3.1.2.8 BLE Transparent UART Peripheral with LE Coded Phy

Introduction

This document will help users create a peripheral device and send/receive characters between two connected BLE devices over the Microchip proprietary Transparent UART Profile with LE Coded PHY. The peripheral device will be a WBZ451 Curiosity board and the central device another WBZ451 board.

Users of this document can choose to just run the precompiled Application Example hex files on the WBZ451 Curiosity boards and experience the demo or can go through the steps involved in developing this application from scratch.

These examples each build on top of one another. We strongly recommend that you follow the examples in order, by learning the basic concepts first before progressing to the more advanced topics.

Hardware Requirement


Tool	Quantity
WBZ451 Curiosity Board	2
Micro USB cable	2

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 MPLABX IPE

Import and program the Precompiled Hex file: <Harmony Content Path>\wireless_apps_pic32cxbz2_wbz45\apps\ble\building_blocks\peripheral\profiles_services\peripheral_trp_uart_codedPhy\hex\peripheral_trp_uart_codedPhy.X.production.signed.hex
Import and program the Precompiled Hex file: <Harmony Content Path>\wireless_apps_pic32cxbz2_wbz45\apps\ble\building_blocks\central\profiles_services\central_trp_uart_codedPhy\hex\central_trp_uart_codedPhy.X.production.signed.hex
For more details on the steps, go to Programming A Device.

Note: Ensure to choose the correct Device and Tool information

Programming the Application using MPLABX IDE

Follow the steps mentioned in of Running a Precompiled Example.
Open and program the Application: <Harmony Content Path>\wireless_apps_pic32cxbz2_wbz45\apps\ble\building_blocks\peripheral\profiles_services\peripheral_trp_uart_codedPhy\firmware\peripheral_trp_uart_codedPhy.X
3. Open and program the Application: <Harmony Content Path>\wireless_apps_pic32cxbz2_wbz45\apps\ble\building_blocks\central\profiles_services\central_trp_uart_codedPhy\firmware\central_trp_uart_codedPhy.X

For more details on how to find the Harmony Content Path, refer to Installing the MCC Pluggin.

Demo Description

Upon programming the application, the WBZ451 Curiosity board will start Connectable Extended Advertisements with LE Coded PHY. Another WBZ451 board as a central device scanning for these advertisements will connect to the device. After a connection has been established, data can be sent back and forth over UART between the two devices. Demo will print “Ext Advertising…” indicating the start of advertisements on a terminal emulator like Tera Term. Application data to be sent to the connected central device should also be entered in the terminal emulator.

Testing

Using micro USB cables, connect the Debug USB on the Curiosity boards to a PC
Program the precompiled hex files or application examples as mentioned.

Note: One WBZ451 board should be programmed as a peripheral UART Coded PHY and the other board as a central UART Coded PHY.
Open the Tera Term of the board programmed as peripheral_trp_uart_codedPhy and set the “Serial Port” to USB Serial Device and “Speed” to 115200. Press SW1 to reset the board. Tera Term should display the following message.
For more details on how to set the “Serial Port” and “Speed”, refer to COM Port Setup
Open the Tera Term of the board programmed as central_trp_uart_codedPhy and set the “Serial Port” to USB Serial Device and “Speed” to 115200. Press SW1 to reset the board. Tera Term should display the following message.
Exchange data between the peripheral and central devices by typing on one terminal and seeing it on the other and vice versa.

Developing the Application from Scratch using MPLAB Code Configurator

This section explains the steps required by a user to develop this application example from scratch using the MPLAB Code Configurator.

Note: It is recommended that new users of the MPLAB Code Configurator to go through this overview

Create a new MCC Harmony Project
2. To setup the basic components and configuration required to develop this application, import component configuration: <Harmony Content Path>\wireless_apps_pic32cxbz2_wbz45\apps\ble\building_blocks\peripheral\profiles_services\peripheral_trp_uart_codedPhy\firmware\peripheral_trp_uart_codedPhy.X\peripheral_trp_uart_codedPhy.mc3 For more details, refer to Import existing App Example Configuration

Note: Import and Export functionality of the Harmony component configuration will help users to start from a known working setup of the MCC configuration.
To accept dependencies or satisfiers, select "Yes"
Verify if the Project Graph window has all the expected configuration

Verify Advertisement,Connection and Transparent UART Profile Configuration

Select the BLE Stack component in the Project Graph and configure the following in the Configuration Options panel graph
Select the Transparent Profile component in the project graph and configure the following

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 the MCC interface by clicking Generate Code, the BLE configuration source and header files can then 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 executed 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.

