File content as of revision 26:e6ad33b227c6:

/* mbed Microcontroller Library
 * Copyright (c) 2006-2013 ARM Limited
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "mbed.h"
#include "BLEDevice.h"

BLEDevice  ble;
DigitalOut led1(LED1);

#define NEED_CONSOLE_OUTPUT 0 /* Set this if you need debug messages on the console;
                               * it will have an impact on code-size and power consumption. */

#if NEED_CONSOLE_OUTPUT
Serial  pc(USBTX, USBRX);
#define DEBUG(...) { pc.printf(__VA_ARGS__); }
#else
#define DEBUG(...) /* nothing */
#endif /* #if NEED_CONSOLE_OUTPUT */

/* Device Information service */
const char         deviceName[] = { 'm', 'b', 'e', 'd' };
GattCharacteristic deviceManufacturer(GattCharacteristic::UUID_MANUFACTURER_NAME_STRING_CHAR, (uint8_t *)deviceName, sizeof(deviceName), sizeof(deviceName),
                                      GattCharacteristic::BLE_GATT_CHAR_PROPERTIES_READ);
GattCharacteristic *deviceInformationChars[] = {&deviceManufacturer};
GattService        deviceInformationService(GattService::UUID_DEVICE_INFORMATION_SERVICE, deviceInformationChars,
                                            sizeof(deviceInformationChars) / sizeof(GattCharacteristic *));

/* Heart Rate Service */
/* Service:  https://developer.bluetooth.org/gatt/services/Pages/ServiceViewer.aspx?u=org.bluetooth.service.heart_rate.xml */
/* HRM Char: https://developer.bluetooth.org/gatt/characteristics/Pages/CharacteristicViewer.aspx?u=org.bluetooth.characteristic.heart_rate_measurement.xml */
/* Location: https://developer.bluetooth.org/gatt/characteristics/Pages/CharacteristicViewer.aspx?u=org.bluetooth.characteristic.body_sensor_location.xml */
static uint8_t hrmCounter = 100;
static uint8_t bpm[2] = {0x00, hrmCounter};
GattCharacteristic hrmRate(GattCharacteristic::UUID_HEART_RATE_MEASUREMENT_CHAR, bpm, sizeof(bpm), sizeof(bpm),
                           GattCharacteristic::BLE_GATT_CHAR_PROPERTIES_NOTIFY);
static const uint8_t location = 0x03; /* Finger */
GattCharacteristic hrmLocation(GattCharacteristic::UUID_BODY_SENSOR_LOCATION_CHAR,
                               (uint8_t *)&location, sizeof(location), sizeof(location),
                               GattCharacteristic::BLE_GATT_CHAR_PROPERTIES_READ);
GattCharacteristic *hrmChars[] = {&hrmRate, &hrmLocation, };
GattService        hrmService(GattService::UUID_HEART_RATE_SERVICE, hrmChars, sizeof(hrmChars) / sizeof(GattCharacteristic *));

void disconnectionCallback(void)
{
    DEBUG("Disconnected!\n\r");
    DEBUG("Restarting the advertising process\n\r");
    ble.startAdvertising();
}

/**
 * Triggered periodically by the 'ticker' interrupt; updates hrmCounter.
 */
void periodicCallback(void)
{
    led1 = !led1; /* Do blinky on LED1 while we're waiting for BLE events */

    if (ble.getGapState().connected) {
        /* Update the HRM measurement */
        /* First byte = 8-bit values, no extra info, Second byte = uint8_t HRM value */
        /* See --> https://developer.bluetooth.org/gatt/characteristics/Pages/CharacteristicViewer.aspx?u=org.bluetooth.characteristic.heart_rate_measurement.xml */
        hrmCounter++;
        if (hrmCounter == 175) {
            hrmCounter = 100;
        }
        bpm[1] = hrmCounter;
        ble.updateCharacteristicValue(hrmRate.getHandle(), bpm, sizeof(bpm));
    }
}

int main(void)
{
    led1 = 1;
    Ticker ticker;
    ticker.attach(periodicCallback, 1);

    DEBUG("Initialising the nRF51822\n\r");
    ble.init();
    ble.onDisconnection(disconnectionCallback);

    /* setup advertising */
    ble.accumulateAdvertisingPayload(GapAdvertisingData::BREDR_NOT_SUPPORTED);
    ble.accumulateAdvertisingPayload(GapAdvertisingData::HEART_RATE_SENSOR_HEART_RATE_BELT);
    ble.setAdvertisingType(GapAdvertisingParams::ADV_CONNECTABLE_UNDIRECTED);
    ble.setAdvertisingInterval(160); /* 100ms; in multiples of 0.625ms. */
    ble.startAdvertising();

    ble.addService(deviceInformationService);
    ble.addService(hrmService);

    while (true) {
        ble.waitForEvent();
    }
}