File content as of revision 0:6f586d7c134c:

#include "mbed.h"

PwmOut EN(p22);
DigitalOut A1(p16);
DigitalOut A2(p17);

Serial pc(USBTX, USBRX);

long float delta_time = 0;
float rpm = 0;
float inc_enc_constant = 0.03125;    // 32 Encoder Ticks per Revolution


Timer t;
// t.read_us() is 32bit interger, max 2^31 - 1 = 2147483647 us = 2147.483647 s = 35.7913941167 min

class Counter
{
public:


    Counter(PinName pin) : _interrupt(pin) {        // create the InterruptIn on the pin specified to Counter
        _interrupt.fall(this, &Counter::increment); // attach increment function of this counter instance
    }


    void increment() {
        delta_time = t.read_us();
        t.reset();

        rpm = ( inc_enc_constant  / (delta_time/1000000) ) *60 ; // rev / m

        _count++;
    }

    int read() {
        return _count;
    }

private:
    InterruptIn _interrupt;
    volatile int _count;
};





Counter counter(p30);   // opto interrupter counter

int main()
{
    pc.baud(115200);
    EN.period(0.020);

    t.start();

    float duty = 0.10;

    while(1) {

        wait(1);

        EN.write(duty);
        duty = duty + 0.01; // increment H-Bridge EN PWM duty cycle 1%
        A1 = 1;         // set H-Bridge input A1 high
        A2 = 0;         // set H-Bridge input A2 low

        // pc.printf("Count so far: %d\n", counter.read());
        // pc.printf("dt: %d\n", delta_time);

        pc.printf("RPM: %f\n", rpm);
        pc.printf("DUTY CYCLE: %f\n",duty);

    }
}