Diff: Filter.h

Revision:

40:8e852115fe55

Child:

46:fd5a62296b12

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Filter.h	Tue May 26 11:28:37 2015 +0000
@@ -0,0 +1,103 @@
+#ifndef _H_FILTER_H
+#define _H_FILTER_H
+
+#include "Utils.h"
+
+/// \brief Low-pass filters an incoming stream of numbers.
+/// Implements a 1st-order IIR low-pass filter. The coefficient can be used to specify
+/// how much to filter.
+class LowPassFilter
+{
+protected:
+    float y;
+    float const alpha;
+    
+public:
+    /// Construct the filter with given coefficient.
+    /// @param a filter coefficient (0.0 to 1.0), higher values result in more filtering.
+    LowPassFilter(float const a) : y(0), alpha(a) {}
+    
+    /// Main processing function, passes given value to filter and returns the filter's output.
+    /// Call repeatedly to filter an incoming stream of numbers.
+    /// @param x one value to send to filter as input
+    /// @return filtered output
+    float filter(float const x)
+    {
+        y = x + alpha * (y - x);
+        return y;
+    }
+    
+    /// Resets the internal state of the filter. Use to start filtering a new stream.
+    void reset()
+    {
+        y = 0;
+    }
+};
+
+/// 1st order high-pass filter.
+/// Used in exactly the same way as LowPassFilter, except that it's a high-pass. @see LowPassFilter
+class HighPassFilter
+{
+protected:
+    float y;
+    float x_1;
+    float const alpha;
+
+public:
+    HighPassFilter(float const a) : y(0), x_1(0), alpha(1 - a) {}
+    float filter(float const x)
+    {
+        y = alpha * (y + x - x_1);
+        x_1 = x;
+        return y;
+    }
+    void reset()
+    {
+        y = 0;
+        x_1 = 0;
+    }
+};
+
+class Integrator
+{
+protected:
+    float y;
+    float dt;
+    float clipmax;
+    
+public:
+    Integrator( float const _dt = 1,
+                float const initial = 0,
+                float const _max = 1000000) : y(initial),
+                                    dt(_dt),
+                                    clipmax(_max) {}
+    float integrate(float const x)
+    {
+        return (y = utils::clip(-clipmax, y + x * dt, clipmax));
+    }
+    void reset(float const _dt = 1, float const initial = 0)
+    {
+        y = initial;
+        dt = _dt;
+    }
+};
+
+class Differentiator
+{
+protected:
+    float y;
+    
+public:
+    Differentiator() : y(0) {}
+    float differentiate(float const x)
+    {
+        return (y = x - y);
+    }
+    
+    void reset()
+    {
+        y = 0;
+    }
+};
+
+#endif//_H_FILTER_H
\ No newline at end of file