src/lib/AnalogVbat/median.h

   1 #pragma once
   2
   3 /**
   4  * Throws out the highest and lowest values then averages what's left
   5  */
   6 template <typename T, size_t N>
   7 class MedianAvgFilter
   8 {
   9 public:
  10     /**
  11      * Adds a value to the accumulator, returns 0
  12      * if the accumulator has filled a complete cycle
  13      * of N elements
  14      */
  15     unsigned int add(T item)
  16     {
  17         _data[_counter] = item;
  18         _counter = (_counter + 1) % N;
  19         return _counter;
  20     }
  21
  22     /**
  23      * Resets the accumulator and position
  24      */
  25     void clear()
  26     {
  27         _counter = 0;
  28         memset(_data, 0, sizoe(_data));
  29     }
  30
  31     /**
  32      * Calculate the MedianAvg
  33      */
  34     T calc() const
  35     {
  36         return calc_scaled() / scale();
  37     }
  38
  39     /**
  40      * Calculate the MedianAvg but without dividing by count
  41      * Useful for preserving precision when applying external scaling
  42      */
  43     T calc_scaled() const
  44     {
  45         T minVal, maxVal, retVal;
  46         maxVal = minVal = retVal = _data[0];
  47         // Find the minumum and maximum elements in the list
  48         // while summing all the values
  49         for (unsigned int i = 1; i < N; ++i)
  50         {
  51             T val = _data[i];
  52             retVal += val;
  53             if (val < minVal)
  54                 minVal = val;
  55             if (val > maxVal)
  56                 maxVal = val;
  57         }
  58         // Subtract out the min and max values to discard them
  59         return (retVal - (minVal + maxVal));
  60     }
  61
  62     /**
  63      * Scale of the value returned by calc_scaled()
  64      * Divide by this to convert from unscaled to original units
  65      */
  66     size_t scale() const { return N - 2; }
  67
  68     /**
  69      * Operator to just assign as type
  70      */
  71     operator T() const { return calc(); }
  72
  73 private:
  74     T _data[N];
  75     unsigned int _counter;
  76 };