mbed-os-examples / Mbed OS mbed-os-example-ble-Button

BLE_Button is a BLE service template. It handles a read-only characteristic with a simple input (boolean values). The input's source is the button on the board itself - the characteristic's value changes when the button is pressed or released. The canonical source for this example lives at https://github.com/ARMmbed/mbed-os-example-ble/tree/master/BLE_Button

BLE_Button is a BLE service template. It handles a read-only characteristic with a simple input (boolean values). The input's source is the button on the board itself - the characteristic's value changes when the button is pressed or released.

The template covers:

  • Setting up advertising and connection modes.
  • Creating an input characteristic: read-only, boolean, with notifications.
  • Constructing a service class and adding it to the BLE stack.
  • Assigning UUIDs to the service and its characteristic.
  • Pushing notifications when the characteristic's value changes.

Running the application

Requirements

The sample application can be seen on any BLE scanner on a smartphone. If you don't have a scanner on your phone, please install :

- nRF Master Control Panel for Android.

- LightBlue for iPhone.

Hardware requirements are in the main readme.

Building instructions

Building with mbed CLI

If you'd like to use mbed CLI to build this, then you should refer to the main readme. The instructions here relate to using the developer.mbed.org Online Compiler

In order to build this example in the mbed Online Compiler, first import the example using the ‘Import’ button on the right hand side.

Next, select a platform to build for. This must either be a platform that supports BLE, for example the NRF51-DK, or one of the following:

List of platforms supporting Bluetooth Low Energy

Or you must also add a piece of hardware and the supporting library that includes a Bluetooth Low Energy driver for that hardware, for example the K64F or NUCLEO_F401RE with the X-NUCLEO-IDB05A1

List of components supporting Bluetooth Low Energy.

Once you have selected your platform, compile the example and drag and drop the resulting binary onto your board.

For general instructions on using the mbed Online Compiler, please see the mbed Handbook

Checking for success

Note: Screens captures depicted below show what is expected from this example if the scanner used is nRF Master Control Panel version 4.0.5. If you encounter any difficulties consider trying another scanner or another version of nRF Master Control Panel. Alternative scanners may require reference to their manuals.

  • Build the application and install it on your board as explained in the building instructions.
  • Open the BLE scanner on your phone.
  • Start a scan.

https://developer.mbed.org/teams/mbed-os-examples/code/mbed-os-example-ble-Button/raw-file/3fe9d5124576/img/start_scan.png

figure 1 How to start scan using nRF Master Control Panel 4.0.5

  • Find your device; it should appear with the name `Button` in the scanner.

https://developer.mbed.org/teams/mbed-os-examples/code/mbed-os-example-ble-Button/raw-file/3fe9d5124576/img/scan_results.png

figure 2 Scan results using nRF Master Control Panel 4.0.5

  • Establish a connection with the device.

https://developer.mbed.org/teams/mbed-os-examples/code/mbed-os-example-ble-Button/raw-file/3fe9d5124576/img/connection.png

figure 3 How to establish a connection using Master Control Panel 4.0.5

  • Discover the services and the characteristics on the device. The Button service has the UUID `0xA000` and includes the Button state characteristic which has the UUID `0xA001`. Depending on your scanner, non standard 16-bit UUID's can be displayed as 128-bit UUID's. If it is the case the following format will be used: `0000XXXX-0000-1000-8000-00805F9B34FB` where `XXXX` is the hexadecimal representation of the 16-bit UUID value.

https://developer.mbed.org/teams/mbed-os-examples/code/mbed-os-example-ble-Button/raw-file/3fe9d5124576/img/discovery.png

figure 4 Representation of the Button service using Master Control Panel 4.0.5

  • Register for the notifications sent by the button state characteristic then the scanner will automatically receive a notification containing the new state of the button every time the state of the button changes.

https://developer.mbed.org/teams/mbed-os-examples/code/mbed-os-example-ble-Button/raw-file/3fe9d5124576/img/register_to_notifications.png

figure 5 How to register to notifications using Master Control Panel 4.0.5

  • Pressing Button 1 on your board updates the state of the button and sends a notification to the scanner. The new state of the button characteristic value should be equal to 0x01.

https://developer.mbed.org/teams/mbed-os-examples/code/mbed-os-example-ble-Button/raw-file/3fe9d5124576/img/button_pressed.png

figure 6 Notification of button pressed using Master Control Panel 4.0.5

  • Releasing Button 1 on your board updates the state of the button and sends a notification to the scanner. The new state of the button characteristic value should be equal to 0x00.

https://developer.mbed.org/teams/mbed-os-examples/code/mbed-os-example-ble-Button/raw-file/3fe9d5124576/img/button_depressed.png

figure 7 Notification of button depressed using Master Control Panel 4.0.5

source/main.cpp@78:f06ac76a8f6d, 2019-01-14 (annotated)

Committer:
mbed_official
Date:
Mon Jan 14 10:45:22 2019 +0000
Revision:
78:f06ac76a8f6d
Parent:
47:6aa590a64e1e
Child:
83:88f5f523e62e
Merge pull request #208 from ARMmbed/mbed-os-5.11.0-oob



Mbed OS 5.11.0

.

