File content as of revision 2:12da800fd10a:

#include "mbed.h"
#include "Ultrasonic.h"


float DistanceCM = 0;
DigitalOut trigger(TRIGGER);
InterruptIn echo(ECHO);       // Attach interrupt to the echo pin
Timer timer;
Ticker tick;
Timeout timeout;

/*
* Call this function and it will return the distance in centimeter
*/
float read_cm()
{
    return DistanceCM;
}


void start()
{
    timer.start();
}

void stop()
{
    DistanceCM = timer.read_us()/58;
    timer.stop();
    //pc.printf("Distance: %f \n", DistanceCM);
    timer.reset();
    timeout.detach();
}

void trig()
{
    timeout.attach(&timeout_err, 0.05);
    trigger = 1;
    wait_us(10);
    trigger = 0;
}


void Ultrasonic_init()
{
    timer.reset();
    echo.rise(&start);
    echo.fall(&stop);
    tick.attach(&trig,0.06);
}

void timeout_err()
{
    // Timeout elapsed -> there is some problem
    // out the distance to zero to highligth error
    
    DistanceCM = 0;
}