Thijs van Aalten / Olimex_wrapper

ya kno it

Dependencies:   Filters

emg.cpp@0:850bf2d90868, 2017-10-25 (annotated)

Committer:
Thijs12va
Date:
Wed Oct 25 12:35:29 2017 +0000
Revision:
0:850bf2d90868
Child:
2:02d31a0caac1
a

Who changed what in which revision?

UserRevisionLine numberNew contents of line
Thijs12va 0:850bf2d90868 1 #include "emg.h"
Thijs12va 0:850bf2d90868 2
Thijs12va 0:850bf2d90868 3 emg_shield::emg_shield(PinName pin,float fs):emg_in(pin)
Thijs12va 0:850bf2d90868 4 {
Thijs12va 0:850bf2d90868 5 highpass.a=0.05; // filter coefficient of high-pass filter
Thijs12va 0:850bf2d90868 6 float lambda= 51.6 *2.0*3.1415; // 50 Hz notch filter frequency in rad/s (Hz*2*pi)
Thijs12va 0:850bf2d90868 7 float b= 4.0 *2.0*3.1415; // 50 Hz notch filter bandwidth in rad/s (Hz*2*pi)
Thijs12va 0:850bf2d90868 8 notch50.lambda = lambda/(2.0*fs); // scaling for the 2/T multiplication which happens in the transform from s-domain to z-domain
Thijs12va 0:850bf2d90868 9 notch50.b = b/(2.0*fs); // scaling for the 2/T multiplication which happens in the transform from s-domain to z-domain
Thijs12va 0:850bf2d90868 10 float lambda2=103.2 *2.0*3.1415; // 100 Hz notch filter frequency in rad/s (Hz*2*pi)
Thijs12va 0:850bf2d90868 11 float b2= 4.0 *2.0*3.1415; // 100 Hz notch filter frequency in rad/s (Hz*2*pi)
Thijs12va 0:850bf2d90868 12 notch100.lambda = lambda2/(2.0*fs); // scaling for the 2/T multiplication which happens in the transform from s-domain to z-domain
Thijs12va 0:850bf2d90868 13 notch100.b = b2 /(2.0*fs); // scaling for the 2/T multiplication which happens in the transform from s-domain to z-domain
Thijs12va 0:850bf2d90868 14 float wc = 10 *2.0*3.1415; // butterworth filter cutoff frequency in rad/s (Hz*2*pi)
Thijs12va 0:850bf2d90868 15 butter.w = wc/(2.0f*fs);
Thijs12va 0:850bf2d90868 16 Value=0;
Thijs12va 0:850bf2d90868 17 butter.yprev[0]=0;
Thijs12va 0:850bf2d90868 18 butter.yprev[1]=0;
Thijs12va 0:850bf2d90868 19 butter.xprev[2]=0;
Thijs12va 0:850bf2d90868 20 butter.xprev[0]=0;
Thijs12va 0:850bf2d90868 21 butter.xprev[1]=0;
Thijs12va 0:850bf2d90868 22 tick.attach(this,&emg_shield::tickFunction, 1.0f/fs);
Thijs12va 0:850bf2d90868 23 }
Thijs12va 0:850bf2d90868 24
Thijs12va 0:850bf2d90868 25 void emg_shield::tickFunction(){
Thijs12va 0:850bf2d90868 26 float raw_data = emg_in.read(); // obtain raw EMG data
Thijs12va 0:850bf2d90868 27
Thijs12va 0:850bf2d90868 28 float emg_notch = notch50.filter(raw_data); // notch filter to filter out the noise (especially from laptop charger)
Thijs12va 0:850bf2d90868 29
Thijs12va 0:850bf2d90868 30 float emg_hp = highpass.filter(emg_notch); // high-pass filter
Thijs12va 0:850bf2d90868 31
Thijs12va 0:850bf2d90868 32 float emg_hp_abs = fabs(emg_hp); // full wave rectification
Thijs12va 0:850bf2d90868 33
Thijs12va 0:850bf2d90868 34 //float emg_envelope = lowpass.filter(emg_hp_abs); // 2 1st order low-pass filters
Thijs12va 0:850bf2d90868 35 //emg_envelope = lowpass2.filter(emg_envelope);
Thijs12va 0:850bf2d90868 36 float emg_envelope = butter.filter(emg_hp_abs); // or 1 2nd order (butterworth) low-pass filter
Thijs12va 0:850bf2d90868 37
Thijs12va 0:850bf2d90868 38 Value = emg_envelope;
Thijs12va 0:850bf2d90868 39 }
Thijs12va 0:850bf2d90868 40
Thijs12va 0:850bf2d90868 41 float emg_shield::GetValue(){
Thijs12va 0:850bf2d90868 42 return Value;
Thijs12va 0:850bf2d90868 43 }
Thijs12va 0:850bf2d90868 44