File content as of revision 1:47d9d1523dfa:

#include "mbed.h"
#include "TextLCD.h"

float measure();

int main()
{

    TextLCD lcd(PTE30, PTE29, PTE23, PTE22, PTE21, PTE20); // rs, e, d4-d7
    float distance;

    while(1) {
        distance = measure();
        lcd.cls();
        lcd.printf("Distance = %.2f in.", distance);
        wait(0.5);
    }
}

// HCSR04 "driver"
float measure()
{
    Timer timer;
    long time;
    DigitalOut trigger(PTB9);
    DigitalIn echo(PTB8);

    timer.reset();

    // Ensure HCSR04 is idle.
    trigger = 0;
    wait (0.060);

    // Trigger the HCSR04.
    trigger = 1;
    wait_us(10);
    trigger = 0;

    // Wait for the HCSR04's measurement cycle to begin.
    while (echo == 0)
        ;

    // Start measuring.
    timer.start();
    while (echo == 1)
        ;
    timer.stop();

    time = timer.read_us();

    if (time > 30000) // Delay at maximum range plus some slop.
        return -1.0;   // Didn't receive an echo.
    else
        return 0.006756 * time;
}