Unexpected variable behaviour

Projects Programming
1

Hello,

I wrote a simple code to average out analogRead values during exact timing periods.

const int mVperAmp = 100; // use 185 for 5A Module, and 66 for 30A Module
float Vref  = 5.00; //read your Vcc voltage,typical voltage should be 5000mV(5.0V)
//float Vref  = 1.10;

boolean firstFlag = true;
boolean timerResetFlag = true;

float measValue_1[10];
float measAverage_1 = 0.0;
float measValue_2[10];
float measAverage_2 = 0.0;
float mAh = 0.0;

int sampleCounter = 0;
int secCounter = 0;
int minCounter = 0;
int adcValue[2] = {0, 0};
int prevAdc[2] = {0, 0};
int runAdc[2] = {0, 0};

unsigned long sampleStarted = 0;
unsigned long averageStarted = 0;
unsigned long averageComplete = 0;
unsigned long averageTime = 0;

void setup()
{
  analogReference(DEFAULT);
  //analogReference(INTERNAL);
  Serial.begin(9600);
  sampleStarted = millis();
}

void loop()
{
  if ( (millis() - sampleStarted) < 90)
  {
    if (firstFlag == true)
    {
      sampleStarted = millis();
      if (sampleCounter == 0)
      {
        averageStarted = millis();
        Serial.print(averageStarted);
        Serial.println("ms, Start occured.");
      }
      prevAdc[1] = analogRead(A0);
      prevAdc[2] = analogRead(A1);
      firstFlag = false;
    }
    adcValue[1] = analogRead(A0);
    runAdc[1] = round( float(prevAdc[1] + adcValue[1]) / 2.0);
    prevAdc[1] = runAdc[1];
    adcValue[2] = analogRead(A1);
    runAdc[2] = round( float(prevAdc[2] + adcValue[2]) / 2.0);
    prevAdc[2] = runAdc[2];
  }
  else
  {

    //measValue_1[sampleCounter] = ( (float(runAdc) / 1024.0) * Vref - (Vref / 2.0)) * 5.4054;  //Sensitivity:185mV/A, 0A @ Vcc/2
    measValue_1[sampleCounter] = (float(runAdc[1]) / 1024.0);
    measValue_2[sampleCounter] = (float(runAdc[2]) / 1024.0);
    runAdc[1] = 0;
    runAdc[2] = 0;
    sampleCounter += 1;

    if (sampleCounter != 10)
    {
      while ((millis() - sampleStarted) < 100)
      {
        //wait for complete 100ms
      }
    }

    else
    {
      //Serial.println("average completed.");
      secCounter += 1;
      if (secCounter == 60)
      {
        minCounter += 1;
        secCounter = 0;
      }
      for (int i = 0; i <= 9; i++)
      {
        //Serial.println(measValue_1[i]);
        measAverage_1 += measValue_1[i];
        measValue_1[i] = 0.0;
        measAverage_2 += measValue_2[i];
        measValue_2[i] = 0.0;
      }

      sampleCounter = 0;
      measAverage_1 = measAverage_1 / 10.0;
      measAverage_2 = measAverage_2 / 10.0;
//      printTime();
//      Serial.print(measAverage_1 * Vref, 5); Serial.print("V --> ");
//      Serial.print(measAverage_2 * Vref, 5); Serial.print("V --> ");
//      Serial.print(((1 - ((measAverage_2 / measAverage_1) / 2)) * 100), 3); Serial.println("% error");

      //      if (measAverage_1 >= 0.1)
      //      {
      //        if (timerResetFlag == true)
      //        {
      //          secCounter = 0;
      //          minCounter = 0;
      //          timerResetFlag = false;
      //        }
      //        Serial.print(" --> ");
      //        mAh += (measAverage_1 * 10000) / 3600;
      //        Serial.print(mAh / 10, 4); Serial.println(" mAh");
      //      }
      //      else
      //      {
      //        mAh = 0.0;
      //        if (timerResetFlag == false)
      //        {
      //          secCounter = 0;
      //          minCounter = 0;
      //          timerResetFlag = true;
      //        }
      //        Serial.println();
      //      }
      
      measAverage_1 = 0.0;
      measAverage_2 = 0.0;
      while ((millis() - sampleStarted) < 100)
      {
        //wait for complete 100ms
      }
      averageTime = (millis() - averageStarted);
      Serial.print(millis());Serial.print(" ");Serial.print(averageStarted);Serial.print(" ");
      Serial.print(averageTime); Serial.println(" ms");
    }

    firstFlag = true;
    sampleStarted = millis();
  }
}

void printTime()
{
  if (minCounter < 10)
  {
    Serial.print("0");
  }
  Serial.print(minCounter);
  Serial.print(":");
  if (secCounter < 10)
  {
    Serial.print("0");
  }
  Serial.print(secCounter); Serial.print(" --> ");

}

My concern is, that averageStarted variable acts unexpectedly. After firstFlag condition is checked, it seems OK, I get "Start occured." message every 1000ms. But at the end of the loop, when I try to calculate the averageTime, the averageStarted seems to have zero value first, then after every 66 second, it increments with 2^16 (unsigned int?).

I don't get it, besides averageStarted = millis(); the code is not intended to modify the averageStarted variable.
Can somebody tell me what could cause this?

Thanks in advance,
Arpad

2

You declare these variables as arrays of size 2

int adcValue[2] = {0, 0};
int prevAdc[2] = {0, 0};
int runAdc[2] = {0, 0};

But your code references and assigned to the 3rd element

      prevAdc[1] = analogRead(A0);
      prevAdc[2] = analogRead(A1);

so you are stomping on some other memory, probably your variable that is acting odd.

3

To add to what blh64 said, arrays are zero indexed. If you have an array of two elements like your adcValue, the first element is adcValue[0] and the second element is adcValue[1].

4

Oh, what a dumb mistake. Thanks for the open-eyed inspection.
I used array indexing correctly for e.g. measValue_1[], but managed to take a wrong turn with adc arrays. Thanks again, lesson learned.