5.1.1.7 BLE Transparent UART Central with LE Coded Phy

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. See BLE Connection from Related Links.
4. See BLE Transparent UART from Related Links.
5. See BLE Multilink Transparent UART from Related Links.

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

Hardware Requirement

SDK Setup

Refer to Getting Started with Software Development from Related Links.

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\profiles_services\central_trp_uart_codedPhy\precompiled_hex.

2. Peripheral Device – Import and program the precompiled hex file: <Harmony Content Path>\wireless_apps_pic32_bz6\apps\ble\building_blocks\peripheral\profiles_services\peripheral_trp_uart_codedPhy\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_trp_uart.X located in <Harmony Content Path>\wireless_apps_pic32_bz6\apps\ble\building_blocks\central\profiles_services\central_trp_uart_codedPhy\firmware

3. Peripheral Device – Open and program the application peripheral_trp_uart.X" located in "<Harmony Content Path>\wireless_apps_pic32_bz6\apps\ble\building_blocks\peripheral\profiles_services\peripheral_trp_uart_codedPhy\firmware
4. For more details on how to find the Harmony Content Path, refer to Installing the MCC Plugin from Related Links.

Demo Description

Upon programming the demo application, central device (PIC32-BZ6) will start scanning for near by peripheral devices to connect. After a connection has been made data can be sent back and forth over UART between the two devices that are connected.

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.

Application data to be sent to the connected peripheral device must be entered in the terminal emulator.

Testing

Users must use another PIC32-BZ6 Curiosity Board configured as BLE Transparent UART Peripheral with LE Coded Phy, see BLE Transparent UART Peripheral with LE Coded Phy from Related Links.

Experience the Demo using two PIC32-BZ6 Curiosity boards configured as Peripheral and Central device.

This section assumes that a user has already programmed the peripheral_trp_uart_codedPhy and central_trp_uart_codedPhy application on two PIC32-BZ6 Curiosity Boards.

1. Board 1 – PIC32-BZ6 Curiosity Board Programmed with “peripheral_trp_uart_codedPhy” application.
   1. Open TeraTerm and configure as mentioned below:
      Terminal Settings:

      • Baud Rate/Speed – 115200
      • Parity – None
      • Data Bits – 8
      • Stop Bits – 1
      • Flow Control – None
      
   2. Reset the board, Upon reset, “Advertising” message is displayed on the Tera Term.
2. Board 2 – PIC32-BZ6 Curiosity Board Programmed with “central_trp_uart_codedPhy” applicaton.
   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, “Scanning” message is displayed on the TeraTerm.
   3. 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 (Board 1) and central device (Board 2) displays “Connected!” message on respective terminal windows.

Users can now start sending data back and forth between the central and peripheral device using the terminal emulator. Characters entered on either terminals will immediately be sent to the peer devices

Developing the Application from scratch using MPLAB Code Configurator

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\profiles_services\central_trp_uart_codedPhy\firmware\central_trp_uart.X

Verifying Scanning ,Connection and Transparent Profile Configuration

1. Select BLE_Stack component in project graph.

   
2. Select Transparent Profile component in project graph.

   

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.

Header Files

• ble_gap.h : This header file contains BLE GAP functions and is automatically included in the app.c file.

• ble_trspc.h:This header file associated with API’s and structures related to BLE Transparent Client functions for application user.

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.

• ble_trspc.h in app.c, BLE Transparent UART Server related API's are available here.

• osal/osal_freertos_extend.h in app_trsps_handler.c, OSAL related API's are available here.

• 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

BLE_GAP_SetExtScanningEnable(BLE_GAP_SCAN_MODE_OBSERVER, &extScan );

This API is called in the Applications initialstate - APP_STATE_INIT in app.c. Scan duration is 100 seconds. The 100 seconds scanning time will restart after a connection.

Scan Results and initiating a BLE connection

• BLE_GAP_EVT_EXT_ADV_REPORT event is generated upon finding Advertisements on legacy channels.

• BLE connection can be initiated by using the BLE_GAP_ExtCreateConnection.

Connected and Disconnected Events

• In app_ble_handler.c “BLE_GAP_EVT_CONNECTED” event will be generated when a BLE connection is completed.

Connection Handler

• Connection handle associated with the peer peripheral device needs to be saved for data exchange after a BLE connection.

• p_event->eventField.evtConnect.connHandle has this information.

  
  

Transmit Data

• Add APP_MSG_UART_CB to the generated APP_MsgId_T.

  

• BLE_TRSPC_SendData(conn_hdl , 1, &data); is the API to be used for sending data towards the central device.
  Note: The precompiled application example uses a UART callback to initiate the data transmission upon receiving a character on UART.

Example Implementation for Transmitting the received data over UART using the BLE_TRSPC_SendData API.

Receive Data

• BLE_TRSPC_EVT_RECEIVE_DATA is the event generated when data is sent from central device

• Users need to use the BLE_TRSPC_GetDataLength(&data_len) API to extract the length of application data received

• BLE_TRSPC_GetData(&conn_hdl, data); API is used to retrieve the data, conn_hdl is the value obtained from Connection Handler section

Example Implementation for printing the received data from peripheral device over UART

  /* TODO: implement your application code.*/
            uint16_t data_len;
            uint8_t *data;
            // Retrieve received data length
            BLE_TRSPC_GetDataLength(p_event->eventField.onReceiveData.connHandle, &data_len);
            while (data_len) {
                // Allocate memory according to data length
                data = OSAL_Malloc(data_len);
                if (data == NULL)
                    break;
                // Retrieve received data
                BLE_TRSPC_GetData(p_event->eventField.onReceiveData.connHandle, data);
                // Output received data to UART
                SERCOM0_USART_Write(data, data_len);
                // Free memory
                OSAL_Free(data);

                //check again
                data_len = 0;
                BLE_TRSPC_GetDataLength(p_event->eventField.onReceiveData.connHandle, &data_len);
            }

Where to go from Here

• See BLE Transparent UART Peripheral with LE Coded Phy from Related Links.