mhz19.cpp

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#include "mhz19.h"
#include "esphome/core/log.h"
 
#include <cinttypes>
 
namespace esphome::mhz19 {
 
static const char *const TAG = "mhz19";
static const uint8_t MHZ19_REQUEST_LENGTH = 8;
static const uint8_t MHZ19_RESPONSE_LENGTH = 9;
static const uint8_t MHZ19_COMMAND_GET_PPM[] = {0xFF, 0x01, 0x86, 0x00, 0x00, 0x00, 0x00, 0x00};
static const uint8_t MHZ19_COMMAND_ABC_ENABLE[] = {0xFF, 0x01, 0x79, 0xA0, 0x00, 0x00, 0x00, 0x00};
static const uint8_t MHZ19_COMMAND_ABC_DISABLE[] = {0xFF, 0x01, 0x79, 0x00, 0x00, 0x00, 0x00, 0x00};
static const uint8_t MHZ19_COMMAND_CALIBRATE_ZERO[] = {0xFF, 0x01, 0x87, 0x00, 0x00, 0x00, 0x00, 0x00};
static const uint8_t MHZ19_COMMAND_DETECTION_RANGE_0_2000PPM[] = {0xFF, 0x01, 0x99, 0x00, 0x00, 0x00, 0x07, 0xD0};
static const uint8_t MHZ19_COMMAND_DETECTION_RANGE_0_5000PPM[] = {0xFF, 0x01, 0x99, 0x00, 0x00, 0x00, 0x13, 0x88};
static const uint8_t MHZ19_COMMAND_DETECTION_RANGE_0_10000PPM[] = {0xFF, 0x01, 0x99, 0x00, 0x00, 0x00, 0x27, 0x10};
 
#if ESPHOME_LOG_LEVEL >= ESPHOME_LOG_LEVEL_DEBUG
static const LogString *detection_range_to_log_string(MHZ19DetectionRange range) {
  switch (range) {
    case MHZ19_DETECTION_RANGE_0_2000PPM:
      return LOG_STR("0-2000 ppm");
    case MHZ19_DETECTION_RANGE_0_5000PPM:
      return LOG_STR("0-5000 ppm");
    case MHZ19_DETECTION_RANGE_0_10000PPM:
      return LOG_STR("0-10000 ppm");
    default:
      return LOG_STR("default");
  }
}
#endif
 
uint8_t mhz19_checksum(const uint8_t *command) {
  uint8_t sum = 0;
  for (uint8_t i = 1; i < MHZ19_REQUEST_LENGTH; i++) {
    sum += command[i];
  }
  return 0xFF - sum + 0x01;
}
 
void MHZ19Component::setup() {
  if (this->abc_boot_logic_ == MHZ19_ABC_ENABLED) {
    this->abc_enable();
  } else if (this->abc_boot_logic_ == MHZ19_ABC_DISABLED) {
    this->abc_disable();
  }
 
  this->range_set(this->detection_range_);
}
 
void MHZ19Component::update() {
  uint32_t now_ms = millis();
  uint32_t warmup_ms = this->warmup_seconds_ * 1000;
  if (now_ms < warmup_ms) {
    ESP_LOGW(TAG, "MHZ19 warming up, %" PRIu32 " s left", (warmup_ms - now_ms) / 1000);
    this->status_set_warning();
    return;
  }
 
  uint8_t response[MHZ19_RESPONSE_LENGTH];
  if (!this->mhz19_write_command_(MHZ19_COMMAND_GET_PPM, response)) {
    ESP_LOGW(TAG, "Reading data from MHZ19 failed!");
    this->status_set_warning();
    return;
  }
 
  if (response[0] != 0xFF || response[1] != 0x86) {
    ESP_LOGW(TAG, "Invalid preamble from MHZ19!");
    this->status_set_warning();
    return;
  }
 
  uint8_t checksum = mhz19_checksum(response);
  if (response[8] != checksum) {
    ESP_LOGW(TAG, "MHZ19 Checksum doesn't match: 0x%02X!=0x%02X", response[8], checksum);
    this->status_set_warning();
    return;
  }
 
  this->status_clear_warning();
  const uint16_t ppm = (uint16_t(response[2]) << 8) | response[3];
  const int temp = int(response[4]) - 40;
  const uint8_t status = response[5];
 
