File content as of revision 5:2ae500da8fe1:

#include "mbed.h"
#include "MODSERIAL.h"
#include "FastPWM.h"
#include "QEI.h"
#include <math.h>

DigitalIn button1(D12);
AnalogIn pot2(A0);
Ticker john;
DigitalOut motor1Direction(D7);
FastPWM motor1Velocity(D6);
Serial pc(USBTX, USBRX);
QEI Encoder(D8,D9,NC,8400);
volatile double frequency = 17000.0;
volatile double period_signal = 1.0/frequency;
float vel = 0.0f;
float referencevelocity;
float motorvalue2;
double Kp = 17.5;
int counts;
float position1 = 0;
float position2;
float timeinterval = 0.001;
float measuredvelocity;

// README
// positive referencevelocity corresponds to a counterclockwise motion


//P control implementation (behaves like a spring)
double P_controller(double error)
{
    //Proportional part:
    double u_k = Kp * error;
    
    //sum all parts and return it
    return u_k;
}

//get the measured velocity
double getmeasuredvelocity()
{   
    counts = Encoder.getPulses();
    counts = counts % 8400;
    position2 = counts/8400*2*3.141592;
    measuredvelocity = (position2-position1)/timeinterval; 
    position1 = position2;
}

//get the reference of the velocity: positive or negative
double getreferencevelocity()
{
    referencevelocity = -1.0 + 2.0*pot2.read();
    return referencevelocity;
}   

//send value to motor
void sendtomotor(float motorvalue)
{   
    motorvalue2 = motorvalue;
    vel = fabs(motorvalue);
    vel = vel > 1.0f ? 1.0f : vel;   
    motor1Velocity = vel;

    motor1Direction = (motorvalue > 0.0f);
}

// function to call reference velocity, measured velocity and controls motor with feedback
void measureandcontrol(void)
{
    float referencevelocity = getreferencevelocity();
    float measuredvelocity = getmeasuredvelocity();
    sendtomotor(referencevelocity);
}
int main()
{
    pc.baud(115200);
    pc.printf("Starting...\r\n");
    motor1Velocity.period(period_signal);
    john.attach(measureandcontrol, timeinterval);
    while(true)
    {
        wait(0.5);
        //pc.printf("velocity = %f\r\n", vel);
        //pc.printf("motor1Direction = %i\r\n", (int)motor1Direction);
        //pc.printf("motorvalue2 = %f\r\n", motorvalue2);
        pc.printf("number of counts %i\r\n", counts);
        pc.printf("measured velocity is %f\r\n", measuredvelocity);
        pc.printf("position1 = %f\r\n",position1);
        pc.printf("position2 = %f\r\n",position2);
    }
}