THE PROBLEM OF UART

I download the SDK  at  https://www.nordicsemi.com/eng/nordic/Products/nRF5-SDK/nRF5-SDK-zip/59011 . When I used  "nRF5_SDK_15.0.0_a53641a\examples\ble_central\ble_app_uart_c " ,  it run ok.  But  when I  changed  the  define of RX_PIN_NUMBER  at  pca10040.h . The software doesn't run. The J-LINK shows  "  0> <error> app: Communication error occurred while handling UART. ".

And i found RX_PIN_NUMBER must be defined to 8.  if the RX_PIN_NUMBER be defined to any number, the software doesn't run.

WHY? please help me. thank you.  My board is uesd 52832.

  • Why do you change the RX pin? Do you connect it to something else? If you connect it to something else, do you also connect the other device to ground?

    If you just change the pin number, but don't connect anything to it, it will be left floating in the wind and will pick up noise. The UART will then believe that the noise is actual data, but not be able to make sense of it. Then it generates a Communication error.