The radio_test application doesn't receive input on nrf52840 chip, while the echo_bot example does.

[xiongwei.wang]

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?

[xiongwei.wang]

I find the true problem, the following function execution failes. 

```c

err = sys_notify_fetch_result(&clk_cli.notify, &res);

```

I printed the err value and compare it with the offciail board's output. The err should be zero but on my custom board is -11.
And I examined the function:
```c

static inline int sys_notify_fetch_result(const struct sys_notify *notify,
int *result)
{
       __ASSERT_NO_MSG(notify != NULL);
       __ASSERT_NO_MSG(result != NULL);
      int rv = -EAGAIN;

      if (sys_notify_get_method(notify) == SYS_NOTIFY_METHOD_COMPLETED) {
           rv = 0;
          *result = notify->result;
     }

     return rv;
}

```
I found the `-EAGAIN` is `-11`, which means the condition `sys_notify_get_method(notify) == SYS_NOTIFY_METHOD_COMPLETED` is

never satisfied.

[xiongwei.wang]

But I haven't yet solved this problem. I lost track of this thread. Does anybody know the reason?