CODEWITHSUNDEEP
cpic
NewLook
NewLook

Reputation: 33

Filter readings PIC

I am using a PIC and a proximity sensor to read the distance in cm away from an object.

The result is stored in

Distance = Rf_Rx_Buff[6].

Basically instead of using that result I want to implement a filter which takes 10 readings, averages them out and only allows the average to be read out in Rf_Rx_Buff[6] .

Could anyone guide me on how to implement this.

Upvotes: 2

Views: 109

Answers (2)

chux
chux

Reputation: 154075

At least 3 approaches:

  1. Read 10 values and return the average (easy)

    unsigned Distance1(void) {
  unsigned Average_Distance = 0;
  for (int i=0; i<10; i++) {
    Average_Distance += Rf_Rx_Buff[6];
  }
  Average_Distance = (Average_Distance + 5)/10;  // +5 for rounding
  return Average_Distance;
}

  2. Read once, but return the average of the last 10 reads:

    unsigned Distance2(void) {
  static unsigned Distance[10];
  static unsigned Count = 0;
  static unsigned Index = 0;
  Distance[Index++] = Rf_Rx_Buff[6];
  if (Index >= 10) {
    Index = 0;
  }
  Count++;
  if (Count > 10) {
    Count = 10;
  }
  unsigned long Average_Distance = 0;
  for (int i=0; i<10; i++) {
    Average_Distance += Distance[i];
  }
  Average_Distance = (Average_Distance + Count/2)/Count;
  return Average_Distance;
}

  3. Read once, but return the the running average (digital low pass filter):

    unsigned Distance3(void) {
  static unsigned long Sum = 0;
  static int First = 1;
  if (First) {
    First = 0;
    Sum =  Rf_Rx_Buff[6] * 10;
  } else {
    Sum = Rf_Rx_Buff[6] + (Sum*9)/10;
  }
  return (Sum + 5)/10;
}

Other simplifications and approaches possible,

Upvotes: 1

code monkey
code monkey

Reputation: 2124

You could do it that way:

1.) Develop a function that calculates the average.

int calc_average(int *sensor_values, int number_sensor_values) {
    int result = 0;
    for(char i = 0; i < number_sensor_values; ++i) {
        // calculate average
        result += *sensor_values++...
        ....
    }
    ....
    return result;
}

2.) Read 10 sensor data and store the data in an array (sensor_values).

3.) Call your calc_average function and pass the sensor_values array to get the result.

Upvotes: 0

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