How to set the GPIO of NRF52840 to high resistance state？

[wanwandeyueliang]

I want to set the GPIO of NRF52840 to the high resistance state. How do I set the GPIO of NRF52840 to the high resistance state,  please help me,thanks!

[wanwandeyueliang]

You're right. I'm using a UART peripheral, In fact, the 52840 on the circuit board is connected to a Bluetooth module through a serial port. For faster debugging of the Bluetooth module, the serial port terminal is used to directly communicate with the Bluetooth module. Therefore, I want to set the serial port of 52840 to a high resistance state, that is also high Z. This is what I set up in the program, 

But it didn't seem to work, how do I set it? 

[Edvin]

Still not sure what SDK you are using, but I will assume it is the nRF5 SDK until you say otherwise. 

If you initialized the UART using APP_UART_FIFO_INIT() or app_uart_init(), try to uninit the UART first using app_uart_close().

If you used another way to initialize the UART, then see if the file that implemented the init function has an equivalent uninit function. 

As you can see in app_uart_close() -> nrfx_uarte_uninit(), it will first disable the uart, and then set the pins to the default state:

I am not sure how the UART drivers would behave if you try to take it's gpios while it is active. 

Best regards,

Edvin