How can i change RX TX pin of UART?

Question

Hello,
because of my mistake, rx tx pin was not cross connected. 
 So i want to swap rx tx pin on nrf51822. 
 In the example ble_app_uart_s130_pca10028, i change the code in main.c 
 const app_uart_comm_params_t comm_params =
{
RX_PIN_NUMBER, //RX_PIN_NUMBER=11
TX_PIN_NUMBER, //TX_PIN_NUMBER=9;
RTS_PIN_NUMBER,
CTS_PIN_NUMBER,
APP_UART_FLOW_CONTROL_ENABLED,
false,
UART_BAUDRATE_BAUDRATE_Baud38400
}; 
 to 
 const app_uart_comm_params_t comm_params =
{
9,
11,
RTS_PIN_NUMBER,
CTS_PIN_NUMBER,
APP_UART_FLOW_CONTROL_ENABLED,
false,
UART_BAUDRATE_BAUDRATE_Baud38400
}; 
 After upload the firmware, i test uart using nRF Toolbox app. 
 
 disconnect rx tx pin physically, pairing BLE -> well paired. 
 connect rx tx pin physically -> Error 6:The connection has timed out unexpectedly occur and break the pairing. 
 
 Why this error is occur? 
 When i try not swapped code(origin example) crossing rx tx pin on MCU, 
 this error is not occurred.

psharma · Accepted Answer

Is this on the PCA10028 board, or a custom board?
On PCA10028, nRF51 pin 11 (RX) is connected to TX of J-Link virtual serial port, and pin 9 (TX) is connected to RX of J-Link virtual serial port. 
 When you are swapping these two in your main.c, it will mostly likely cause an error as the pins are hard-wired, and the J-link is pulling up one of these pins (speculating) .
If you need to do a loop-back test, you can use any other freely available pins that are not hardwired, short them, and disable flow control. 
 In case you are using a custom board and swapping these pins, then make sure you have the BOARD_CUSTOM flag set in the compiler. Also you have flow control enabled, so take care of that as well (on custom board).

How can i change RX TX pin of UART?

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