Commit copied from https://github.com/ARMmbed/mbed-os-example-ble

Who changed what in which revision?

UserRevisionLine numberNew contents of line
Vincent Coubard 0:3fe9d5124576 1 /* mbed Microcontroller Library
Vincent Coubard 0:3fe9d5124576 2 * Copyright (c) 2006-2013 ARM Limited
Vincent Coubard 0:3fe9d5124576 3 *
Vincent Coubard 0:3fe9d5124576 4 * Licensed under the Apache License, Version 2.0 (the "License");
Vincent Coubard 0:3fe9d5124576 5 * you may not use this file except in compliance with the License.
Vincent Coubard 0:3fe9d5124576 6 * You may obtain a copy of the License at
Vincent Coubard 0:3fe9d5124576 7 *
Vincent Coubard 0:3fe9d5124576 8 * http://www.apache.org/licenses/LICENSE-2.0
Vincent Coubard 0:3fe9d5124576 9 *
Vincent Coubard 0:3fe9d5124576 10 * Unless required by applicable law or agreed to in writing, software
Vincent Coubard 0:3fe9d5124576 11 * distributed under the License is distributed on an "AS IS" BASIS,
Vincent Coubard 0:3fe9d5124576 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
Vincent Coubard 0:3fe9d5124576 13 * See the License for the specific language governing permissions and
Vincent Coubard 0:3fe9d5124576 14 * limitations under the License.
Vincent Coubard 0:3fe9d5124576 15 */
mbed_official 14:014670ad5e18 16 #include <events/mbed_events.h>
Vincent Coubard 0:3fe9d5124576 17
Vincent Coubard 0:3fe9d5124576 18 #include <mbed.h>
Vincent Coubard 0:3fe9d5124576 19 #include "ble/BLE.h"
Vincent Coubard 0:3fe9d5124576 20 #include "ble/Gap.h"
Vincent Coubard 0:3fe9d5124576 21 #include "ButtonService.h"
mbed_official 78:f06ac76a8f6d 22 #include "pretty_printer.h"
Vincent Coubard 0:3fe9d5124576 23
mbed_official 78:f06ac76a8f6d 24 const static char DEVICE_NAME[] = "Button";
Vincent Coubard 0:3fe9d5124576 25
mbed_official 78:f06ac76a8f6d 26 static EventQueue event_queue(/* event count */ 10 * EVENTS_EVENT_SIZE);
Vincent Coubard 0:3fe9d5124576 27
Vincent Coubard 0:3fe9d5124576 28
mbed_official 78:f06ac76a8f6d 29 class BatteryDemo : ble::Gap::EventHandler {
mbed_official 78:f06ac76a8f6d 30 public:
mbed_official 78:f06ac76a8f6d 31 BatteryDemo(BLE &ble, events::EventQueue &event_queue) :
mbed_official 78:f06ac76a8f6d 32 _ble(ble),
mbed_official 78:f06ac76a8f6d 33 _event_queue(event_queue),
mbed_official 78:f06ac76a8f6d 34 _led1(LED1, 1),
mbed_official 78:f06ac76a8f6d 35 _button(BLE_BUTTON_PIN_NAME),
mbed_official 78:f06ac76a8f6d 36 _button_service(NULL),
mbed_official 78:f06ac76a8f6d 37 _button_uuid(ButtonService::BUTTON_SERVICE_UUID),
mbed_official 78:f06ac76a8f6d 38 _adv_data_builder(_adv_buffer) { }
Vincent Coubard 0:3fe9d5124576 39
mbed_official 78:f06ac76a8f6d 40 void start() {
mbed_official 78:f06ac76a8f6d 41 _ble.gap().setEventHandler(this);
Vincent Coubard 0:3fe9d5124576 42
mbed_official 78:f06ac76a8f6d 43 _ble.init(this, &BatteryDemo::on_init_complete);
Vincent Coubard 0:3fe9d5124576 44
mbed_official 78:f06ac76a8f6d 45 _event_queue.call_every(500, this, &BatteryDemo::blink);
Vincent Coubard 0:3fe9d5124576 46
mbed_official 78:f06ac76a8f6d 47 _event_queue.dispatch_forever();
mbed_official 78:f06ac76a8f6d 48 }
Vincent Coubard 0:3fe9d5124576 49
mbed_official 78:f06ac76a8f6d 50 private:
mbed_official 78:f06ac76a8f6d 51 /** Callback triggered when the ble initialization process has finished */
