wts01.cpp

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#include "wts01.h"
#include "esphome/core/log.h"
#include <cmath>
 
namespace esphome::wts01 {
 
constexpr uint8_t HEADER_1 = 0x55;
constexpr uint8_t HEADER_2 = 0x01;
constexpr uint8_t HEADER_3 = 0x01;
constexpr uint8_t HEADER_4 = 0x04;
 
ESPHOME_LOG_TAG(TAG, "wts01");
 
void WTS01Sensor::loop() {
  this->read_available([this](uint8_t c) { this->handle_char_(c); });
}
 
void WTS01Sensor::dump_config() { LOG_SENSOR("", "WTS01 Sensor", this); }
 
void WTS01Sensor::handle_char_(uint8_t c) {
  // State machine for processing the header. Reset if something doesn't match.
  if (this->buffer_pos_ == 0 && c != HEADER_1) {
    return;
  }
 
  if (this->buffer_pos_ == 1 && c != HEADER_2) {
    this->buffer_pos_ = 0;
    return;
  }
 
  if (this->buffer_pos_ == 2 && c != HEADER_3) {
    this->buffer_pos_ = 0;
    return;
  }
 
  if (this->buffer_pos_ == 3 && c != HEADER_4) {
    this->buffer_pos_ = 0;
    return;
  }
 
  // Add byte to buffer
  this->buffer_[this->buffer_pos_++] = c;
 
  // Process complete packet
  if (this->buffer_pos_ >= PACKET_SIZE) {
    this->process_packet_();
    this->buffer_pos_ = 0;
  }
}
 
void WTS01Sensor::process_packet_() {
  // Based on Tasmota implementation
  // Format: 55 01 01 04 01 11 16 12 95
  // header            T  Td Ck  - T = Temperature, Td = Temperature decimal, Ck = Checksum
  const uint8_t calculated_checksum = sum_bytes(this->buffer_, PACKET_SIZE - 1);
 
  uint8_t received_checksum = this->buffer_[PACKET_SIZE - 1];
  if (calculated_checksum != received_checksum) {
    ESP_LOGW(TAG, "WTS01 Checksum doesn't match: 0x%02X != 0x%02X", received_checksum, calculated_checksum);
    return;
  }
 
  // Extract temperature value
  const uint8_t raw = this->buffer_[6];
 
  // WTS01 encodes sign in bit 7, magnitude in bits 0-6
  const bool negative = (raw & 0x80) != 0;
  const uint8_t magnitude = raw & 0x7F;
 
  const float decimal = static_cast<float>(this->buffer_[7]) / 100.0f;
 
  float temperature = static_cast<float>(magnitude) + decimal;
 
  if (negative) {
    temperature = -temperature;
  }
 
  ESP_LOGV(TAG, "Received new temperature: %.2f°C", temperature);
 
  this->publish_state(temperature);
}
 
}  // namespace esphome::wts01