Direct test mode change pin assign

[kevin seo]

hello.
I'm testing direct test mode.(nRF52840-DK)

default pin is
#define RX_PIN_NUMBER 8
#define TX_PIN_NUMBER 6
#define CTS_PIN_NUMBER 7
#define RTS_PIN_NUMBER 5

I want change
#define RX_PIN_NUMBER 2
#define TX_PIN_NUMBER 29
#define CTS_PIN_NUMBER 7
#define RTS_PIN_NUMBER 5

But when I changed only the pin number,
NRF_DRV_UART_EVT_ERROR/APP_UART_COMMUNICATION_ERROR error occurred.
Why does this error occur when I only change the pin number to 2, 29?
And how can I solve this problem.

[haakonsh]

From Connector interface: 
P0.05, P0.06, P0.07, and P0.08 are used by the UART connected to the interface MCU. For more information, see section Virtual COM port.

Try changing CTS and RTS as well. If that does not work then you probably need to turn off any logging. 

[kevin seo]

I want to use pins 2,29 instead of pins 6 and 8.

I changed the cts and rts but it didn't work

[haakonsh]

I do not know myself, it might be ESD damage to those pins. You can check for ESD damage by toggling the pin and monitor it with an oscilloscope. A pin with blown ESD fuses will behave very strange. 

It could also be that those pins are a bit too capacitively loaded, if that's the case you need to set the GPIO drive strength to high for those pins. See nrf_gpio_cfg and nrf_gpio_pin_drive_t. The high drive strength option is called NRF_GPIO_PIN_H0H1.

[kevin seo]

I have 3 nrf52840DK boards. but everything didn't work...

[kevin seo]

In the radio test example, uart works well with pins 2 and 29. However, it does not work in direct test mode.

[haakonsh]

"However, it does not work in direct test mode."
What are the symptoms?

[kevin seo]

I'm solved this problem!

I made mistake.

Thank you.