4.1.1.4 Bluetooth®LE Connection

Hardware Requirement

Software Requirement

Programming the Precompiled Hex File or Application Example

Using MPLAB® X IPE:

1. Central Device – Precompiled .hex file is located in <Harmony Content Path>\wireless_apps_pic32_bw1\apps\ble\central\central_conn\hex folder.
2. Peripheral Device – Precompiled .hex file is located in <Harmony Content Path>\wireless_apps_pic32_bw1\apps\ble\peripheral\peripheral_Connect\hex folder.
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_bw1\apps\ble\central\central_conn\firmware.
3. Peripheral Device – Open and program the application BLE_Connect.X located in <Harmony Content Path>\wireless_apps_pic32_bw1\apps\ble\peripheral\peripheral_Connect.

4. For more details on finding the Harmony content path, refer to Installing the MCC Plugin from Related Links.

Testing

1. Users must use two PIC32WM-BW1 Curiosity Board configured as Peripheral and Central device, to experience this demo.
2. Board 1 – PIC32WM-BW1 Curiosity Board Programmed with “BLE_Connect” application. Open Tera Term and configure as mentioned below:

   Terminal Settings:

   • Baud Rate/Speed – 115200
   • Parity – None
   • Data Bits – 8
   • Stop Bits – 1
   • Flow Control – None
3. Reset the board, Upon reset, “BW1-Advertising” message is displayed on the TeraTerm. It will start connectable, scannable, undirected BLE advertisement.
4. Board 2 – PIC32WM-BW1 Curiosity Board Programmed with “central_conn” application. Open TeraTerm and configure as mentioned below:

   Terminal Settings:

   • Baud Rate/Speed – 115200
   • Parity – None
   • Data Bits – 8
   • Stop Bits – 1
   • Flow Control – None
5. Reset the board. Upon reset, “BW1-Scanning” message is displayed on the Tera Term.
6. Central device (Board 2) will start scanning for nearby peripheral devices to connect. 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”.
   Note: Scanner is configured to scan only for 100 seconds, user must ensure the peer device is advertising.
7. After connection establishment, both the peripheral device (Board1) and central device (Board2) will display “Connected!” message on respective terminal windows

Project Graph

Verifying Scan, Connection and Transparent Profile 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

The OSAL, RF System and BLE System initialization routine executed during program initialization can be found in the project file. 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 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

1. 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

2. Start Scanning

   // Scanning Enabled
   BLE_GAP_SetScanningEnable(true, BLE_GAP_SCAN_FD_ENABLE, BLE_GAP_SCAN_MODE_OBSERVER, 1000);
   
   // Output the status string to UART
   SERCOM0_USART_Write((uint8_t *)"BW1-Scanning \r\n", 14);

   This API is called in the application’s initial state – APP_STATE_INIT in app.c. Scan duration is 100 secs.

   

3. 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);

     // Filter Devices based of Address, for this example address checking only 2 bytes
   if (p_event->eventField.evtAdvReport.addr.addr[0] == 0xA1 && p_event->eventField.evtAdvReport.addr.addr[1] == 0xA2)
   {
   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);
   }

4. 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

     SERCOM0_USART_Write((uint8_t *)"Connected!\r\n", 12);
     SERCOM0_USART_Write((uint8_t *)"Disconnected\r\n", 15);

     

5. 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);