File content as of revision 0:6f74064686e4:

#include "mbed.h"
#include "ultrasonic-finder.h"

static const char CLS[] = "\x1B[2J";        // VT100 erase screen
static const char HOME[] = "\x1B[H";        // VT100 home
static const int delay = 2;

static const float pulse_line = 4E-5;       // 40 ns
static const int pulse_to_distance = 58;    // 617 / 10.6

enum
{
    DOWN = 0,
    UP = 1
};

int main() 
{
    clear_screen();
    
    Timer timer;
    timer.start();
    
    while (true) 
    {
        send_pulse(trigger);
        while (!echo) {};                  // wait for echo
        float pulse = measure_pulse(timer, echo);
        show_result(pulse);
        wait(delay);
    }        
}

void clear_screen()
{
    pc.printf(CLS);      
    pc.printf(HOME);               
}

void send_pulse(DigitalOut& triggerOut)
{
    triggerOut = UP;
    wait(pulse_line);
    triggerOut = DOWN;
}

float measure_pulse(Timer& timer, const DigitalIn& echoIn)
{
    timer.reset();
    while (echo) {};
    return timer.read_us();
}

void show_result(float pulse)
{
    pc.printf(HOME);    
    pc.printf("Pulse length %6.0f uS\n\r", pulse);
    pulse /= pulse_to_distance;
    pc.printf("\n\rDistance %4.0f cm\n\r", pulse);
}