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

This application shows how to use GAP to transmit a simple value to disconnected peer listening for advertisement every time that a value is updated. The canonical source for this example lives at: https://github.com/ARMmbed/mbed-os-example-ble/tree/master/BLE_GAPButton

Button count over GAP

This application shows how to use GAP to transmit a simple value to disconnected peer listening for advertisement every time that a value is updated:

  • The value is a count of how many times a button on the device was pressed (the code actually monitors the button's releases, not press downs).
  • We transmit the value in the SERVICE_DATA field of the advertising payload.

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-GAPButton/raw-file/8f898b781de2/img/start_scan.png

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

  • Find your device; it should be named `GAPButton`; and look at the advertisement broadcasted by your device (there is no need to connect to your device).

https://developer.mbed.org/teams/mbed-os-examples/code/mbed-os-example-ble-GAPButton/raw-file/8f898b781de2/img/discovery.png

figure 2 Scan results using nRF Master Control Panel 4.0.5.

  • The Service Data field of the advertisement packet broadcasted by your device reflects the button press count. The starting value is 0.

https://developer.mbed.org/teams/mbed-os-examples/code/mbed-os-example-ble-GAPButton/raw-file/8f898b781de2/img/initial_state.png

figure 3 Initial state of the button using nRF Master Control Panel 4.0.5.

  • Press the button on the device.

https://developer.mbed.org/teams/mbed-os-examples/code/mbed-os-example-ble-GAPButton/raw-file/8f898b781de2/img/first_press.png

figure 3 State after 1 button press using nRF Master Control Panel 4.0.5.

  • The Service Data field value of the advertisement packet should change every time you press the button.

https://developer.mbed.org/teams/mbed-os-examples/code/mbed-os-example-ble-GAPButton/raw-file/8f898b781de2/img/result.png

figure 3 State after 6 button press using nRF Master Control Panel 4.0.5.

Note

Since broadcasting is not reliable and your phone may scan intermittently, it is possible that your phone will miss button updates.

source/main.cpp@2:e532bbe3fd8e, 2016-07-28 (annotated)

Committer:
Vincent Coubard
Date:
Thu Jul 28 23:20:45 2016 +0100
Revision:
2:e532bbe3fd8e
Parent:
1:7f4e41bacb3c
Child:
3:f0ed4199b362
Sync with mbed-os-5.1.0-rc3

Who changed what in which revision?