  ESP_LOGD(TAG, "MHZ19 Received CO₂=%uppm Temperature=%d°C Status=0x%02X", ppm, temp, status);
  if (this->co2_sensor_ != nullptr)
    this->co2_sensor_->publish_state(ppm);
  if (this->temperature_sensor_ != nullptr)
    this->temperature_sensor_->publish_state(temp);
}
 
void MHZ19Component::calibrate_zero() {
  ESP_LOGD(TAG, "MHZ19 Calibrating zero point");
  this->mhz19_write_command_(MHZ19_COMMAND_CALIBRATE_ZERO, nullptr);
}
 
void MHZ19Component::abc_enable() {
  ESP_LOGD(TAG, "MHZ19 Enabling automatic baseline calibration");
  this->mhz19_write_command_(MHZ19_COMMAND_ABC_ENABLE, nullptr);
}
 
void MHZ19Component::abc_disable() {
  ESP_LOGD(TAG, "MHZ19 Disabling automatic baseline calibration");
  this->mhz19_write_command_(MHZ19_COMMAND_ABC_DISABLE, nullptr);
}
 
void MHZ19Component::range_set(MHZ19DetectionRange detection_range) {
  const uint8_t *command;
  switch (detection_range) {
    case MHZ19_DETECTION_RANGE_0_2000PPM:
      command = MHZ19_COMMAND_DETECTION_RANGE_0_2000PPM;
      break;
    case MHZ19_DETECTION_RANGE_0_5000PPM:
      command = MHZ19_COMMAND_DETECTION_RANGE_0_5000PPM;
      break;
    case MHZ19_DETECTION_RANGE_0_10000PPM:
      command = MHZ19_COMMAND_DETECTION_RANGE_0_10000PPM;
      break;
    default:
      ESP_LOGV(TAG, "Using previously set detection range (no change)");
      return;
  }
  ESP_LOGD(TAG, "Setting detection range to %s", LOG_STR_ARG(detection_range_to_log_string(detection_range)));
  this->mhz19_write_command_(command, nullptr);
}
 
bool MHZ19Component::mhz19_write_command_(const uint8_t *command, uint8_t *response) {
  // Empty RX Buffer
  while (this->available())
    this->read();
  this->write_array(command, MHZ19_REQUEST_LENGTH);
  this->write_byte(mhz19_checksum(command));
  this->flush();
 
  if (response == nullptr)
    return true;
 
  return this->read_array(response, MHZ19_RESPONSE_LENGTH);
}
 
void MHZ19Component::dump_config() {
  ESP_LOGCONFIG(TAG, "MH-Z19:");
  LOG_SENSOR("  ", "CO2", this->co2_sensor_);
  LOG_SENSOR("  ", "Temperature", this->temperature_sensor_);
  this->check_uart_settings(9600);
 
  if (this->abc_boot_logic_ == MHZ19_ABC_ENABLED) {
    ESP_LOGCONFIG(TAG, "  Automatic baseline calibration enabled on boot");
  } else if (this->abc_boot_logic_ == MHZ19_ABC_DISABLED) {
    ESP_LOGCONFIG(TAG, "  Automatic baseline calibration disabled on boot");
  }
 
  ESP_LOGCONFIG(TAG, "  Warmup time: %" PRIu32 " s", this->warmup_seconds_);
  ESP_LOGCONFIG(TAG, "  Detection range: %s", LOG_STR_ARG(detection_range_to_log_string(this->detection_range_)));
}
 
}  // namespace esphome::mhz19