#include <Arduino.h>

// ========== پارامترهای مدار ==========
#define VREF_ADC        3.3f
#define ADC_RESOLUTION  4095.0f
#define R1              1448.0f
#define R2              1566.0f
#define VCC_SENSOR      4.67f
#define RL_SENSOR       10000.0f
#define R0              139160.0f    // ← مقدار R0 بدست‌آمده از کالیبراسیون (بر حسب اهم)
#define CO_A            1.9f        // ضریب A در فرمول ppm = A * (Rs/R0)^B
#define CO_B            -0.6f       // ضریب B (معمولاً منفی)
#define ADC_PIN         A2
#define NUM_SAMPLES     10

// =====================================

float readSensorVoltage() {
  uint32_t sum = 0;
  for (int i = 0; i < NUM_SAMPLES; i++) {
    sum += analogRead(ADC_PIN);
    delay(10);
  }
  float adcValue = sum / (float)NUM_SAMPLES;
  float vAdc = (adcValue / ADC_RESOLUTION) * VREF_ADC;
  return vAdc * (R1 + R2) / R2;
}

float calculateRs(float vOut) {
  if (vOut <= 0.0f) return 0.0f;
  return RL_SENSOR * (VCC_SENSOR / vOut - 1.0f);
}

float calculatePPM(float rs) {
  float ratio = rs / R0;
  if (ratio <= 0.0f) return 0.0f;
  return CO_A * pow(ratio, CO_B);
}

void setup() {
  Serial1.begin(115200);
  analogReadResolution(12);
  pinMode(ADC_PIN, INPUT);

  Serial1.println("MQ7 CO Measurement");
  Serial1.print("R0 = "); Serial1.print(R0); Serial1.println(" ohms");
  Serial1.println("Starting...\n");
  delay(3000);
}

void loop() {
  float vOut = readSensorVoltage();
  float rs = calculateRs(vOut);
  float ppm = calculatePPM(rs);
  Serial1.print("CO = "); Serial1.print(ppm, 1); Serial1.println(" ppm");
  delay(2000);
}