0;
  uint8_t duration_value;
 
  if (duration >= 0xfc0) {
    duration_value = 0xff;
  } else {
    while (duration > 0x3F) {
      duration /= 4;
      factor += 1;
    }
    duration_value = duration + (factor * 64);
  }
 
  return duration_value;
}
void BME680Component::read_data_() {
  uint8_t data[15];
  if (!this->status_comm_result(this->read_bytes(BME680_REGISTER_FIELD0, data, 15))) {
    if (this->temperature_sensor_ != nullptr)
      this->temperature_sensor_->publish_state(NAN);
    if (this->pressure_sensor_ != nullptr)
      this->pressure_sensor_->publish_state(NAN);
    if (this->humidity_sensor_ != nullptr)
      this->humidity_sensor_->publish_state(NAN);
    if (this->gas_resistance_sensor_ != nullptr)
      this->gas_resistance_sensor_->publish_state(NAN);
    ESP_LOGW(TAG, ESP_LOG_MSG_COMM_FAIL);
    return;
  }
 
  uint32_t raw_temperature = (uint32_t(data[5]) << 12) | (uint32_t(data[6]) << 4) | (uint32_t(data[7]) >> 4);
  uint32_t raw_pressure = (uint32_t(data[2]) << 12) | (uint32_t(data[3]) << 4) | (uint32_t(data[4]) >> 4);
  uint32_t raw_humidity = (uint32_t(data[8]) << 8) | uint32_t(data[9]);
  uint16_t raw_gas = (uint16_t) ((uint32_t) data[13] * 4 | (((uint32_t) data[14]) / 64));
  uint8_t gas_range = data[14] & 0x0F;
 
  float temperature = this->calc_temperature_(raw_temperature);
  float pressure = this->calc_pressure_(raw_pressure);
  float humidity = this->calc_humidity_(raw_humidity);
  float gas_resistance = this->calc_gas_resistance_(raw_gas, gas_range);
 
  bool gas_valid = (data[14] >> 5) & 1;
  bool heat_stable = (data[14] >> 4) & 1;
  if (this->heater_temperature_ == 0 || this->heater_duration_ == 0)
    heat_stable = true;  // Allow reporting gas resistance when heater is disabled
 
  ESP_LOGD(TAG, "Got temperature=%.1f°C pressure=%.1fhPa humidity=%.1f%% gas_resistance=%.1fΩ", temperature, pressure,
           humidity, gas_resistance);
  if (!gas_valid) {
    ESP_LOGW(TAG, "Gas measurement unsuccessful, reading invalid!");
  }
  if (!heat_stable) {
    ESP_LOGW(TAG, "Heater unstable, reading invalid! (Normal for a few readings after a power cycle)");
  }
 
  if (this->temperature_sensor_ != nullptr)
    this->temperature_sensor_->publish_state(temperature);
  if (this->pressure_sensor_ != nullptr)
    this->pressure_sensor_->publish_state(pressure);
  if (this->humidity_sensor_ != nullptr)
    this->humidity_sensor_->publish_state(humidity);
  if (this->gas_resistance_sensor_ != nullptr) {
    if (gas_valid && heat_stable) {
      this->gas_resistance_sensor_->publish_state(gas_resistance);
    } else {
      this->status_set_warning();
      this->gas_resistance_sensor_->publish_state(NAN);
    }
  }
}
 
float BME680Component::calc_temperature_(uint32_t raw_temperature) {
  float var1 = 0;
  float var2 = 0;
  float var3 = 0;
  float calc_temp = 0;
  float temp_adc = raw_temperature;
 
  const float t1 = this->calibration_.t1;
  const float t2 = this->calibration_.t2;
  const float t3 = this->calibration_.t3;
 
  /* calculate var1 data */
  var1 = ((temp_adc / 16384.0f) - (t1 / 1024.0f)) * t2;
 
  /* calculate var2 data */
  var3 = (temp_adc / 131072.0f) - (t1 / 8192.0f);
  var2 = var3 * var3 * t3 * 16.0f;
 
  /* t_fine value*/
  this->calibration_.tfine = (var1 + var2);
 
  /* compensated temperature data*/
  calc_temp = ((this->calibration_.tfine) / 5120.0f);
 
  return calc_temp;
}
float BME680Component::calc_pressure_(uint32_t raw_pressure) {
  const float tfine = this->calibration_.tfine;
  const float p1 = this->calibration_.p1;
  const float p2 = this->calibration_.p2;
  const float p3 = this->calibration_.p3;
  const float p4 = this->calibration_.p4;
  const float p5 = this->calibration_.p5;
  const float p6 = this->calibration_.p6;
  const float p7 = this->calibration_.p7;
  const float p8 = this->calibration_.p8;
  const float p9 = this->calibration_.p9;
  const float p10 = this->calibration_.p10;
 
  float var1 = 0;
  float var2 = 0;
  float var3 = 0;
  float var4 = 0;
  float calc_pres = 0;
 
  var1 = (tfine / 2.0f) - 64000.0f;
  var2 = var1 * var1 * (p6 / 131072.0f);
  var2 = var2 + var1 * p5 * 2.0f;
  var2 = (var2 / 4.0f) + (p4 * 65536.0f);
  var1 = (((p3 * var1 * var1) / 16384.0f) + (p2 * var1)) / 524288.0f;
  var1 = (1.0f + (var1 / 32768.0f)) * p1;
  calc_pres = 1048576.0f - float(raw_pressure);
 