Figure 3-169. .

Autogenerated, advertisement data format


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_ble\app_trsps_handler.c	All Transparent UART Server related Event handlers
ble_trsps.c	All Transparent Server Functions for user application

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

Header Files

ble_gap.h contains BLE GAP functions and is automatically included in app.c
ble_trsps.h is associated with APIs and structures related to the BLE Transparent Client functions for the application user

Function Calls

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

APP_BleStackInit() is the API that will be called inside the Applications Initial State APP_STATE_INIT in app.c

User Application Development

Include

User Action is required
ble_trsps.h in app.c contains BLE Transparent UART Server related APIs
osal/osal_freertos_extend.h in app_trsps_handler.c contain OSAL related APIs
definitions.h must be included in all the files where UART will be used to print debug information

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

Set PUBLIC Device Address in app_ble.c

BLE_GAP_SetDeviceAddr(&devAddr);

    BLE_GAP_Addr_T devAddr;
    devAddr.addrType = BLE_GAP_ADDR_TYPE_PUBLIC;
    devAddr.addr[0] = 0xA1;
    devAddr.addr[1] = 0xA2;
    devAddr.addr[2] = 0xA3;
    devAddr.addr[3] = 0xA4;
    devAddr.addr[4] = 0xA5;
    devAddr.addr[5] = 0xA6;

    // Configure device address
    BLE_GAP_SetDeviceAddr(&devAddr);

Start Advertisement in app.c

- BLE_GAP_SetExtAdvEnable(true, 0x01, &extAdvEnableParam);

Connected & 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_C to the generated APP_MsgId_T
Figure 3-170. .
BLE_TRSPS_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 for transmitting over UART using the BLE_TRSPS_SendData() API

uint16_t conn_hdl;// connection handle info captured @BLE_GAP_EVT_CONNECTED event
uint16_t ret;
uint8_t uart_data;
void uart_cb(SERCOM_USART_EVENT event, uintptr_t context)
{
  APP_Msg_T   appMsg;  
  // If RX data from UART reached threshold (previously set to 1)
  if( event == SERCOM_USART_EVENT_READ_THRESHOLD_REACHED )
  {
    // Read 1 byte data from UART
    SERCOM0_USART_Read(&uart_data, 1);
    appMsg.msgId = APP_MSG_UART_CB;
    OSAL_QUEUE_Send(&appData.appQueue, &appMsg, 0);     
  }
}

void APP_UartCBHandler()
{
    // Send the data from UART to connected device through Transparent service
    BLE_TRSPS_SendData(conn_hdl, 1, &uart_data);      
}
  // Register call back when data is available on UART for Peripheral Device to send
// Enable UART Read
SERCOM0_USART_ReadNotificationEnable(true, true);
// Set UART RX notification threshold to be 1
SERCOM0_USART_ReadThresholdSet(1);
// Register the UART RX callback function
SERCOM0_USART_ReadCallbackRegister(uart_cb, (uintptr_t)NULL);

Figure 3-172. .

else if(p_appMsg->msgId==APP_MSG_BLE_STACK_LOG)
{
   // Pass BLE LOG Event Message to User Application for handling
   APP_BleStackLogHandler((BT_SYS_LogEvent_T *)p_appMsg->msgData);
}
else if(p_appMsg->msgId==APP_MSG_UART_CB)
{
   // Pass BLE UART Data transmission target BLE UART Device handling
   APP_UartCBHandler();
}

Receive Data

BLE_TRSPS_EVT_RECEIVE_DATA is the event generated when data is sent from the central device
Use the BLE_TRSPS_GetDataLength(p_event->eventField.onReceiveData.connHandle, &data_len); API to extract the length of the application data received
BLE_TRSPS_GetData(p_event->eventField.onReceiveData.connHandle, data); API is used to retrieve the data
Note: BLE_TRSPS_Event_T p_event structure stores the information about the BLE transparent UART callback functions
Example for printing the received data from the central device over UART

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