File content as of revision 27:869ec80f2bf7:

#include "mbed.h"
#include "HIDScope.h"
#include "BiQuad.h"
#include "math.h"
#define EMG_DEBUG
#ifndef M_PI
#define M_PI    3.14159265358979323846
#endif

#define EMG_THRESHOLD   0.2

class EMG_input {
    private:
        AnalogIn emg0;     // Declare port
        BiQuad bq1, bq2, bq3, bq4, bq5, bq6, bq7, bq8;  // Declare biquads
        BiQuadChain bqc1, bqc2;  // Declare biquad chains
        double maxsig;        
    public:
        double e0, e0f, e0flow, discrete;
        EMG_input(PinName pin);
        void tick(void);
        bool read(void);
        ~EMG_input();
        
};

EMG_input::EMG_input(PinName pin) : emg0(pin),
    bq1(9.755715E-01, -1.951143E+00, 9.755715E-01, 1.000000E+00, -1.949216E+00, 9.530699E-01),   // High pass 10 Hz (4th order)
    bq2(9.442373E-01, -1.888475E+00, 9.442373E-01, 1.000000E+00, -1.886610E+00, 8.903397E-01),
    bq3(9.955670E-01, -1.893718E+00, 9.955670E-01, 1.000000E+00, -1.890851E+00, 9.910331E-01),   // Notch (stop band) 49 - 51 Hz (4th order)
    bq4(9.955670E-01, -1.893718E+00, 9.955670E-01, 1.000000E+00, -1.896548E+00, 9.912741E-01),
    bq5(4.798613E-01, 9.597225E-01, 4.798613E-01, 1.000000E+00, 4.531195E-01, 4.663256E-01),     // Low pass 300 Hz (4th order)
    bq6(3.483908E-01, 6.967817E-01, 3.483908E-01, 1.000000E+00, 3.289757E-01, 6.458765E-02),
    bq7(8.818771E-05, 1.763754E-04, 8.818771E-05, 1.000000E+00, -1.985325E+00, 9.856773E-01),    // Low pass 3Hz on rectified signal (4th order)
    bq8(8.730353E-05, 1.746071E-04, 8.730353E-05, 1.000000E+00, -1.965420E+00, 9.657687E-01),
    maxsig(0) {
    bqc1.add(&bq1).add(&bq2).add(&bq3).add(&bq4).add(&bq5).add(&bq6);    // Add filters to filter chain
    bqc2.add(&bq7).add(&bq8);    // Add filters to filter chain   
}


void EMG_input::tick(void){
    double e0 = emg0.read();    // Read emg signal
    double e0f = fabs(bqc1.step(e0));    // Filter signal, rectify
    double e0flow = bqc2.step(e0f); // Low pass filter rectified emg signal
    if (e0flow>maxsig){ maxsig = e0flow;}   // Remember maximum peak (used for calibrating signal)
    double discrete = floor(sqrt(e0flow/maxsig)*10.0)/10.0;    // Discretise signal non linearly (low muscle activity means higher gain on the input signal, sqrt used as envelope)
}

bool EMG_input::read(void){
    return (discrete>=EMG_THRESHOLD)?true:false; 
}

EMG_input::~EMG_input(){
}