How to set the GPIO pin input to no pull or float mode

[Alex.Guo]

Hi,

I am using NCS for development and configuring GPIO pin as input, but I found the GPIO can't configuring as NO-PULL mode. There are only two options: Pull up and Pull Down.

I can find the option NRF_GPIO_PIN_NOPULL in the SDK "nrf5_SDK_for_Mesh_v5.0.0" nrf_gpio.h file.

So how can I to configuring the GPIO pin as input in NO-PULL mode or Float mode on the NCS?

Thanks a lot

[Einar Thorsrud]

Hi,

Pull is configured by writing to the PULL field in the PIN_CNF register for a specific pin. If this field is 0, which is default, pull is disabled. So by default there is no need to do anything. If you have configured a pull, and want to disable it again, write 0 to this field.

Using Zephyr APIs, this means that to avoid using any pull, simply do not configure either pull up or pull down.

[Alex.Guo]

Hi Einar, 

Thank you for your reply.

I tried to modify the code in NCS, but it didn't work. Is there something wrong?

Thanks a lot!

[Einar Thorsrud]

Hi,

The code snippet you have here is from the implementation of dk_buttons_init() in nrf\lib\dk_buttons_and_leds\dk_buttons_and_leds.c, and the difference is that you have removed the flags that configure pull.

In what way does this not work?

Also, why do you want to remove pull from the input for this button handling code? Unless the input is always driven, which is typically not the case for buttons etc., then a pull resistor is needed. A floating input will cause problems.