aht10.cpp

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// Implementation based on:
//  - AHT10: https://github.com/Thinary/AHT10
//  - Official Datasheet (cn):
//  http://www.aosong.com/userfiles/files/media/aht10%E8%A7%84%E6%A0%BC%E4%B9%A6v1_1%EF%BC%8820191015%EF%BC%89.pdf
//  - Unofficial Translated Datasheet (en):
//  https://wiki.liutyi.info/download/attachments/30507639/Aosong_AHT10_en_draft_0c.pdf
//
// When configured for humidity, the log 'Components should block for at most 20-30ms in loop().' will be generated in
// verbose mode. This is due to technical specs of the sensor and can not be avoided.
//
// According to the datasheet, the component is supposed to respond in more than 75ms. In fact, it can answer almost
// immediately for temperature. But for humidity, it takes >90ms to get a valid data. From experience, we have best
// results making successive requests; the current implementation makes 3 attempts with a delay of 30ms each time.
 
#include "aht10.h"
#include "esphome/core/hal.h"
#include "esphome/core/helpers.h"
#include "esphome/core/log.h"
 
namespace esphome::aht10 {
 
static const char *const TAG = "aht10";
static const uint8_t AHT10_INITIALIZE_CMD[] = {0xE1, 0x08, 0x00};
static const uint8_t AHT20_INITIALIZE_CMD[] = {0xBE, 0x08, 0x00};
static const uint8_t AHT10_MEASURE_CMD[] = {0xAC, 0x33, 0x00};
static const uint8_t AHT10_SOFTRESET_CMD[] = {0xBA};
 
static const uint8_t AHT10_DEFAULT_DELAY = 5;     // ms, for initialization and temperature measurement
static const uint8_t AHT10_READ_DELAY = 80;       // ms, time to wait for conversion result
static const uint8_t AHT10_SOFTRESET_DELAY = 30;  // ms
 
static const uint8_t AHT10_ATTEMPTS = 3;  // safety margin, normally 3 attempts are enough: 3*30=90ms
static const uint8_t AHT10_INIT_ATTEMPTS = 10;
 
static const uint8_t AHT10_STATUS_BUSY = 0x80;
 
static const float AHT10_DIVISOR = 1048576.0f;  // 2^20, used for temperature and humidity calculations
 
void AHT10Component::setup() {
  if (this->write(AHT10_SOFTRESET_CMD, sizeof(AHT10_SOFTRESET_CMD)) != i2c::ERROR_OK) {
    ESP_LOGE(TAG, "Reset failed");
  }
  delay(AHT10_SOFTRESET_DELAY);
 
  i2c::ErrorCode error_code = i2c::ERROR_INVALID_ARGUMENT;
  switch (this->variant_) {
    case AHT10Variant::AHT20:
      error_code = this->write(AHT20_INITIALIZE_CMD, sizeof(AHT20_INITIALIZE_CMD));
      break;
    case AHT10Variant::AHT10:
      error_code = this->write(AHT10_INITIALIZE_CMD, sizeof(AHT10_INITIALIZE_CMD));
      break;
  }
  if (error_code != i2c::ERROR_OK) {
    ESP_LOGE(TAG, ESP_LOG_MSG_COMM_FAIL);
    this->mark_failed();
    return;
  }
  uint8_t cal_attempts = 0;
  uint8_t data = AHT10_STATUS_BUSY;
  while (data & AHT10_STATUS_BUSY) {
    delay(AHT10_DEFAULT_DELAY);
    if (this->read(&data, 1) != i2c::ERROR_OK) {
      ESP_LOGE(TAG, ESP_LOG_MSG_COMM_FAIL);
      this->mark_failed();
      return;
    }
    ++cal_attempts;
    if (cal_attempts > AHT10_INIT_ATTEMPTS) {
      ESP_LOGE(TAG, "Initialization timed out");
      this->mark_failed();
      return;
    }
  }
  if ((data & 0x68) != 0x08) {  // Bit[6:5] = 0b00, NORMAL mode and Bit[3] = 0b1, CALIBRATED
    ESP_LOGE(TAG, "Initialization failed");
    this->mark_failed();
    return;
  }
}
 
