nRF52 DK v1.1.x

Dynamic Hardware Flow Control (HWFC) handling

When the interface MCU receives a DTR signal from a terminal, it performs automatic HWFC detection.

Automatic HWFC detection is done by driving P0.07 (CTS) from the interface MCU and evaluating the state of P0.05 (RTS) when the first data is sent or received. If the state of P0.05 (RTS) is high, HWFC is assumed not to be used. If HWFC is not detected, both CTS and RTS can be used freely by the nRF application.

After a power-on reset of the interface MCU, all UART lines are tri-stated when no terminal is connected to the virtual COM port. Due to the dynamic HWFC handling, if HWFC has been used and detected, P0.07 (CTS) will be driven by the interface MCU until a power-on reset has been performed or until a new DTR signal is received and the detection is redone. To ensure that the UART lines are not affected by the interface MCU, the solder bridges for these signals can be cut and later resoldered if needed. This might be necessary if UART without HWFC is needed while P0.05 (RTS) and P0.07 (CTS) are used for other purposes.