Diff: DigitalFilter.h

Revision:

0:b7a168dd2734

Child:

1:2d33daf35ed1

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/DigitalFilter.h	Wed Sep 10 04:28:53 2014 +0000
@@ -0,0 +1,89 @@
+#ifndef DIGITALFILTER_H
+#define DIGITALFILTER_H
+#include "mbed.h"
+#include "math.h"
+#include<vector>
+
+//enumrator to choose filter type
+typedef enum FilterType{
+         LPF1,
+         LPF2,
+         HPF1,
+         HPF2,
+         RESONANCE,
+         NOTCH,
+         HILBERT,
+}FilterType;  
+                
+class DigitalFilter
+{
+    public:
+        /**
+        * Create a DigitalFilter instance
+        *@param filter_type desired filter type
+        *@param fs sampling frequency
+        */
+        DigitalFilter(FilterType filter_type,float fs);    //constructor, choose filter type and set sampling frequency
+        /**
+        /**
+        * initialize DigitalFilter.Need to set several parameters before calling this method.
+        */
+        int init();                  //calcurate and set filter coefficients.Return value is the delay step of designed filter.
+        /**
+        *Update filter outputs.
+        *@param input latest input of filter
+        */
+        float update(float input);   //update filter outputs. 
+        /**
+        /*Reset buffer of filter
+        */
+        void reset();                //reset filter inputs and past inputs(all past inputs set to 0)
+        /**
+        *accesor of fc(center frequency)
+        *@param fc center frequency
+        */
+        void set_fc(float fc);       //accesor of fc(center frequency)
+        /**
+        *accesor of zeta(decrement)
+        *@param zeta decrement of filter
+        */
+        void set_zeta(float zeta);   //accesor of zeta(decrement)
+        /**
+        *accesor of q(quality factor)
+        *@param q quality factor
+        */
+        void set_Q(float q);       //accesor of quality factor
+        /**
+        *accesor of tap(hilbert filter's tap number)
+        *@param tap hilbert filter's tap number
+        */
+        void set_tap(int tap);     //accesor of hilbert filter's tap number
+        /**
+        *accesor of filter time constant
+        */
+        float get_tau();          //accesor of filter time constant
+        /**
+        *accesor of delay_step
+        */
+        int get_delay_step();        //get delay step of designed filter
+        
+    private:
+        void vectorRightShift(vector<float> &array);   //right shift elements of vector
+        void vectorSetAllToZero(vector<float> &array);      //set all elements of vector to 0
+        vector<float> a_;         //filter coefficients of denominator a
+        vector<float> b_;         //filter coefficients of numerator b
+        vector<float> u_;         //intermediate outputs of filter
+        vector<float> y_;         //intermediate outputs of filter             
+        int delay_step_;        //delay step
+        float gain_;              //filter gain
+        float fs_;                //sampling frequency
+        float ts_;                //sampling time
+        float fc_;                //center frequency
+        float zeta_;              //decrement 
+        float Q_;                 //quality factor
+        float tau_;
+        int tap_;               //tap number of hilbert filter
+        static const float pi_ = 3.141592;          //circular constant
+        FilterType filter_type_ ;
+};
+#endif
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