5.1.1.3 BLE Scanning Extended Advertisements

This section describes in detail the scanning of Extended Advertisements (ADV_EXT_IND, ADV_AUX_IND) on the WBZ351 Curiosity board. For a successful scan of Extended Advertisement user needs to have a broadcaster transmitting these Advertisements. In Bluetooth Low Energy, a central or observer always starts with scanning.

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

Users can choose to either run the precompiled Application Example hex file provided on the WBZ351 Curiosity Board or follow the steps to develop the application from scratch.

It is recommended to follow the examples in sequence to understand the basic concepts before progressing to the advanced topics.

Hardware Requirement

Table 5-3. Hardware Prerequisites
S. No.	Tool	Quantity
1	WBZ351 Curiosity Board	2
2	Micro USB cable	2

SDK Setup

Refer to Getting Started with Software Development from Related Links.

Software Requirement

To install Tera Term tool, refer to the Tera Term web page in Reference Documentation from Related Links.

Smartphone Application

None

Programming the Precompiled Hex File or Application Example

Using MPLAB® X IPE:

Central Device – Import and program the precompiled hex file: <Discover Path>\wireless_apps_pic32cxbz3_wbz35\apps\ble\building_blocks\central\scan_ext_adv\hex.
Peripheral Device – Import and program the precompiled hex file: <Discover Path>\wireless_apps_pic32cxbz3_wbz35\apps\ble\building_blocks\peripheral\ext_adv\hex.
For detailed steps, refer to Programming a Device in MPLAB® IPE in Reference Documentation from Related Links.

Note: Ensure to choose the correct Device and Tool information.

Using MPLAB® X IDE:

Perform the following the steps mentioned in Running a Precompiled Example. For more information, refer to Running a Precompiled Application Example from Related Links.
Central Device – Open and program the application scan_ext_adv.X located in <Discover Path>\wireless_apps_pic32cxbz3_wbz35\apps\ble\building_blocks\central\scan_ext_adv\firmware.
Peripheral Device – Open and program the application ext_adv.X located in <Discover Path>\wireless_apps_pic32cxbz3_wbz35\apps\ble\building_blocks\peripheral\ext_adv\firmware.
For more details on how to find the Discover path, refer to Download Application Example from Discover in Running a Precompiled Application Example from Related Links.

Demo Description

This application example enables users to scan for extended advertisements (ADV_EXT_IND, ADV_AUX_IND PDUs). Scanning of the CODED PHY (125 kbps) is enabled by default in the application. After programming the application example, upon Reset, “ExtAdv Scan Enable Success” will be printed in the terminal window and if there is a broadcaster sending extended advertisements the Green LED toggles. If this broadcaster is another WBZ351 Module programmed with ext_adv.X example it prints the application data sent in auxiliary packet ADV_AUX_IND on Tera Term. Toggling of the green LED indicates the reception of extended advertisements.

Tera Term Configuration

Baud Rate/Speed – 115200 (as configured in SERCOM configuration)
Parity – None
Data Bits – 8
Stop Bits – 1
Flow Control – None

Testing

Users must use another WBZ351 Curiosity Board configured as BLE Extended Advertisements, see BLE Extended Advertisements from Related Links.

This section assumes that a user has already programmed the ext_adv and scan_ext_adv application on two WBZ351 Curiosity boards.

Board 1 – WBZ351 Curiosity board programmed with extended advertisements
1. Open Tera Term and configure as mentioned below:
  Terminal Settings
  - Baud Rate/Speed – 115200 (as configured in SERCOM configuration)
  - Parity – None
  - Data Bits – 8
  - Stop Bits – 1
  - Flow Control – None
2. Reset the board. Upon reset, the Ext Adv Enable message appears on the Tera Term.
Board 2 – WBZ351 Curiosity Board Programmed with extended advertisements scan
1. Open TeraTerm and configure as mentioned below:
  Terminal Settings
  - Baud Rate/Speed – 115200 (as configured in SERCOM configuration)
  - Parity – None
  - Data Bits – 8
  - Stop Bits – 1
  - Flow Control – None
2. Reset the board. Upon reset, the ExtAdv Scan Enable Success message appears on the Tera Term.
3. Microchip message will be displayed as soon the WBZ351 Module performs an extended advertisement scan.

Green LED is toggled when the observer device receives these extended advertisements. Sometimes, the PIC32CX-BZ3/PIC32CX-BZ36 device appears twice simultaneously on Tera Term. During this time, the green LED toggles rapidly, indicating no actual toggle occurred.

Developing the Application from Scratch using MCC

Follow the steps below to build the application manually:

Note: It is recommended for the new users of the MPLAB Code Configurator to refer MPLAB® Code Configurator (MCC) User’s Guide in Reference Documentation from Related Links.

Create a new harmony project. For more details, see Creating a New MCC Harmony Project from Related Links.
Import Component Configuration - This step helps users to setup the basic components and configuration required to develop this application. The imported file is of format .mc4 and is located in the path <Discover Path>\wireless_apps_pic32cxbz3_wbz35\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 from Related Links.
Note: Import and export functionality of component configuration will help users to start from a known working setup of configuration.
Accept Dependencies or Satisfiers.
1. If prompted to resolve dependencies or add required modules. Click Yes.
2. MPLAB® MCC automatically adds any required drivers or middleware.
Verify Project Graph.
In Project Graph window, confirm that all expected components are present. For more details, see the following figure.
Figure 5-22. Project Graph

Verifying Scan Configuration

Open the Project Graph
1. In MPLAB® X IDE, with MCC open, locate the Project Graph tab. In the Project Graph tab, the user can see all the components and their relationships to the project.
Select the BLE Stack Component
1. Click on the BLE Stack component in project graph. This opens the “BLE Stack” component Configuration Options tab.
2. In the “BLE Stack” Configuration Options tab, the user can set the parameters as per the requirement illustrated in the following figure.
  Figure 5-23. BLE Stack Configuration

Generating a Code

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

Files and Routines Automatically Generated by the MCC

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

Initialization routines for OSAL, RF System, and BLE System are auto-generated by the MCC. See OSAL Libraries Help in Reference Documentation from Related Links.

The project files contain the BLE stack initialization routine executed during application initialization. The MCC automatically generates this initialization routine. This call initializes and configures the GAP, GATT, SMP, L2CAP, and BLE middleware layers.

Configuration for scanning extended advertisements is auto-generated.

Table 5-4. Source Files
Source Files	Usage
`app.c`	Application State machine, includes calls for Initialization of all BLE stack (GAP,GATT, SMP, L2CAP) related component configurations
`app_ble\app_ble.c`	Source code for the BLE stack related component configurations, code related to function calls from `app.c`
`app_ble\app_ble_handler.c`	All GAP, GATT, SMP and L2CAP Event handlers
`app_user_edits.c`	User Code Change instruction
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 the APP_BleStackInit() function.
- APP_BleStackInit() is the API that will be called inside the application’s Initial state APP_STATE_INIT in app.c.

User Application Development

Include

Include the user action. For more information, refer to User Action from Related Links.
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.

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. This opens Configuration Options tab and enable the following configurations.
2. Code will be added to GPIO_Initialize() available in Source Files\config\default\peripheral\gpio\plib_gpio.c.
Figure 5-28. System Component Configuration

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);
    }

Note: Users can explore more BLE Advertisement functionalities using the BLE Stack APIs. For more information, refer to BLE Stack in Reference Documentation from Related Links.

Where to Go from Here

See Central Devices from Related Links.