This example creates and updates a standard Battery Level service containing a single GATT characteristic. The battery service transmits a device's battery level in percentage, with 100% being a fully charged battery and 0% being a fully drained battery. The canonical source for this example lives at https://github.com/ARMmbed/mbed-os-example-ble/tree/master/BLE_BatteryLevel

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main.cpp

00001 /* mbed Microcontroller Library
00002  * Copyright (c) 2006-2014 ARM Limited
00003  *
00004  * Licensed under the Apache License, Version 2.0 (the "License");
00005  * you may not use this file except in compliance with the License.
00006  * You may obtain a copy of the License at
00007  *
00008  *     http://www.apache.org/licenses/LICENSE-2.0
00009  *
00010  * Unless required by applicable law or agreed to in writing, software
00011  * distributed under the License is distributed on an "AS IS" BASIS,
00012  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00013  * See the License for the specific language governing permissions and
00014  * limitations under the License.
00015  */
00016 
00017 #include <events/mbed_events.h>
00018 #include <mbed.h>
00019 #include "ble/BLE.h"
00020 #include "ble/Gap.h"
00021 #include "ble/services/BatteryService.h"
00022 #include "pretty_printer.h"
00023 
00024 static DigitalOut led1(LED1, 1);
00025 
00026 const static char DEVICE_NAME[] = "BATTERY";
00027 
00028 static events::EventQueue event_queue(/* event count */ 16 * EVENTS_EVENT_SIZE);
00029 
00030 class BatteryDemo : ble::Gap::EventHandler {
00031 public:
00032     BatteryDemo(BLE &ble, events::EventQueue &event_queue) :
00033         _ble(ble),
00034         _event_queue(event_queue),
00035         _battery_uuid(GattService::UUID_BATTERY_SERVICE),
00036         _battery_level(50),
00037         _battery_service(ble, _battery_level),
00038         _adv_data_builder(_adv_buffer) { }
00039 
00040     void start() {
00041         _ble.gap().setEventHandler(this);
00042 
00043         _ble.init(this, &BatteryDemo::on_init_complete);
00044 
00045         _event_queue.call_every(500, this, &BatteryDemo::blink);
00046         _event_queue.call_every(1000, this, &BatteryDemo::update_sensor_value);
00047 
00048         _event_queue.dispatch_forever();
00049     }
00050 
00051 private:
00052     /** Callback triggered when the ble initialization process has finished */
00053     void on_init_complete(BLE::InitializationCompleteCallbackContext *params) {
00054         if (params->error != BLE_ERROR_NONE) {
00055             print_error(params->error, "Ble initialization failed.");
00056             return;
00057         }
00058 
00059         print_mac_address();
00060 
00061         start_advertising();
00062     }
00063 
00064     void start_advertising() {
00065         /* Create advertising parameters and payload */
00066 
00067         ble::AdvertisingParameters adv_parameters(
00068             ble::advertising_type_t::CONNECTABLE_UNDIRECTED,
00069             ble::adv_interval_t(ble::millisecond_t(1000))
00070         );
00071 
00072         _adv_data_builder.setFlags();
00073         _adv_data_builder.setLocalServiceList(mbed::make_Span(&_battery_uuid, 1));
00074         _adv_data_builder.setName(DEVICE_NAME);
00075 
00076         /* Setup advertising */
00077 
00078         ble_error_t error = _ble.gap().setAdvertisingParameters(
00079             ble::LEGACY_ADVERTISING_HANDLE,
00080             adv_parameters
00081         );
00082 
00083         if (error) {
00084             print_error(error, "_ble.gap().setAdvertisingParameters() failed");
00085             return;
00086         }
00087 
00088         error = _ble.gap().setAdvertisingPayload(
00089             ble::LEGACY_ADVERTISING_HANDLE,
00090             _adv_data_builder.getAdvertisingData()
00091         );
00092 
00093         if (error) {
00094             print_error(error, "_ble.gap().setAdvertisingPayload() failed");
00095             return;
00096         }
00097 
00098         /* Start advertising */
00099 
00100         error = _ble.gap().startAdvertising(ble::LEGACY_ADVERTISING_HANDLE);
00101 
00102         if (error) {
00103             print_error(error, "_ble.gap().startAdvertising() failed");
00104             return;
00105         }
00106     }
00107 
00108     void update_sensor_value() {
00109         if (_ble.gap().getState().connected) {
00110             _battery_level++;
00111             if (_battery_level > 100) {
00112                 _battery_level = 20;
00113             }
00114 
00115             _battery_service.updateBatteryLevel(_battery_level);
00116         }
00117     }
00118 
00119     void blink(void) {
00120         led1 = !led1;
00121     }
00122 
00123 private:
00124     /* Event handler */
00125 
00126     void onDisconnectionComplete(const ble::DisconnectionCompleteEvent&) {
00127         _ble.gap().startAdvertising(ble::LEGACY_ADVERTISING_HANDLE);
00128     }
00129 
00130 private:
00131     BLE &_ble;
00132     events::EventQueue &_event_queue;
00133 
00134     UUID _battery_uuid;
00135 
00136     uint8_t _battery_level;
00137     BatteryService _battery_service;
00138 
00139     uint8_t _adv_buffer[ble::LEGACY_ADVERTISING_MAX_SIZE];
00140     ble::AdvertisingDataBuilder _adv_data_builder;
00141 };
00142 
00143 /** Schedule processing of events from the BLE middleware in the event queue. */
00144 void schedule_ble_events(BLE::OnEventsToProcessCallbackContext *context) {
00145     event_queue.call(Callback<void()>(&context->ble, &BLE::processEvents));
00146 }
00147 
00148 int main()
00149 {
00150     BLE &ble = BLE::Instance();
00151     ble.onEventsToProcess(schedule_ble_events);
00152 
00153     BatteryDemo demo(ble, event_queue);
00154     demo.start();
00155 
00156     return 0;
00157 }