void setup() {
  Serial.begin(115200);
  Serial.println("Piecewise Linear Approximations for Sensor");
}

void loop() {
  static int pre_adc = -1;  // Initialize to invalid value to force first print
  int adc_value = analogRead(36);

  // Only update if ADC value changes (noise filtering)
  if (adc_value != pre_adc) {
    pre_adc = adc_value;

    // Convert ADC to voltage
    float v_adc = 3.3 * adc_value / 4095;
    float v_sensor = 0;

    // Piecewise linear approximation
    if (v_adc <= 0.5)
      v_sensor = 20.0 * v_adc;
    else if (v_adc <= 2.5)
      v_sensor = 2.0 * v_adc + 9.0;
    else
      v_sensor = 5.6 * v_adc + 7.75;

    Serial.printf("V_sensor=%.3fV, V_adc=%.3fV\n", v_sensor, v_adc);
  }

  delay(10);
}