dht.cpp

Go to the documentation of this file.

#include "dht.h"
#include "esphome/core/helpers.h"
#include "esphome/core/log.h"
 
namespace esphome::dht {
 
static const char *const TAG = "dht";
 
void DHT::setup() {
  this->t_pin_->digital_write(true);
  this->t_pin_->setup();
#ifdef USE_ESP32
  this->t_pin_->pin_mode(this->t_pin_->get_flags() | gpio::FLAG_OUTPUT | gpio::FLAG_OPEN_DRAIN);
#endif
  this->t_pin_->digital_write(true);
}
 
void DHT::dump_config() {
  ESP_LOGCONFIG(TAG,
                "DHT:\n"
                "  %sModel: %s\n"
                "  Internal pull-up: %s",
                this->is_auto_detect_ ? LOG_STR_LITERAL("Auto-detected ") : "",
                this->model_ == DHT_MODEL_DHT11 ? LOG_STR_LITERAL("DHT11") : LOG_STR_LITERAL("DHT22 or equivalent"),
                ONOFF(this->t_pin_->get_flags() & gpio::FLAG_PULLUP));
  LOG_PIN("  Pin: ", this->t_pin_);
  LOG_UPDATE_INTERVAL(this);
  LOG_SENSOR("  ", "Temperature", this->temperature_sensor_);
  LOG_SENSOR("  ", "Humidity", this->humidity_sensor_);
}
 
void DHT::update() {
  float temperature, humidity;
  bool success;
  if (this->model_ == DHT_MODEL_AUTO_DETECT) {
    this->model_ = DHT_MODEL_DHT22;
    success = this->read_sensor_(&temperature, &humidity, false);
    if (!success) {
      this->model_ = DHT_MODEL_DHT11;
      return;
    }
  } else {
    success = this->read_sensor_(&temperature, &humidity, true);
  }
 
  if (success) {
    if (this->temperature_sensor_ != nullptr)
      this->temperature_sensor_->publish_state(temperature);
    if (this->humidity_sensor_ != nullptr)
      this->humidity_sensor_->publish_state(humidity);
    this->status_clear_warning();
  } else {
    ESP_LOGW(TAG, "Invalid readings");
    if (this->temperature_sensor_ != nullptr)
      this->temperature_sensor_->publish_state(NAN);
    if (this->humidity_sensor_ != nullptr)
      this->humidity_sensor_->publish_state(NAN);
    this->status_set_warning();
  }
}
 
void DHT::set_dht_model(DHTModel model) {
  this->model_ = model;
  this->is_auto_detect_ = model == DHT_MODEL_AUTO_DETECT;
}
 
bool HOT IRAM_ATTR DHT::read_sensor_(float *temperature, float *humidity, bool report_errors) {
  *humidity = NAN;
  *temperature = NAN;
 
  int error_code = 0;
  uint8_t data[5] = {};
 
#ifndef USE_ESP32
  this->pin_.pin_mode(gpio::FLAG_OUTPUT);
#endif
  this->pin_.digital_write(false);
 
  if (this->model_ == DHT_MODEL_DHT11) {
    delayMicroseconds(18000);
  } else if (this->model_ == DHT_MODEL_SI7021) {
    delayMicroseconds(500);
  } else if (this->model_ == DHT_MODEL_DHT22_TYPE2) {
    delayMicroseconds(2000);
  } else {
    delayMicroseconds(1000);
  }
 
#ifdef USE_ESP32
  this->pin_.digital_write(true);
#else
  this->pin_.pin_mode(this->t_pin_->get_flags());
#endif
 
  {
    InterruptLock lock;
    // Host pull up 20-40us then DHT response 80us
    // Start waiting for initial rising edge at the center when we
    // expect the DHT response (30us+40us)
    delayMicroseconds(70);
 
    uint8_t bit = 7;
    uint8_t byte = 0;
 
    // On 32-bit Xtensa/RISC-V cores, int8_t would require masking/sign-extension for comparisons
    // vs. native int. Using int i is native word size — small win in the timing-critical section.
    for (int i = -1; i < 40; i++) {
      uint32_t start_time = micros();
 