UserRevisionLine numberNew contents of line
Vincent Coubard 2:e532bbe3fd8e 1 /* mbed Microcontroller Library
Vincent Coubard 2:e532bbe3fd8e 2 * Copyright (c) 2006-2013 ARM Limited
Vincent Coubard 2:e532bbe3fd8e 3 *
Vincent Coubard 2:e532bbe3fd8e 4 * Licensed under the Apache License, Version 2.0 (the "License");
Vincent Coubard 2:e532bbe3fd8e 5 * you may not use this file except in compliance with the License.
Vincent Coubard 2:e532bbe3fd8e 6 * You may obtain a copy of the License at
Vincent Coubard 2:e532bbe3fd8e 7 *
Vincent Coubard 2:e532bbe3fd8e 8 * http://www.apache.org/licenses/LICENSE-2.0
Vincent Coubard 2:e532bbe3fd8e 9 *
Vincent Coubard 2:e532bbe3fd8e 10 * Unless required by applicable law or agreed to in writing, software
Vincent Coubard 2:e532bbe3fd8e 11 * distributed under the License is distributed on an "AS IS" BASIS,
Vincent Coubard 2:e532bbe3fd8e 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
Vincent Coubard 2:e532bbe3fd8e 13 * See the License for the specific language governing permissions and
Vincent Coubard 2:e532bbe3fd8e 14 * limitations under the License.
Vincent Coubard 2:e532bbe3fd8e 15 */
Vincent Coubard 2:e532bbe3fd8e 16
Vincent Coubard 2:e532bbe3fd8e 17 #include <mbed-events/events.h>
Vincent Coubard 2:e532bbe3fd8e 18 #include <mbed.h>
Vincent Coubard 2:e532bbe3fd8e 19 #include "ble/BLE.h"
Vincent Coubard 2:e532bbe3fd8e 20
Vincent Coubard 2:e532bbe3fd8e 21 DigitalOut led1(LED1, 1);
Vincent Coubard 2:e532bbe3fd8e 22 InterruptIn button(BUTTON1);
Vincent Coubard 2:e532bbe3fd8e 23 uint8_t cnt;
Vincent Coubard 2:e532bbe3fd8e 24
Vincent Coubard 2:e532bbe3fd8e 25 // Change your device name below
Vincent Coubard 2:e532bbe3fd8e 26 const char DEVICE_NAME[] = "GAPButton";
Vincent Coubard 2:e532bbe3fd8e 27
Vincent Coubard 2:e532bbe3fd8e 28 /* We can arbiturarily choose the GAPButton service UUID to be 0xAA00
Vincent Coubard 2:e532bbe3fd8e 29 * as long as it does not overlap with the UUIDs defined here:
Vincent Coubard 2:e532bbe3fd8e 30 * https://developer.bluetooth.org/gatt/services/Pages/ServicesHome.aspx */
Vincent Coubard 2:e532bbe3fd8e 31 #define GAPButtonUUID 0xAA00
Vincent Coubard 2:e532bbe3fd8e 32 const uint16_t uuid16_list[] = {GAPButtonUUID};
Vincent Coubard 2:e532bbe3fd8e 33
Vincent Coubard 2:e532bbe3fd8e 34 static EventQueue eventQueue(
Vincent Coubard 2:e532bbe3fd8e 35 /* event count */ 16 * /* event size */ 32
Vincent Coubard 2:e532bbe3fd8e 36 );
Vincent Coubard 2:e532bbe3fd8e 37
Vincent Coubard 2:e532bbe3fd8e 38 void print_error(ble_error_t error, const char* msg)
Vincent Coubard 2:e532bbe3fd8e 39 {
Vincent Coubard 2:e532bbe3fd8e 40 printf("%s: ", msg);
Vincent Coubard 2:e532bbe3fd8e 41 switch(error) {
Vincent Coubard 2:e532bbe3fd8e 42 case BLE_ERROR_NONE:
Vincent Coubard 2:e532bbe3fd8e 43 printf("BLE_ERROR_NONE: No error");
Vincent Coubard 2:e532bbe3fd8e 44 break;
Vincent Coubard 2:e532bbe3fd8e 45 case BLE_ERROR_BUFFER_OVERFLOW:
Vincent Coubard 2:e532bbe3fd8e 46 printf("BLE_ERROR_BUFFER_OVERFLOW: The requested action would cause a buffer overflow and has been aborted");
Vincent Coubard 2:e532bbe3fd8e 47 break;
Vincent Coubard 2:e532bbe3fd8e 48 case BLE_ERROR_NOT_IMPLEMENTED:
Vincent Coubard 2:e532bbe3fd8e 49 printf("BLE_ERROR_NOT_IMPLEMENTED: Requested a feature that isn't yet implement or isn't supported by the target HW");
