3.1.1.3 BLE Scanning Extended Advertisements

Introduction

This section describes in detail the scanning of Extended Advertisements (ADV_EXT_IND, ADV_AUX_IND) on the WBZ451 Curiosity board. For a successful scan of Extended Advertisement user needs to have a broadcaster transmitting these Advertisements. In BLE, a central or observer always starts with scanning.

Using the “scan_ext_adv” application example in combination with “ext_adv” example will enable users to test features like long range (Coded PHY) and sending data (1M, 2M, Coded PHY) over extended advertisements

Users can choose to run the precompiled application example .hex file on the WBZ451 Curiosity Board and experience the demo or go through the steps involved in developing this application from scratch

Recommendation is to follow the examples in order, by learning the basic concepts first and then progressing to the more advanced topics.

Recommended Reading

1. BLE Software Specification
2. FreeRtos BLE App Initialize
3. Adding UART

Hardware Requirement

SDK Setup

• Getting Started with Software Development

Software Requirement

• Tera Term

Smart phone App

None

Programming the Precompiled .hex File or Application Example

Programming the .hex File using MPLAB X IPE

1. Central Device – Precompiled .hex file is located in "<Harmony Content Path>\wireless_apps_pic32cxbz2_wbz45\apps\ble\building_blocks\central\scan_ext_adv\hex" folder
2. Peripheral Device – Precompiled .hex file is located in "<Harmony Content Path>\wireless_apps_pic32cxbz2_wbz45\apps\ble\building_blocks\peripheral\ext_adv\hex" folder
3. For more details on the steps, go to Programming a Device
   Note: Users must choose the correct device and tool information

1. Follow steps mentioned in the Running a Precompiled Example document
2. Central Device – Open and program the Application Example scan_ext_adv.X located in "<Harmony Content Path>\wireless_apps_pic32cxbz2_wbz45\apps\ble\building_blocks\central\scan_ext_adv\firmware" using MPLAB X IDE
3. Peripheral Device – Open and program the Application Example ext_adv.X located in "<<Harmony Content Path>\wireless_apps_pic32cxbz2_wbz45\apps\ble\building_blocks\peripheral\ext_adv\firmware" using MPLAB X IDE

For more details on finding the Harmony content path, refer to Installing the MCC Plugin

Demo Description

This application example enables users to do scanning of extended advertisements (ADV_EXT_IND, ADV_AUX_IND PDU's). Scanning of CODED PHY (125 kbps) is enabled by default in the application. After programming the application example, on Reset "ExtAdv Scan Enable Success" will be printed in the terminal window and if there is a broadcaster sending extended advertisements the Green LED will toggle. If this broadcaster is another WBZ451 module programmed with “ext_adv.X” example it will print the application data sent in auxiliary packet - ADV_AUX_IND on TeraTerm. Toggling of Green LED denotes the reception of extended advertisements.

Testing

Users must use another WBZ451 Curiosity board configured as BLE Ext Adv

This section assumes that a user has already programmed the ext_adv and scan_ext_adv application on two WBZ451 Curiosity boards.

Data from advertiser is sent every 20 secs, Green LED is toggled when the observer device receives these extended advertisements.

Developing the Application from Scratch using MCC

This section explains the steps required by a user to develop this application example from scratch using MCC

1. Create a new MCC Harmony Project. For more details, refer to Creating a New MCC Harmony Project section.
2. Import component configuration – This step helps users setup the basic components and configuration required to develop this application. The imported file is of format .mc3 and is located in the path "<Harmony Content Path>\wireless_apps_pic32cxbz2_wbz45\apps\ble\building_blocks\central\scan_ext_adv\firmware\scan_ext_adv.X\" For more details on importing the component configuration, refer to Importing Existing App Example Configuration
   Note: Import and export functionality of component configuration will help users to start from a known working setup of configuration.

3. Accept dependencies or satisfiers, select Yes

4. Verify if the project graph window has all the expected configuration, as illustrated in the following figure.

   

Verifying Scan Configuration

1. Click on the BLE_Stack component in project graph, to open component configuration and configure as illustrated in the following figure.

   

Generating a Code

For more details on code generation, refer to MPLAB Code Configurator(MCC) Code Generation.

Files and Routines Automatically Generated by the MCC

After generating the program source from MCC interface by clicking Generate Code, the BLE configuration can be found in the following project directories

The OSAL , RF System, BLE System initialization routine executed during program initialization can be found in the project files. This initialization routine is automatically generated by the MCC

The BLE stack initialization routine excuted during application initialization can be found in project files. This initialization routine is automatically generated by the MCC. This call initializes and configures the GAP, GATT, SMP, L2CAP and BLE middleware layers.

Configuration for scanning extended advertisements is autogenerated

Note: app.c is auto generated and has a state machine based application code sample. Users can use this template to develop their application.

Header Files

• ble_gap.h(Header Files\config\default\ble\lib\include\) - This header file contains BLE GAP functions and is automatically included in the app.c file

Function Calls

MCC generates and adds the code to initialize the BLE Stack GAP, GATT, L2CAP and SMP in APP_BleStackInit() function

• APP_BleStackInit() is the API that will be called inside the applications initial state APP_STATE_INIT in app.c

User Application Development

Include

• definitions.h in all the files where UART will be used to print debug information

Note: definitions.h is not specific to just UART peripheral, instead it must be included in all application source files where peripheral functionality will be exercised

• User action is required as mentioned User Action

Enabling Scanning of Extended Advertisement

• BLE_GAP_SetExtScanningEnable (BLE_GAP_SCAN_MODE_OBSERVER, &extScan);

API's mentioned in this section are called in the Applications initial state - APP_STATE_INIT in app.c

// Enable Scanning the Ext Adv
uint16_t ret;
BLE_GAP_ExtScanningEnable_T extScan;
extScan.duration = 0x0;
extScan.enable = true;
extScan.filterDuplicates = BLE_GAP_SCAN_FD_DISABLE;
extScan.period = 0x0000;
ret = BLE_GAP_SetExtScanningEnable(BLE_GAP_SCAN_MODE_OBSERVER, &extScan );
if (ret == MBA_RES_SUCCESS)
       SERCOM0_USART_Write((uint8_t *)"ExtAdv Scan Enable Success\r\n", 28);

Configuring LED

1. Click on the System component in project graph, open Configuration Options and enable the following configurations.
2. Code will be added to GPIO_Initialize() available in Source Files\config\default\peripheral\gpio\plib_gpio.c.

Scanning Results

• BLE_GAP_EVT_EXT_ADV_REPORT event is generated upon finding advertisements on legacy channels

// code snippet to print ext adv data
    // GPIO will toggle if it can scan any EXT ADV PDU near based on BLE_GAP_SCAN_PHY chosen
    GPIOB_REGS->GPIO_PORTINV = 0x08;
    // length value of 19 is chosen as a filter as ext_adv example sends 19 bytes of data
    // user can modify filter mechanism based on their requirements
    if (p_event->eventField.evtExtAdvReport.length == 19)
    {
        SERCOM0_USART_Write((uint8_t *)"\r\n", 2);
        SERCOM0_USART_Write(&p_event->eventField.evtExtAdvReport.advData[5], 9);
    }

Users can exercise various other BLE Scanning functionalities by using BLE Stack API.

For more details, refer to Getting Started with Central Building Blocks section.