mbed_official 78:f06ac76a8f6d 52 void on_init_complete(BLE::InitializationCompleteCallbackContext *params) {
mbed_official 78:f06ac76a8f6d 53 if (params->error != BLE_ERROR_NONE) {
mbed_official 78:f06ac76a8f6d 54 printf("Ble initialization failed.");
mbed_official 78:f06ac76a8f6d 55 return;
mbed_official 78:f06ac76a8f6d 56 }
mbed_official 47:6aa590a64e1e 57
mbed_official 78:f06ac76a8f6d 58 print_mac_address();
mbed_official 78:f06ac76a8f6d 59
mbed_official 78:f06ac76a8f6d 60 /* Setup primary service. */
Vincent Coubard 0:3fe9d5124576 61
mbed_official 78:f06ac76a8f6d 62 _button_service = new ButtonService(_ble, false /* initial value for button pressed */);
mbed_official 78:f06ac76a8f6d 63
mbed_official 78:f06ac76a8f6d 64 _button.fall(Callback<void()>(this, &BatteryDemo::button_pressed));
mbed_official 78:f06ac76a8f6d 65 _button.rise(Callback<void()>(this, &BatteryDemo::button_released));
mbed_official 78:f06ac76a8f6d 66
mbed_official 78:f06ac76a8f6d 67 start_advertising();
Vincent Coubard 0:3fe9d5124576 68 }
Vincent Coubard 0:3fe9d5124576 69
mbed_official 78:f06ac76a8f6d 70 void start_advertising() {
mbed_official 78:f06ac76a8f6d 71 /* Create advertising parameters and payload */
mbed_official 78:f06ac76a8f6d 72
mbed_official 78:f06ac76a8f6d 73 ble::AdvertisingParameters adv_parameters(
mbed_official 78:f06ac76a8f6d 74 ble::advertising_type_t::CONNECTABLE_UNDIRECTED,
mbed_official 78:f06ac76a8f6d 75 ble::adv_interval_t(ble::millisecond_t(1000))
mbed_official 78:f06ac76a8f6d 76 );
mbed_official 78:f06ac76a8f6d 77
mbed_official 78:f06ac76a8f6d 78 uint8_t adv_buffer[ble::LEGACY_ADVERTISING_MAX_SIZE];
mbed_official 78:f06ac76a8f6d 79
mbed_official 78:f06ac76a8f6d 80 ble::AdvertisingDataBuilder adv_data_builder(adv_buffer);
mbed_official 78:f06ac76a8f6d 81
mbed_official 78:f06ac76a8f6d 82 adv_data_builder.setFlags();
mbed_official 78:f06ac76a8f6d 83 adv_data_builder.setLocalServiceList(mbed::make_Span(&_button_uuid, 1));
mbed_official 78:f06ac76a8f6d 84 adv_data_builder.setName(DEVICE_NAME);
mbed_official 78:f06ac76a8f6d 85
mbed_official 78:f06ac76a8f6d 86 /* Setup advertising */
mbed_official 78:f06ac76a8f6d 87
mbed_official 78:f06ac76a8f6d 88 ble_error_t error = _ble.gap().setAdvertisingParameters(
mbed_official 78:f06ac76a8f6d 89 ble::LEGACY_ADVERTISING_HANDLE,
mbed_official 78:f06ac76a8f6d 90 adv_parameters
mbed_official 78:f06ac76a8f6d 91 );
mbed_official 78:f06ac76a8f6d 92
mbed_official 78:f06ac76a8f6d 93 if (error) {
mbed_official 78:f06ac76a8f6d 94 print_error(error, "_ble.gap().setAdvertisingParameters() failed");
mbed_official 78:f06ac76a8f6d 95 return;
mbed_official 78:f06ac76a8f6d 96 }
mbed_official 78:f06ac76a8f6d 97
mbed_official 78:f06ac76a8f6d 98 error = _ble.gap().setAdvertisingPayload(
mbed_official 78:f06ac76a8f6d 99 ble::LEGACY_ADVERTISING_HANDLE,
mbed_official 78:f06ac76a8f6d 100 _adv_data_builder.getAdvertisingData()
mbed_official 78:f06ac76a8f6d 101 );
mbed_official 78:f06ac76a8f6d 102
mbed_official 78:f06ac76a8f6d 103 if (error) {
mbed_official 78:f06ac76a8f6d 104 print_error(error, "_ble.gap().setAdvertisingPayload() failed");
mbed_official 78:f06ac76a8f6d 105 return;
mbed_official 78:f06ac76a8f6d 106 }
mbed_official 78:f06ac76a8f6d 107
