Diff: filter.cpp

Revision:

0:09ae59836ddc

Child:

1:db5970567c4d

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/filter.cpp	Wed Oct 25 12:35:24 2017 +0000
@@ -0,0 +1,54 @@
+#include "filter.h"
+
+float LowPass::filter(float x) // same as function lowpass
+{
+   float y = a * yprev + (1 - a) * x;
+   yprev = y;
+   return y;
+}
+
+float HighPass::filter(float x){
+    xprev[0] = xprev[1];             // renew the 'previous value'
+    xprev[1] = x;                    // 2nd value is the current input value
+   
+    float y = a * yprev + a * (xprev[1] - xprev[0]); // according to: https://en.wikipedia.org/wiki/High-pass_filter
+    yprev = y;                       // renew yprev for the next time
+    return y;
+}
+
+float Notch::filter(float x){
+    xprev[0] = xprev[1];
+    xprev[1] = xprev[2];
+    xprev[2] = x;
+                                                                                           
+    float y = (
+                (1.0+pow(lambda,2))*x
+                - 2.0*(1.0-pow(lambda,2))*xprev[1]
+                +(1.0+pow(lambda,2))*xprev[0]
+                + 2.0*(1.0-pow(lambda,2))*yprev[1]
+                -(1.0+pow(lambda,2)-b)*yprev[0]
+            )
+            /(1.0+pow(lambda,2)+b);
+    
+    yprev[0] = yprev[1];
+    yprev[1] = y;
+    return y;
+}
+
+float ButterLow::filter(float x){
+    xprev[0] = xprev[1];
+    xprev[1] = xprev[2];
+    xprev[2] = x;
+    
+    float y =   (pow(w,2)*x
+                + 2*w*xprev[1]
+                + pow(w,2)*xprev[0]
+                + (2+sqrt(2.0f)*w-2*pow(w,2))*yprev[1]
+                - (1+pow(w,2))*yprev[0]
+                )
+                /(1+sqrt(2.0f)*w+pow(w,2));
+
+    yprev[0] = yprev[1];
+    yprev[1] = y;
+    return y;
+}
\ No newline at end of file