nRF21540 DK virtual COM port

The onboard interface MCU features a Universal Asynchronous Receiver/Transmitter (UART) interface through a virtual COM port.

The virtual COM port has the following features:

Flexible baud rate setting up to 1 Mbps
Note: Baud rate 921 600 is not supported through the virtual COM port.
Dynamic Hardware Flow Control (HWFC) handling
Tri-stated UART lines when no terminal is connected

The following table shows an overview of the UART connections on nRF52840 and the interface MCU.

Table 1. Relationship of UART connections on nRF52840 and interface MCU
GPIO nRF52840	nRF52840 UART
P0.05	RTS
P0.06	TXD
P0.07	CTS
P0.08	RXD

The UART signals are routed directly to the interface MCU. The UART pins connected to the interface MCU are tri-stated when no terminal is connected to the virtual COM port on the computer.

Note: The terminal software used must send a Data Terminal Ready (DTR) signal to configure the UART interface MCU pins.

The P0.05 (Request to Send (RTS)) and P0.07 (Clear to Send (CTS)) can be used freely when HWFC is disabled on the SoC.

Virtual COM port