      // Wait for rising edge
      while (!this->pin_.digital_read()) {
        if (micros() - start_time > 90) {
          if (i < 0) {
            error_code = 1;  // line didn't clear
          } else {
            error_code = 2;  // rising edge for bit i timeout
          }
          break;
        }
      }
      if (error_code != 0)
        break;
 
      start_time = micros();
      uint32_t end_time = start_time;
 
      // Wait for falling edge
      while (this->pin_.digital_read()) {
        end_time = micros();
        if (end_time - start_time > 90) {
          if (i < 0) {
            error_code = 3;  // requesting data failed
          } else {
            error_code = 4;  // falling edge for bit i timeout
          }
          break;
        }
      }
      if (error_code != 0)
        break;
 
      if (i < 0)
        continue;
 
      if (end_time - start_time >= 40) {
        data[byte] |= 1 << bit;
      }
      if (bit == 0) {
        bit = 7;
        byte++;
      } else {
        bit--;
      }
    }
  }
  if (error_code != 0) {
    if (report_errors) {
      ESP_LOGW(TAG, ESP_LOG_MSG_COMM_FAIL);
    }
    return false;
  }
 
  ESP_LOGVV(TAG,
            "Data: Hum=0b" BYTE_TO_BINARY_PATTERN BYTE_TO_BINARY_PATTERN
            ", Temp=0b" BYTE_TO_BINARY_PATTERN BYTE_TO_BINARY_PATTERN ", Checksum=0b" BYTE_TO_BINARY_PATTERN,
            BYTE_TO_BINARY(data[0]), BYTE_TO_BINARY(data[1]), BYTE_TO_BINARY(data[2]), BYTE_TO_BINARY(data[3]),
            BYTE_TO_BINARY(data[4]));
 
  uint8_t checksum_a = data[0] + data[1] + data[2] + data[3];
  // On the DHT11, two algorithms for the checksum seem to be used, either the one from the DHT22,
  // or just using bytes 0 and 2
  uint8_t checksum_b = this->model_ == DHT_MODEL_DHT11 ? (data[0] + data[2]) : checksum_a;
 
  if (checksum_a != data[4] && checksum_b != data[4]) {
    if (report_errors) {
      ESP_LOGW(TAG, "Invalid checksum");
    }
    return false;
  }
 
  if (this->model_ == DHT_MODEL_DHT11) {
    if (checksum_a == data[4]) {
      // Data format: 8bit integral RH data + 8bit decimal RH data + 8bit integral T data + 8bit decimal T data + 8bit
      // check sum - some models always have 0 in the decimal part
      const uint16_t raw_temperature = static_cast<uint16_t>(data[2]) * 10 + (data[3] & 0x7F);
      *temperature = static_cast<float>(raw_temperature) / 10.0f;
      if ((data[3] & 0x80) != 0) {
        // negative
        *temperature *= -1;
      }
 
      const uint16_t raw_humidity = static_cast<uint16_t>(data[0]) * 10 + data[1];
      *humidity = static_cast<float>(raw_humidity) / 10.0f;
    } else {
      // For compatibility with DHT11 models which might only use 2 bytes checksums, only use the data from these two
      // bytes
      *temperature = data[2];
      *humidity = data[0];
    }
  } else {
    uint16_t raw_humidity = encode_uint16(data[0], data[1]);
    uint16_t raw_temperature = encode_uint16(data[2], data[3]);
 
    if (raw_temperature & 0x8000) {
      if (!(raw_temperature & 0x4000))
        raw_temperature = ~(raw_temperature & 0x7FFF);
    } else if (raw_temperature & 0x800) {
      raw_temperature |= 0xf000;
    }
 
    if (raw_temperature == 1 && raw_humidity == 10) {
      if (report_errors) {
        ESP_LOGW(TAG, "Invalid data");
      }
      return false;
    }
 
    *humidity = static_cast<float>(raw_humidity) * 0.1f;
    if (*humidity > 100.0f)
      *humidity = NAN;
    *temperature = static_cast<int16_t>(raw_temperature) * 0.1f;
  }
 
  if (*temperature == 0.0f && (*humidity == 1.0f || *humidity == 2.0f)) {
    if (report_errors) {
      ESP_LOGW(TAG, "Invalid data");
    }
    return false;
  }
  return true;
}
 
}  // namespace esphome::dht