I encounter this problem:
The radio_test application works correctly on the official nrf52840dk board, but cannot receive input commands on my custom product board.
However, the echo_bot example works fine on the same custom board.
I tried adding the following configuration:
```conf
CONFIG_CONSOLE=y
CONFIG_SERIAL=y
CONFIG_UART_CONSOLE=y
CONFIG_SHELL_BACKEND_SERIAL=y
```
I also tried to disable hardware flow control in code:
```c
nrf_uarte_hwfc_pins_disconnect(NRF_UART0);
```
I noticed that echo_bot doesn't disable hardware flow control but still works properly.
My product uses the nRF52840 chip connected through an external J-Link, and I'm using NCS v2.9.0.
Questions: What should I do? What configuration or code do I need to add to solve this problem?