void AHT10Component::restart_read_() {
  if (this->read_count_ == AHT10_ATTEMPTS) {
    this->read_count_ = 0;
    this->status_set_error(LOG_STR("Reading timed out"));
    return;
  }
  this->read_count_++;
  this->set_timeout(AHT10_READ_DELAY, [this]() { this->read_data_(); });
}
 
void AHT10Component::read_data_() {
  uint8_t data[6];
  if (this->read_count_ > 1) {
    ESP_LOGD(TAG, "Read attempt %d at %ums", this->read_count_, (unsigned) (millis() - this->start_time_));
  }
  if (this->read(data, 6) != i2c::ERROR_OK) {
    this->status_set_warning(LOG_STR("Read failed, will retry"));
    this->restart_read_();
    return;
  }
 
  if ((data[0] & 0x80) == 0x80) {  // Bit[7] = 0b1, device is busy
    ESP_LOGD(TAG, "Device busy, will retry");
    this->restart_read_();
    return;
  }
  if (data[1] == 0x0 && data[2] == 0x0 && (data[3] >> 4) == 0x0) {
    // Invalid humidity (0x0)
    if (this->humidity_sensor_ == nullptr) {
      ESP_LOGV(TAG, "Invalid humidity (reading not required)");
    } else {
      ESP_LOGD(TAG, "Invalid humidity, retrying");
      if (this->write(AHT10_MEASURE_CMD, sizeof(AHT10_MEASURE_CMD)) != i2c::ERROR_OK) {
        this->status_set_warning(LOG_STR(ESP_LOG_MSG_COMM_FAIL));
      }
      this->restart_read_();
      return;
    }
  }
  if (this->read_count_ > 1) {
    ESP_LOGD(TAG, "Success at %ums", (unsigned) (millis() - this->start_time_));
  }
  uint32_t raw_temperature = encode_uint24(data[3] & 0xF, data[4], data[5]);
  uint32_t raw_humidity = encode_uint24(data[1], data[2], data[3]) >> 4;
 
  if (this->temperature_sensor_ != nullptr) {
    float temperature = ((200.0f * static_cast<float>(raw_temperature)) / AHT10_DIVISOR) - 50.0f;
    this->temperature_sensor_->publish_state(temperature);
  }
  if (this->humidity_sensor_ != nullptr) {
    float humidity = raw_humidity == 0 ? NAN : static_cast<float>(raw_humidity) * 100.0f / AHT10_DIVISOR;
    if (std::isnan(humidity)) {
      ESP_LOGW(TAG, "Invalid humidity reading (0%%), ");
    }
    this->humidity_sensor_->publish_state(humidity);
  }
  this->status_clear_warning();
  this->read_count_ = 0;
}
void AHT10Component::update() {
  if (this->read_count_ != 0)
    return;
  this->start_time_ = millis();
  if (this->write(AHT10_MEASURE_CMD, sizeof(AHT10_MEASURE_CMD)) != i2c::ERROR_OK) {
    this->status_set_warning(LOG_STR(ESP_LOG_MSG_COMM_FAIL));
    return;
  }
  this->restart_read_();
}
 
void AHT10Component::dump_config() {
  ESP_LOGCONFIG(TAG, "AHT10:");
  LOG_I2C_DEVICE(this);
  if (this->is_failed()) {
    ESP_LOGE(TAG, ESP_LOG_MSG_COMM_FAIL);
  }
  LOG_SENSOR("  ", "Temperature", this->temperature_sensor_);
  LOG_SENSOR("  ", "Humidity", this->humidity_sensor_);
}
 
}  // namespace esphome::aht10