File content as of revision 2:39ba9beabf3c:

// I2CU - Search for devices on an I2C bus
// Copyright (c) 2009, sford
// Released under the MIT License: http://mbed.org/license/mit
//
// Goes through each device address, seeing if it gets a response
//  - for every device if finds, it prints the 8-bit address
//  - if the program hangs, the bus isn't working (check pull-ups etc)
//  - if it doesn't find your device, check power/bus wiring etc

#include "mbed.h"

I2C i2c(I2C_SDA, I2C_SCL); // sda, scl
Ticker repeatTicker;

void repeat()
{
    printf("I2CU! Searching for I2C devices...\n");

    int count = 0;
    for (int address=0; address<256; address+=2) {
        bool temp = i2c.write(address, NULL, 0); // 0 if successful, otherwise non-zero
        if (!temp && (address >> 1) != 0) { // not interested in address 0
            printf(" - I2C device found at address 0x%02X\n", address >> 1);
            count++;
        }
    }
    printf("%d device(s) found\n", count);
}

int main()
{
    repeatTicker.attach(&repeat, 2.0);
}