2.2.4 Application (or Backchannel) UART

The backchannel UART allows communication with the USB host that is not part of the target application’s main functionality. This is very useful during development and also provides a communication channel to the host PC. Data from this communication channel can be used to create a graphical user interface (GUI) or other programs on the PC that communicate with the LaunchPad development kit.

Figure 6 shows the pathway of the backchannel UART. The backchannel UART is the UART on eUSCI_A0.

A virtual COM port for the application backchannel UART is generated on the host when the LaunchPad development kit enumerates on the host. You can use any PC application that interfaces with COM ports, including terminal applications like Hyperterminal or Docklight, to open this port and communicate with the target application. You need to identify the COM port for the backchannel. On Windows PCs, Device Manager can assist.

The backchannel UART is the "MSP Application UART1" port. In this case, Figure 7 shows COM13, but this port can vary from one host PC to the next. After you identify the correct COM port, configure it in your host application according to its documentation. You can then open the port and begin communication to it from the host.

On the target MSP430FR2476 MCU, the backchannel is connected to the eUSCI_A0 module. The eZ-FET has a configurable baud rate, and it is important to configure the PC application with the same baud rate as the eUSCI_A0.