Arduino template for polling analog voltages at given interval

adc_worker.ino

// Ben Fasoli

const int n = 6;
const int pins[n] = {A0, A1, A2, A3, A4, A5};
const float slope[n] = {1, 1, 1, 1, 1, 1};
const float intercept[n] = {0, 0, 0, 0, 0, 0};

// Board reference voltage measured on aref pin
const float refVoltage = 4.93;  // V

// Schedule sampling interval
const long interval = 1000;  // ms

// Sets oversampling precision
// Without modifying ADC prescaler, the analogRead built-in takes 100-us per
// iteration. 64 samples occur over a duration of 6.4-ms for each analog channels
// so a single "observation" occurs over a 38.4-ms interval.
int numSample = 64;  // 13-bit

unsigned long prevMillis = 0;  // ms


void setup() {
  Serial.begin(9600);
}

void loop() {
  // Execute main() every interval ms
  if (millis() - prevMillis >= interval) {
    prevMillis = millis();
    main();
  }
}

void main() {
  // Reads analog voltages from all defined pins using oversample(pin) and
  // linearly rescales the voltage using the user defined slope and intercept
  for (int i = 0; i < n; i++) {
    float voltage = oversample(pins[i]);
    float value = (voltage * slope[i]) + intercept[i];
    
    Serial.print(value);
    if (i < (n - 1)) {
      Serial.print(',');
    }
  }
  
  Serial.println();
}

float oversample(int pin) {
  // ADC oversampling based on AVR121
  // https://www.microchip.com/wwwAppNotes/AppNotes.aspx?appnote=en591540
  //
  // Reads analog pin numSample times and returns the average voltage
  float voltageSum = 0;
  
  for (int j = 0; j < numSample; j++) {
    voltageSum += analogRead(pins[i]);
  }
  
  return (voltageSum / numSample) * (5.0 / refVoltage) / 1023.0;
}