  /* Avoid exception caused by division by zero */
  if (int(var1) != 0) {
    calc_pres = ((calc_pres - (var2 / 4096.0f)) * 6250.0f) / var1;
    var1 = (p9 * calc_pres * calc_pres) / 2147483648.0f;
    var2 = calc_pres * (p8 / 32768.0f);
    var4 = calc_pres / 256.0f;
    var3 = var4 * var4 * var4 * (p10 / 131072.0f);
    calc_pres = calc_pres + (var1 + var2 + var3 + (p7 * 128.0f)) / 16.0f;
  } else {
    calc_pres = 0;
  }
 
  return calc_pres / 100.0f;
}
 
float BME680Component::calc_humidity_(uint16_t raw_humidity) {
  const float tfine = this->calibration_.tfine;
  const float h1 = this->calibration_.h1;
  const float h2 = this->calibration_.h2;
  const float h3 = this->calibration_.h3;
  const float h4 = this->calibration_.h4;
  const float h5 = this->calibration_.h5;
  const float h6 = this->calibration_.h6;
  const float h7 = this->calibration_.h7;
 
  float calc_hum = 0;
  float var1 = 0;
  float var2 = 0;
  float var3 = 0;
  float var4 = 0;
  float temp_comp;
 
  /* compensated temperature data*/
  temp_comp = tfine / 5120.0f;
 
  var1 = float(raw_humidity) - (h1 * 16.0f + ((h3 / 2.0f) * temp_comp));
  var2 = var1 *
         (((h2 / 262144.0f) * (1.0f + ((h4 / 16384.0f) * temp_comp) + ((h5 / 1048576.0f) * temp_comp * temp_comp))));
  var3 = h6 / 16384.0f;
  var4 = h7 / 2097152.0f;
 
  calc_hum = var2 + (var3 + var4 * temp_comp) * var2 * var2;
 
  if (calc_hum > 100.0f) {
    calc_hum = 100.0f;
  } else if (calc_hum < 0.0f) {
    calc_hum = 0.0f;
  }
 
  return calc_hum;
}
float BME680Component::calc_gas_resistance_(uint16_t raw_gas, uint8_t range) {
  float calc_gas_res;
  float var1 = 0;
  float var2 = 0;
  float var3 = 0;
  float raw_gas_f = raw_gas;
  float range_f = 1U << range;
  const float range_sw_err = this->calibration_.range_sw_err;
 
  var1 = 1340.0f + (5.0f * range_sw_err);
  var2 = var1 * (1.0f + BME680_GAS_LOOKUP_TABLE_1[range] / 100.0f);
  var3 = 1.0f + (BME680_GAS_LOOKUP_TABLE_2[range] / 100.0f);
 
  calc_gas_res = 1.0f / (var3 * 0.000000125f * range_f * (((raw_gas_f - 512.0f) / var2) + 1.0f));
 
  return calc_gas_res;
}
uint32_t BME680Component::calc_meas_duration_() {
  uint32_t tph_dur;  // Calculate in us
  uint32_t meas_cycles;
  const uint8_t os_to_meas_cycles[6] = {0, 1, 2, 4, 8, 16};
 
  meas_cycles = os_to_meas_cycles[this->temperature_oversampling_];
  meas_cycles += os_to_meas_cycles[this->pressure_oversampling_];
  meas_cycles += os_to_meas_cycles[this->humidity_oversampling_];
 
  /* TPH measurement duration */
  tph_dur = meas_cycles * 1963u;
  tph_dur += 477 * 4;  // TPH switching duration
  tph_dur += 477 * 5;  // Gas measurement duration
  tph_dur += 500;      // Get it to the closest whole number.
  tph_dur /= 1000;     // Convert to ms
 
  tph_dur += 1;  // Wake up duration of 1ms
 
  /* The remaining time should be used for heating */
  tph_dur += this->heater_duration_;
 
  return tph_dur;
}
void BME680Component::set_temperature_oversampling(BME680Oversampling temperature_oversampling) {
  this->temperature_oversampling_ = temperature_oversampling;
}
void BME680Component::set_pressure_oversampling(BME680Oversampling pressure_oversampling) {
  this->pressure_oversampling_ = pressure_oversampling;
}
void BME680Component::set_humidity_oversampling(BME680Oversampling humidity_oversampling) {
  this->humidity_oversampling_ = humidity_oversampling;
}
void BME680Component::set_heater(uint16_t heater_temperature, uint16_t heater_duration) {
  this->heater_temperature_ = heater_temperature;
  this->heater_duration_ = heater_duration;
}
 
}  // namespace esphome::bme680