biquad

1 files changed, 38 insertions, 22 deletions

diff --git a/main.cpp b/main.cpp
index 88447ec..dbce5bf 100755
--- a/main.cpp
+++ b/main.cpp
@@ -1,33 +1,49 @@
+//Using BPF equation from http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt
 
 #include "maximilian.h"
 
-maxiOsc mySine; // This is the oscillator we will use to generate the test tone
-maxiClock myClock; // This will allow us to generate a clock signal and do things at specific times
-double freq; // This is a variable that we will use to hold and set the current frequency of the oscillator
+float xs[3], ys[3];
+float a0, a1, a2, b0, b1, b2;
+float f0 = 400; //THE FREQUENCY
+float Q = 1.0;
 
-void setup() {
+maxiOsc mySwitchableOsc;
+
+void setup() {//some inits
+    double w0 = 2*PI*f0/44100;
+    double alpha = sin(w0)/(2*Q);
+    //Band-pass reson:
+//    b0 =   alpha;
+//     b1 =   0;
+//     b2 =  -1 * alpha;
+//     a0 =   1 + alpha;
+//     a1 =  -2*cos(w0);
+//     a2 =   1 - alpha;
+    
+    //Notch:
+     b0 =   1;
+     b1 =  -2*cos(w0);
+     b2 =   1;
+     a0 =   1 + alpha;
+     a1 =  -2*cos(w0);
+     a2 =   1 - alpha;
     
-    myClock.setTicksPerBeat(1);//This sets the number of ticks per beat
-    myClock.setTempo(120);// This sets the tempo in Beats Per Minute
-    freq=20; // Here we initialise the variable
+    //LPF:
+//    b0 =  (1 - cos(w0))/2;
+//    b1 =   1 - cos(w0);
+//    b2 =  (1 - cos(w0))/2;
+//    a0 =   1 + alpha;
+//    a1 =  -2*cos(w0);
+//    a2 =   1 - alpha;
 }
 
 void play(double *output) {
+    xs[0] = mySwitchableOsc.sawn(400);
+    ys[0] = (b0/a0)*xs[0] + (b1/a0)*xs[1] + (b2/a0)*xs[2]
+    - (a1/a0)*ys[1] - (a2/a0)*ys[2];
     
-    myClock.ticker(); // This makes the clock object count at the current samplerate
-    
-    //This is a 'conditional'. It does a test and then does something if the test is true
-    
-    if (myClock.tick) { // If there is an actual tick at this time, this will be true.
-        
-        freq+=100; // DO SOMETHING
-        
-    } // The curly braces close the conditional
-    
-    //output[0] is the left output. output[1] is the right output
-    
-    output[0]=mySine.sinewave(freq);//simple as that!
-    output[1]=output[0];
+    *output = ys[0];
     
+    ys[2] = ys[1]; ys[1] = ys[0];
+    xs[2] = xs[1]; xs[1] = xs[0];
 }
-