5.1.1.4 BLE Connection

Recommended Readings

1. Getting Started with Application Building Blocks – See Building Block Examples from Related Links.

2. Getting Started with Peripheral Building Blocks – See Central Devices from Related Links.

3. FreeRTOS and BLE Stack Setup – See Central - FreeRTOS BLE Stack and App Initialize from Related Links.

4. See BLE Legacy Scan from Related Links.
5. See BLE Connection from Related Links.
6. See BLE Transparent UART from Related Links.

7. BLE Software Specification – See MPLAB® Harmony Wireless BLE in Reference Documentation from Related Links.

Hardware Requirement

SDK Setup

Software Requirement

Smartphone App

None

Programming the Precompiled Hex File or Application Example

Using MPLAB® X IPE:

1. Central Device – Import and program the precompiled hex file: <Harmony Content Path>\wireless_apps_pic32_bz6\apps\ble\building_blocks\central\central_conn\precompiled_hex
2. Peripheral Device – Import and program the precompiled hex file: <Harmony Content Path>\wireless_apps_pic32_bz6\apps\ble\building_blocks\Peripheral\Peripheral_conn\precompiled_hex
3. 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:

1. Perform the following the steps mentioned in Running a Precompiled Example. For more information, refer to Running a Precompiled Application Example from Related Links.
2. Central Device – Open and program the application central_conn.X located in <Harmony Content Path>\wireless_apps_pic32_bz6\apps\ble\building_blocks\central\central_conn\firmware.
3. Peripheral Device – Open and program the application peripheral_conn.X located in <Harmony Content Path>\wireless_apps_pic32_bz6\apps\ble\building_blocks\peripheral\peripheral_conn\firmware.

4. For more details on how to find the Harmony Content Path, refer to Installing the MCC Plugin from Related Links.

Demo Description

To experience this demo, users are required to use “central_connection” and “peripheral_connection” application examples. The two application example mentioned above will demonstrate a BLE Connection Establishment process. An Advertiser (Peripheral) will start connectable, scannable, undirected BLE advertisement and the scanner (Central) will receive the advertisements and initiate a BLE connection. enables users to transmit Connectable and Scannable Undirected BLE Advertisements. Demo application prints the status messages “Scanning” at the initiation of the scan process, “Connected!” upon successful connection, and “Disconnected” when the connection is lost, within a terminal emulator interface.

Testing

Users must use another PIC32-BZ6 Curiosity Board configured as peripheral connection, see BLE Connection from Related Links.

This section assumes that a user has already programmed the peripheral_conn and central_conn application on two PIC32-BZ6 Curiosity boards.

1. Board 1 – PIC32-BZ6 Curiosity Board Programmed with “peripheral_conn”
   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, “Advertising” message is displayed on the TeraTerm.
2. Board 2 – PIC32-BZ6 Curiosity Board Programmed with central_conn.
   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
   1. Reset the board. Upon reset, “Scanning” message is displayed on the TeraTerm.
   2. Upon finding peripheral device with public address {0xA1, 0xA2, 0xA3, 0xA4, 0xA5, 0xA6} message “Found Peer Node” will be displayed and a connection request will be initiated “Initiating connection”.

After connection establishment, both the peripheral device (Board1) and central device (Board2) will display “Connected!” message on respective terminal windows

Developing the Application from Scratch using MCC

1. Create a new harmony project. For more details, see Creating a New MCC Harmony Project from Related Links.
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_pic32_bz6\apps\ble\building_blocks\central\central_conn\firmware\central_conn.X.
   Note: Import and export functionality of Harmony component configuration will help users to start from a known working setup of MCC configuration
3. Accept dependencies or satisfiers when prompted.
4. Verify if the project graph window has all the expected configuration.

   

Verifying Scan and Connection Configuration

1. Select 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 from Related Links.

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

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. Initialization routine executed during program initialization can be found in the project files.

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

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

Header Files

• ble_gap.h: 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

• 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

Start Scanning

// Scanning Enabled
BLE_GAP_SetScanningEnable(true, BLE_GAP_SCAN_FD_ENABLE, BLE_GAP_SCAN_MODE_OBSERVER, 1000);
// Output the state string to UART
SERCOM0_USART_Write((uint8_t *)"Scanning \r\n", 11);

Scan Results and initiating a BLE connection

• BLE_GAP_EVT_ADV_REPORT event in app_ble_handler.c is generated upon finding advertisements on legacy channels

• BLE connection can be initiated by using the API BLE_GAP_CreateConnection(&createConnParam_t);

  // code snippet to filter scan results and initiate connection
  if ((p_event->eventField.evtAdvReport.addr.addr[0] == 0xA1 && p_event->eventField.evtAdvReport.addr.addr[1] == 0xA2) ||
    (p_event->eventField.evtAdvReport.addr.addr[0] == 0xB1 && p_event->eventField.evtAdvReport.addr.addr[1] == 0xB2) ||
    (p_event->eventField.evtAdvReport.addr.addr[0] == 0xC1 && p_event->eventField.evtAdvReport.addr.addr[1] == 0xC2))
{
    SERCOM0_USART_Write((uint8_t *)"Found Peer Node\r\n", 17);
    BLE_GAP_CreateConnParams_T createConnParam_t;
    createConnParam_t.scanInterval = 0x3C; // 37.5 ms 
    createConnParam_t.scanWindow = 0x1E; // 18.75 ms
    createConnParam_t.filterPolicy = BLE_GAP_SCAN_FP_ACCEPT_ALL;
    createConnParam_t.peerAddr.addrType = p_event->eventField.evtAdvReport.addr.addrType;
    memcpy(createConnParam_t.peerAddr.addr, p_event->eventField.evtAdvReport.addr.addr, GAP_MAX_BD_ADDRESS_LEN);
    createConnParam_t.connParams.intervalMin = 0x10; // 20ms
    createConnParam_t.connParams.intervalMax = 0x10; // 20ms
    createConnParam_t.connParams.latency = 0;
    createConnParam_t.connParams.supervisionTimeout = 0x48; // 720ms
    SERCOM0_USART_Write((uint8_t *)"Initiating Connection\r\n", 23);
    BLE_GAP_CreateConnection(&createConnParam_t);
}

Connected and Disconnected Events

• All the possible GAP, GATT, SMP and L2CAP Event handlers are available in file app_ble_handler.c, users can implement application code to denote connection state here. BLE_GAP_EVT_CONNECTED event is generated after a successful BLE connection with peripheral device

  // Connected EVT
  SERCOM0_USART_Write((uint8_t *)"Connected\r\n", 11);
  //Disconnected EVT
  SERCOM0_USART_Write((uint8_t *)"Disconnected\r\n", 15);
  

  

Scan Timeout Event

• In app_ble_handler.c BLE_GAP_EVT_SCAN_TIMEOUT event is generated when BLE Scan duration expires.

  SERCOM0_USART_Write((uint8_t *)"Scan Completed\r\n", 17);

  

Where to go from Here

See BLE Transparent UART from Related Links.