3.12 Bluetooth® Low Energy Multilink Transparent UART

This section helps users to create a Multilink central device and sending/receiving characters between connected BLE devices over Microchip proprietary Transparent UART Profile. The Multilink central enables users to connect multiple peripheral devices to a central device. The central and peripheral devices in this tutorial are the Curiosity boards.

Users can either choose to run the precompiled application example .hex file on the Curiosity Board and experience the demo or can go through the steps involved in developing this application from scratch.

These examples are incrementally structured upon one another. Recommendation is to follow the examples in order, by learning the basic concepts first and then progressing to the more advanced topics.

Recommended Reading

  1. BLE Software Specification
  2. Getting Started with WME Bluetooth Low Energy Applications
Note: Refer to the Getting Started with WME Bluetooth Low Energy Applications from Related Links

Hardware Requirement

Table 3-23. Hardware Requirement
Tool Qty
Curiosity Board3 (min)
Micro USB cable3

Software

  • MPLAB X IPE: For programming the precompiled hex file.
  • MPLAB X IDE: For programming the application example.
  • Teraterm: Terminal Emulator for displaying UART output.

Programming the Precompiled Hex File or Application Example

Programming the .hex File using MPLAB X IPE

  1. Central Device : Precompiled .hex file is located in “<Harmony Content Path>\wireless_apps_ble\apps\multilink\hex” folder
  2. Peripheral Device: Precompiled .hex file is located in “<Harmony Content Path>\wireless_apps_ble\apps\peripheral_trp_uart\hex” folder
  3. For more information on the programming steps, refer to the Programming a Device in MPLAB IPE.
    Note: Users must choose the correct device and tool information.

Programming the Application using MPLAB X IDE

  1. Follow the steps mentioned in Running a Precompiled Example
  2. Central Device : Open and program the application example “multilink_xxxx.X” where xxxx refer to device (for example: WBZ451, project file: multilink_wbz451.X) located in “<Harmony Content Path>\wireless_apps_ble\apps\multilink\firmware” using MPLAB X IDE
  3. Peripheral Device : Open and program the application example “peripheral_trp_uart_xxxx.X” where xxxx refer to device (for example: WBZ451, project file: peripheral_trp_uart_wbz451.X) located in “<Harmony Content Path>\wireless_apps_ble<\apps\peripheral_trp_uart\firmware" using MPLAB X IDE

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

Demo Description

Developing the Application from Scratch using MCC

This section explains the steps required by a user to develop this application example from scratch using MCC
Note: It is recommended that new users of MCC to go through the MPLAB® Code Configurator (MCC) User's Guide.
  1. Create a new MCC Harmony Project by selecting the device. For more details, refer to Creating a New MCC Harmony Project.
  2. Launch the MCC from the toolbar as illustrated below. The project graph will open with the default components.
    Figure 3-132. MCC
  3. In the Device Resources window, expand Libraries > Harmony > Wireless > Application Services. Then, click the Plus Symbol to add the BLE Config App Service Component to the project
    Figure 3-133. BLE Config App Service
  4. All BLE Stack related components will be added into the project graph. Accept dependencies or satisfiers by selecting Yes.
  5. For configuring BLE Config App Service component based on the device refer to Adding BLE Config App Service Component to Project Graph and Selecting the Device in Getting Started with WME Bluetooth Low Energy Applications from Related Links. Additionally Change BLE Config App Service component configuration Number of links to “3” as illustrated in the following figure.
    Figure 3-134. BLE Config App Service
  6. Add and verify Transparent App Service Component setting as illustrated in the following figure
    Figure 3-135. Transparent App Service
  7. To enable digital and communication interfaces, refer to Enabling Digital Input/Output and Communication Interfaces Through System Hardware Definition (SHD) component in Getting Started with WME Bluetooth Low Energy Applications from Related Links.
  8. For FreeRTOS component settings refer to Configuring FreeRTOS in Getting Started with WME Bluetooth Low Energy Applications from Related Links.
  9. For WBZ451
    1. Verify if the project graph window has all the expected components, as illustrated in the following figure:
      Figure 3-136. Project Graph
    2. Verify FreeRTOS Component setting for Tick Mode and Include xTaskAbortDelay as illustrated in the following figure:
      Figure 3-137. FreeRTOS Configuration
      Figure 3-138. FreeRTOS Configuration
  10. For WBZ351
    1. Verify if the project graph window has all the expected components, as illustrated in the following figure:
      Figure 3-139. Project Graph
    2. Verify FreeRTOS Component setting for Tick Mode and modify as illustrated in the following figure.
      Figure 3-140. FreeRTOS Configuration
    3. Verify SERCOM Component setting for Enable Run in Standby and modify as illustrated in the following figure
      Figure 3-141. SERCOM Configuration
  11. Change BLE Stack Component configuration as illustrated in the following figure.
    Figure 3-142. BLE Stack Configuration

Generating a Code

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

Files Containing user Application Code

Source code for the application will be generated from the MCC interface by clicking on Generate Code. User can add or edit the code in the highlighted files as illustrated in the following figure.
Figure 3-143. Files
Details on files that user can modify
Table 3-24. Source Files
Source FilesUsage
app.cApplication State machine, includes calls for Initialization of all BLE stack (GAP,GATT, SMP, L2CAP) related component configurations
app_ble_callbacks.cAll the event functions related to GAP, GATT, SMP and L2CAP events that user can use or modify .
app_trspc_callbacks.cAll the event functions related to trspc event handles that user can use or modify.
app_utility.cContains generic utility functions that serve the purpose of providing reusable, common functionalities that can be applied across various parts of a program.
Note: app.c is auto generated and has a state machine based application code sample. Users can use this template to develop their application. Main application logic is implemented in void APP_Tasks() function.
Figure 3-144. app.c
.
Figure 3-145. app.c

References

  • Bluetooth Low Energy Multilink Transparent UART Application for: WBZ451
  • Bluetooth Low Energy Multilink Transparent UART Application for: WBZ351