Filter - added AverageFilter - this will be used in place of SumFilter because it removes the possibility of overflows

libraries/Filter/AverageFilter.h

@@ -0,0 +1,82 @@
+// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
+//
+// This is free software; you can redistribute it and/or modify it under
+// the terms of the GNU Lesser General Public License as published by the
+// Free Software Foundation; either version 2.1 of the License, or (at
+// your option) any later version.
+//
+
+/// @file	AverageFilter.h
+/// @brief	A class to provide the average of a number of samples
+///
+///         DO NOT CREATE AND DESTROY INSTANCES OF THIS CLASS BECAUSE THE ALLOC/MALLOC WILL LEAD TO MEMORY FRAGMENTATION
+
+#ifndef AverageFilter_h
+#define AverageFilter_h
+
+#include <inttypes.h>
+#include <Filter.h>
+
+// 1st parameter <T> is the type of data being filtered.  
+// 2nd parameter <U> is a larger data type used during summation to prevent overflows
+template <class T, class U>
+class AverageFilter : public Filter<T>
+{
+  public:
+	AverageFilter(uint8_t requested_size) : Filter<T>(requested_size) {};
+
+	// apply - Add a new raw value to the filter, retrieve the filtered result
+	virtual T apply(T sample);
+
+	// reset - clear the filter
+	virtual void reset();
+
+  private:
+	uint8_t	_num_samples;
+};
+
+// Typedef for convenience (1st argument is the data size, 2nd argument is a datasize that's bigger to handle overflows)
+typedef AverageFilter<int8_t, int16_t> AverageFilterInt8;
+typedef AverageFilter<uint8_t, uint16_t> AverageFilterUInt8;
+typedef AverageFilter<int16_t, int32_t> AverageFilterInt16;
+typedef AverageFilter<uint16_t, uint32_t> AverageFilterUInt16;
+typedef AverageFilter<int32_t, float> AverageFilterInt32;
+typedef AverageFilter<uint32_t, float> AverageFilterUInt32;
+
+// Public Methods //////////////////////////////////////////////////////////////
+
+template <class T, class U>
+T AverageFilter<T,U>::apply(T sample)
+{
+	U result = 0;
+
+	// call parent's apply function to get the sample into the array
+	Filter<T>::apply(sample);
+
+	// increment the number of samples so far
+	_num_samples++;
+	if( _num_samples > Filter<T>::filter_size || _num_samples == 0 )
+		_num_samples = Filter<T>::filter_size;
+
+	// get sum of all values - there is a risk of overflow here that we ignore
+	for(int8_t i=0; i<Filter<T>::filter_size; i++)
+		result += Filter<T>::samples[i];
+
+	return (T)(result / _num_samples);
+}
+
+// reset - clear all samples
+template <class T, class U>
+void AverageFilter<T,U>::reset()
+{
+	// call parent's apply function to get the sample into the array
+	Filter<T>::reset();
+
+	// clear our variable
+	_num_samples = 0;
+}
+
+#endif
+
+
+