SLAU678C March 2016 – November 2022
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 PC host side. This can be used to create graphical user interfaces (GUIs) and other programs on the PC that communicate with the LaunchPad development kit.
Figure 2-5 shows the pathway of the backchannel UART. The backchannel UART is the UART on eUSCI_A0. This UART channel is separate from the UART on the 40-pin BoosterPack plug-in module connector (eUSCI_A3).
On the host side, a virtual COM port for the application backchannel UART is generated 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 (see Figure 2-6).
The backchannel UART is the MSP Application UART1 (COM13) port. In this case, Figure 2-6 shows COM13, but this port can vary from one host PC to the next. Identify the correct COM port and configure it in the host application according to its documentation. Then open the port and begin communication to it from the host.
On the target MSP430FR5994 side, the backchannel is connected to the eUSCI_A0 module. The eZ-FET has a configurable baud rate; therefore, it is important that the PC application configures the baud rate to be the same as what is configured on the eUSCI_A0.