File content as of revision 3:e9646631084f:

// Headers necessary for mbed and BLE device mode
#include "mbed.h"
#include "BLEDevice.h"

// BLE object
BLEDevice ble;

/**
  You have up to 26 bytes of advertising data to use.
  Make up your own encoding for these 26bytes, send it across
  and decode it using the evothings app.
 */
const static uint8_t AdvData[] = {"ChangeThisData"};             // example of character data
//const static uint8_t AdvData[] = {0x01,0x02,0x03,0x04,0x05};   // example of hex data

// main program
int main(void)
{
    // Initialize BLE baselayer, always do this first!
    ble.init();

    // Sacrifice 3B of 31B to Advertising Flags
    ble.accumulateAdvertisingPayload(GapAdvertisingData::BREDR_NOT_SUPPORTED | GapAdvertisingData::LE_GENERAL_DISCOVERABLE );
    ble.setAdvertisingType(GapAdvertisingParams::ADV_NON_CONNECTABLE_UNDIRECTED);

    // Sacrifice 2B of 31B to AdvType overhead, rest goes to AdvData array you define
    ble.accumulateAdvertisingPayload(GapAdvertisingData::MANUFACTURER_SPECIFIC_DATA, AdvData, sizeof(AdvData));

    // Set advertising interval. Longer interval = longer battery life
    ble.setAdvertisingInterval(160); // 100ms; in multiples of 0.625ms.
    ble.startAdvertising();

    // Infinite loop waiting for BLE events
    for (;;) {
        ble.waitForEvent(); // this saves battery
    }
}