Vincent Coubard 2:e532bbe3fd8e 50 break;
Vincent Coubard 2:e532bbe3fd8e 51 case BLE_ERROR_PARAM_OUT_OF_RANGE:
Vincent Coubard 2:e532bbe3fd8e 52 printf("BLE_ERROR_PARAM_OUT_OF_RANGE: One of the supplied parameters is outside the valid range");
Vincent Coubard 2:e532bbe3fd8e 53 break;
Vincent Coubard 2:e532bbe3fd8e 54 case BLE_ERROR_INVALID_PARAM:
Vincent Coubard 2:e532bbe3fd8e 55 printf("BLE_ERROR_INVALID_PARAM: One of the supplied parameters is invalid");
Vincent Coubard 2:e532bbe3fd8e 56 break;
Vincent Coubard 2:e532bbe3fd8e 57 case BLE_STACK_BUSY:
Vincent Coubard 2:e532bbe3fd8e 58 printf("BLE_STACK_BUSY: The stack is busy");
Vincent Coubard 2:e532bbe3fd8e 59 break;
Vincent Coubard 2:e532bbe3fd8e 60 case BLE_ERROR_INVALID_STATE:
Vincent Coubard 2:e532bbe3fd8e 61 printf("BLE_ERROR_INVALID_STATE: Invalid state");
Vincent Coubard 2:e532bbe3fd8e 62 break;
Vincent Coubard 2:e532bbe3fd8e 63 case BLE_ERROR_NO_MEM:
Vincent Coubard 2:e532bbe3fd8e 64 printf("BLE_ERROR_NO_MEM: Out of Memory");
Vincent Coubard 2:e532bbe3fd8e 65 break;
Vincent Coubard 2:e532bbe3fd8e 66 case BLE_ERROR_OPERATION_NOT_PERMITTED:
Vincent Coubard 2:e532bbe3fd8e 67 printf("BLE_ERROR_OPERATION_NOT_PERMITTED");
Vincent Coubard 2:e532bbe3fd8e 68 break;
Vincent Coubard 2:e532bbe3fd8e 69 case BLE_ERROR_INITIALIZATION_INCOMPLETE:
Vincent Coubard 2:e532bbe3fd8e 70 printf("BLE_ERROR_INITIALIZATION_INCOMPLETE");
Vincent Coubard 2:e532bbe3fd8e 71 break;
Vincent Coubard 2:e532bbe3fd8e 72 case BLE_ERROR_ALREADY_INITIALIZED:
Vincent Coubard 2:e532bbe3fd8e 73 printf("BLE_ERROR_ALREADY_INITIALIZED");
Vincent Coubard 2:e532bbe3fd8e 74 break;
Vincent Coubard 2:e532bbe3fd8e 75 case BLE_ERROR_UNSPECIFIED:
Vincent Coubard 2:e532bbe3fd8e 76 printf("BLE_ERROR_UNSPECIFIED: Unknown error");
Vincent Coubard 2:e532bbe3fd8e 77 break;
Vincent Coubard 2:e532bbe3fd8e 78 case BLE_ERROR_INTERNAL_STACK_FAILURE:
Vincent Coubard 2:e532bbe3fd8e 79 printf("BLE_ERROR_INTERNAL_STACK_FAILURE: internal stack faillure");
Vincent Coubard 2:e532bbe3fd8e 80 break;
Vincent Coubard 2:e532bbe3fd8e 81 }
Vincent Coubard 2:e532bbe3fd8e 82 printf("\r\n");
Vincent Coubard 2:e532bbe3fd8e 83 }
Vincent Coubard 2:e532bbe3fd8e 84
Vincent Coubard 2:e532bbe3fd8e 85 void updatePayload(void)
Vincent Coubard 2:e532bbe3fd8e 86 {
Vincent Coubard 2:e532bbe3fd8e 87 // Update the count in the SERVICE_DATA field of the advertising payload
Vincent Coubard 2:e532bbe3fd8e 88 uint8_t service_data[3];
Vincent Coubard 2:e532bbe3fd8e 89 service_data[0] = GAPButtonUUID & 0xff;
Vincent Coubard 2:e532bbe3fd8e 90 service_data[1] = GAPButtonUUID >> 8;
Vincent Coubard 2:e532bbe3fd8e 91 service_data[2] = cnt; // Put the button click count in the third byte
Vincent Coubard 2:e532bbe3fd8e 92 ble_error_t err = BLE::Instance().gap().updateAdvertisingPayload(GapAdvertisingData::SERVICE_DATA, (uint8_t *)service_data, sizeof(service_data));
Vincent Coubard 2:e532bbe3fd8e 93 if (err != BLE_ERROR_NONE) {
Vincent Coubard 2:e532bbe3fd8e 94 print_error(err, "Updating payload failed");
Vincent Coubard 2:e532bbe3fd8e 95 }
Vincent Coubard 2:e532bbe3fd8e 96 }
Vincent Coubard 2:e532bbe3fd8e 97
Vincent Coubard 2:e532bbe3fd8e 98 void buttonPressedCallback(void)
Vincent Coubard 2:e532bbe3fd8e 99 {