mbed_official 78:f06ac76a8f6d 108 /* Start advertising */
mbed_official 78:f06ac76a8f6d 109
mbed_official 78:f06ac76a8f6d 110 error = _ble.gap().startAdvertising(ble::LEGACY_ADVERTISING_HANDLE);
mbed_official 78:f06ac76a8f6d 111
mbed_official 78:f06ac76a8f6d 112 if (error) {
mbed_official 78:f06ac76a8f6d 113 print_error(error, "_ble.gap().startAdvertising() failed");
mbed_official 78:f06ac76a8f6d 114 return;
mbed_official 78:f06ac76a8f6d 115 }
Vincent Coubard 0:3fe9d5124576 116 }
Vincent Coubard 0:3fe9d5124576 117
mbed_official 78:f06ac76a8f6d 118 void button_pressed(void) {
mbed_official 78:f06ac76a8f6d 119 _event_queue.call(Callback<void(bool)>(_button_service, &ButtonService::updateButtonState), true);
mbed_official 78:f06ac76a8f6d 120 }
Vincent Coubard 0:3fe9d5124576 121
mbed_official 78:f06ac76a8f6d 122 void button_released(void) {
mbed_official 78:f06ac76a8f6d 123 _event_queue.call(Callback<void(bool)>(_button_service, &ButtonService::updateButtonState), false);
mbed_official 78:f06ac76a8f6d 124 }
Vincent Coubard 0:3fe9d5124576 125
mbed_official 78:f06ac76a8f6d 126 void blink(void) {
mbed_official 78:f06ac76a8f6d 127 _led1 = !_led1;
mbed_official 78:f06ac76a8f6d 128 }
mbed_official 78:f06ac76a8f6d 129
mbed_official 78:f06ac76a8f6d 130 private:
mbed_official 78:f06ac76a8f6d 131 /* Event handler */
Vincent Coubard 0:3fe9d5124576 132
mbed_official 78:f06ac76a8f6d 133 virtual void onDisconnectionComplete(const ble::DisconnectionCompleteEvent&) {
mbed_official 78:f06ac76a8f6d 134 _ble.gap().startAdvertising(ble::LEGACY_ADVERTISING_HANDLE);
mbed_official 78:f06ac76a8f6d 135 }
mbed_official 78:f06ac76a8f6d 136
mbed_official 78:f06ac76a8f6d 137 private:
mbed_official 78:f06ac76a8f6d 138 BLE &_ble;
mbed_official 78:f06ac76a8f6d 139 events::EventQueue &_event_queue;
mbed_official 47:6aa590a64e1e 140
mbed_official 78:f06ac76a8f6d 141 DigitalOut _led1;
mbed_official 78:f06ac76a8f6d 142 InterruptIn _button;
mbed_official 78:f06ac76a8f6d 143 ButtonService *_button_service;
mbed_official 78:f06ac76a8f6d 144
mbed_official 78:f06ac76a8f6d 145 UUID _button_uuid;
Vincent Coubard 0:3fe9d5124576 146
mbed_official 78:f06ac76a8f6d 147 uint8_t _adv_buffer[ble::LEGACY_ADVERTISING_MAX_SIZE];
mbed_official 78:f06ac76a8f6d 148 ble::AdvertisingDataBuilder _adv_data_builder;
mbed_official 78:f06ac76a8f6d 149 };
mbed_official 78:f06ac76a8f6d 150
mbed_official 78:f06ac76a8f6d 151 /** Schedule processing of events from the BLE middleware in the event queue. */
mbed_official 78:f06ac76a8f6d 152 void schedule_ble_events(BLE::OnEventsToProcessCallbackContext *context) {
mbed_official 78:f06ac76a8f6d 153 event_queue.call(Callback<void()>(&context->ble, &BLE::processEvents));
Vincent Coubard 0:3fe9d5124576 154 }
Vincent Coubard 0:3fe9d5124576 155
Vincent Coubard 0:3fe9d5124576 156 int main()
Vincent Coubard 0:3fe9d5124576 157 {
mbed_official 78:f06ac76a8f6d 158 BLE &ble = BLE::Instance();
mbed_official 78:f06ac76a8f6d 159 ble.onEventsToProcess(schedule_ble_events);
Vincent Coubard 0:3fe9d5124576 160
mbed_official 78:f06ac76a8f6d 161 BatteryDemo demo(ble, event_queue);
mbed_official 78:f06ac76a8f6d 162 demo.start();
Vincent Coubard 0:3fe9d5124576 163
Vincent Coubard 0:3fe9d5124576 164 return 0;
Vincent Coubard 0:3fe9d5124576 165 }
mbed_official 78:f06ac76a8f6d 166