Diff: read_filter_new.cpp

Revision:

3:11c2175b4478

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/read_filter_new.cpp	Mon Oct 26 11:42:17 2015 +0000
@@ -0,0 +1,122 @@
+#include "mbed.h"
+#include "read_filter_emg.h"
+//included for fabs() function
+#include <math.h>
+
+//input (u) = analogin
+
+AnalogIn(/*pin-name*/) = &aI;
+input = aI.read();
+
+double v1=0;
+double v2=0;
+
+//general biquad filter that can be called in all the filter functions
+double biquad(double u, double &v1, double &v2, const double a1,
+                    const double a2, const double b0, const double b1, const double b2)
+{
+    double v = u * a1*v1 * a2*v2;
+    double y = b0*v + b1*v1 + b2*v2;
+    //values of v2 and v1 are updated, as they are passed by reference
+    //they update globally
+    v2 = v1; v1 = v;
+    return y;
+}
+
+//Specifying filter coefficients highpass
+
+   /* high pass filter consists of three cascaded biquads
+    blow coefficients for those three biquads */
+    //first high pass biquad
+    const double highp1_a1 = -0.67538034389;
+    const double highp1_a2 = 0.12769255668;
+    const double highp1_b0 = 1.00000000000;
+    const double highp1_b1 = -2.00000000000;
+    const double highp1_b2 = 1.00000000000;
+
+    //second high pass biquad
+    const double highp2_a1 = -0.76475499450;
+    const double highp2_a2 = 0.27692273367;
+    const double highp2_b0 = 1.00000000000;
+    const double highp2_b1 = -2.00000000000;
+    const double highp2_b2 = 1.00000000000;
+
+    //third high pass biquad
+    const double highp3_a1 = -0.99216561242;
+    const double highp3_a2 = 0.65663360837;
+    const double highp3_b0 = 1.00000000000;
+    const double highp3_b1 = -2.00000000000;
+    const double highp3_b2 = 1.00000000000;
+    
+//Specifying filter coefficients lowpass
+
+    /* lowpass filter consists of three cascaded biquads
+    below the coefficients for those three biquads */
+    //first high pass biquad
+    const double lowp1_a1 = -1.05207469728;
+    const double lowp1_a2 = 0.28586907478;
+    const double lowp1_b0 = 1.00000000000;
+    const double lowp1_b1 = 2.00000000000;
+    const double lowp1_b2 = 1.00000000000;
+
+    //second high pass biquad
+    const double lowp2_a1 = -1.16338171052;
+    const double lowp2_a2 = 0.42191097989;
+    const double lowp2_b0 = 1.00000000000;
+    const double lowp2_b1 = 2.00000000000;
+    const double lowp2_b2 = 1.00000000000;
+
+    //third high pass biquad
+    const double lowp3_a1 = -1.42439823874;
+    const double lowp3_a2 = 0.74093118112;
+    const double lowp3_b0 = 1.00000000000;
+    const double lowp3_b1 = 2.00000000000;
+    const double lowp3_b2 = 1.00000000000;
+    
+//input to each filter is output of the filter before(excl. first which uses input_sample)
+    /* NOT SURE IF PASSING V1 AND V2 IS CORRECT,
+    WILL IT UPDATE IN THE MEMORY POSITION SO THAT
+    V1 IS CHANGED GLOBALLY */
+    
+//highpass
+
+double highpass_filter(double input)
+{
+    double y1 = biquad(input, v1, v2, highp1_a1, highp1_a2, highp1_b0, highp1_b1, highp1_b2);
+    double y2 = biquad(y1, v1, v2, highp2_a1, highp2_a2, highp2_b0, highp2_b1, highp2_b2);
+    double y3 = biquad(y2, v1, v2, highp3_a1, highp3_a2, highp3_b0, highp3_b1, highp3_b2); 
+    
+    return y3;
+}
+    
+    
+//rectifier
+double rectify(double y3)
+{
+    y3 = fabs(y3);
+    return y3;
+}
+
+//lowpass
+
+double lowpass_filter(double y3)
+{
+    double y4 = biquad(y3, v1, v2, lowp1_a1, lowp1_a2, lowp1_b0, lowp1_b1, lowp1_b2);
+    double y5 = biquad(y4, v1, v2, lowp2_a1, lowp2_a2, lowp2_b0, lowp2_b1, lowp2_b2);
+    double filtered_signal = biquad(y5, v1, v2, lowp3_a1, lowp3_a2, lowp3_b0, lowp3_b1, lowp3_b2);
+    
+    return filtered_signal;
+}
+
+double filter(double input)
+{
+    /* function passes the input through the three filters
+    returns the final output value as filtered sample
+    this is used in check_state() function to determine state of system
+    */
+    double y1 = highpass_filter(input);
+    double y2 = rectify(y3);
+    double filtered_signal = lowpass_filter(y3);
+
+    return filtered_signal;
+}
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