Vincent Coubard 2:e532bbe3fd8e 100 ++cnt;
Vincent Coubard 2:e532bbe3fd8e 101
Vincent Coubard 2:e532bbe3fd8e 102 // Calling BLE api in interrupt context may cause race conditions
Vincent Coubard 2:e532bbe3fd8e 103 // Using mbed-events to schedule calls to BLE api for safety
Vincent Coubard 2:e532bbe3fd8e 104 eventQueue.post(updatePayload);
Vincent Coubard 2:e532bbe3fd8e 105 }
Vincent Coubard 2:e532bbe3fd8e 106
Vincent Coubard 2:e532bbe3fd8e 107 void blinkCallback(void)
Vincent Coubard 2:e532bbe3fd8e 108 {
Vincent Coubard 2:e532bbe3fd8e 109 led1 = !led1;
Vincent Coubard 2:e532bbe3fd8e 110 }
Vincent Coubard 2:e532bbe3fd8e 111
Vincent Coubard 2:e532bbe3fd8e 112 void bleInitComplete(BLE::InitializationCompleteCallbackContext *context)
Vincent Coubard 2:e532bbe3fd8e 113 {
Vincent Coubard 2:e532bbe3fd8e 114 BLE& ble = context->ble;
Vincent Coubard 2:e532bbe3fd8e 115 ble_error_t err = context->error;
Vincent Coubard 2:e532bbe3fd8e 116
Vincent Coubard 2:e532bbe3fd8e 117 if (err != BLE_ERROR_NONE) {
Vincent Coubard 2:e532bbe3fd8e 118 print_error(err, "BLE initialisation failed");
Vincent Coubard 2:e532bbe3fd8e 119 return;
Vincent Coubard 2:e532bbe3fd8e 120 }
Vincent Coubard 2:e532bbe3fd8e 121
Vincent Coubard 2:e532bbe3fd8e 122 // Set up the advertising flags. Note: not all combination of flags are valid
Vincent Coubard 2:e532bbe3fd8e 123 // BREDR_NOT_SUPPORTED: Device does not support Basic Rate or Enchanced Data Rate, It is Low Energy only.
Vincent Coubard 2:e532bbe3fd8e 124 // LE_GENERAL_DISCOVERABLE: Peripheral device is discoverable at any moment
Vincent Coubard 2:e532bbe3fd8e 125 err = ble.gap().accumulateAdvertisingPayload(GapAdvertisingData::BREDR_NOT_SUPPORTED | GapAdvertisingData::LE_GENERAL_DISCOVERABLE);
Vincent Coubard 2:e532bbe3fd8e 126 if (err != BLE_ERROR_NONE) {
Vincent Coubard 2:e532bbe3fd8e 127 print_error(err, "Setting GAP flags failed");
Vincent Coubard 2:e532bbe3fd8e 128 return;
Vincent Coubard 2:e532bbe3fd8e 129 }
Vincent Coubard 2:e532bbe3fd8e 130
Vincent Coubard 2:e532bbe3fd8e 131 // Put the device name in the advertising payload
Vincent Coubard 2:e532bbe3fd8e 132 err = ble.gap().accumulateAdvertisingPayload(GapAdvertisingData::COMPLETE_LOCAL_NAME, (uint8_t *)DEVICE_NAME, sizeof(DEVICE_NAME));
Vincent Coubard 2:e532bbe3fd8e 133 if (err != BLE_ERROR_NONE) {
Vincent Coubard 2:e532bbe3fd8e 134 print_error(err, "Setting device name failed");
Vincent Coubard 2:e532bbe3fd8e 135 return;
Vincent Coubard 2:e532bbe3fd8e 136 }
Vincent Coubard 2:e532bbe3fd8e 137
Vincent Coubard 2:e532bbe3fd8e 138 err = ble.gap().accumulateAdvertisingPayload(GapAdvertisingData::COMPLETE_LIST_16BIT_SERVICE_IDS, (uint8_t *)uuid16_list, sizeof(uuid16_list));
Vincent Coubard 2:e532bbe3fd8e 139 if (err != BLE_ERROR_NONE) {
Vincent Coubard 2:e532bbe3fd8e 140 print_error(err, "Setting service UUID failed");
Vincent Coubard 2:e532bbe3fd8e 141 return;
Vincent Coubard 2:e532bbe3fd8e 142 }
Vincent Coubard 2:e532bbe3fd8e 143
Vincent Coubard 2:e532bbe3fd8e 144 // The Service Data data type consists of a service UUID with the data associated with that service.
Vincent Coubard 2:e532bbe3fd8e 145 // We will encode the number of button clicks in the Service Data field
Vincent Coubard 2:e532bbe3fd8e 146 // First two bytes of SERVICE_DATA field should contain the UUID of the service
Vincent Coubard 2:e532bbe3fd8e 147 uint8_t service_data[3];
Vincent Coubard 2:e532bbe3fd8e 148 service_data[0] = GAPButtonUUID & 0xff;
Vincent Coubard 2:e532bbe3fd8e 149 service_data[1] = GAPButtonUUID >> 8;
Vincent Coubard 2:e532bbe3fd8e 150 service_data[2] = cnt; // Put the button click count in the third byte
Vincent Coubard 2:e532bbe3fd8e 151 err = ble.gap().accumulateAdvertisingPayload(GapAdvertisingData::SERVICE_DATA, (uint8_t *)service_data, sizeof(service_data));
Vincent Coubard 2:e532bbe3fd8e 152 if (err != BLE_ERROR_NONE) {
Vincent Coubard 2:e532bbe3fd8e 153 print_error(err, "Setting service data failed");
Vincent Coubard 2:e532bbe3fd8e 154 return;
Vincent Coubard 2:e532bbe3fd8e 155 }
Vincent Coubard 2:e532bbe3fd8e 156
Vincent Coubard 2:e532bbe3fd8e 157 // It is not connectable as we are just boardcasting
Vincent Coubard 2:e532bbe3fd8e 158 ble.gap().setAdvertisingType(GapAdvertisingParams::ADV_NON_CONNECTABLE_UNDIRECTED);
Vincent Coubard 2:e532bbe3fd8e 159
Vincent Coubard 2:e532bbe3fd8e 160 // Send out the advertising payload every 1000ms
Vincent Coubard 2:e532bbe3fd8e 161 ble.gap().setAdvertisingInterval(1000);
Vincent Coubard 2:e532bbe3fd8e 162
Vincent Coubard 2:e532bbe3fd8e 163 err = ble.gap().startAdvertising();
Vincent Coubard 2:e532bbe3fd8e 164 if (err != BLE_ERROR_NONE) {
Vincent Coubard 2:e532bbe3fd8e 165 print_error(err, "Sart advertising failed");
Vincent Coubard 2:e532bbe3fd8e 166 return;
Vincent Coubard 2:e532bbe3fd8e 167 }
Vincent Coubard 2:e532bbe3fd8e 168 }
Vincent Coubard 2:e532bbe3fd8e 169
Vincent Coubard 2:e532bbe3fd8e 170 void scheduleBleEventsProcessing(BLE::OnEventsToProcessCallbackContext* context) {
Vincent Coubard 2:e532bbe3fd8e 171 BLE &ble = BLE::Instance();
Vincent Coubard 2:e532bbe3fd8e 172 eventQueue.post(Callback<void()>(&ble, &BLE::processEvents));
Vincent Coubard 2:e532bbe3fd8e 173 }
Vincent Coubard 2:e532bbe3fd8e 174
Vincent Coubard 2:e532bbe3fd8e 175 int main()
Vincent Coubard 2:e532bbe3fd8e 176 {
Vincent Coubard 2:e532bbe3fd8e 177 cnt = 0;
Vincent Coubard 2:e532bbe3fd8e 178
Vincent Coubard 2:e532bbe3fd8e 179 BLE &ble = BLE::Instance();
Vincent Coubard 2:e532bbe3fd8e 180 ble.onEventsToProcess(scheduleBleEventsProcessing);
Vincent Coubard 2:e532bbe3fd8e 181 ble_error_t err = ble.init(bleInitComplete);
Vincent Coubard 2:e532bbe3fd8e 182 if (err != BLE_ERROR_NONE) {
Vincent Coubard 2:e532bbe3fd8e 183 print_error(err, "BLE initialisation failed");
Vincent Coubard 2:e532bbe3fd8e 184 return 0;
Vincent Coubard 2:e532bbe3fd8e 185 }
Vincent Coubard 2:e532bbe3fd8e 186
Vincent Coubard 2:e532bbe3fd8e 187 // Blink LED every 500 ms to indicate system aliveness
Vincent Coubard 2:e532bbe3fd8e 188 eventQueue.post_every(500, blinkCallback);
Vincent Coubard 2:e532bbe3fd8e 189
Vincent Coubard 2:e532bbe3fd8e 190 // Register function to be called when button is released
Vincent Coubard 2:e532bbe3fd8e 191 button.rise(buttonPressedCallback);
Vincent Coubard 2:e532bbe3fd8e 192
Vincent Coubard 2:e532bbe3fd8e 193 while (true) {
Vincent Coubard 2:e532bbe3fd8e 194 eventQueue.dispatch();
Vincent Coubard 2:e532bbe3fd8e 195 }
Vincent Coubard 2:e532bbe3fd8e 196
Vincent Coubard 2:e532bbe3fd8e 197 return 0;
Vincent Coubard 2:e532bbe3fd8e 198 }