Unused GPIO Pins

[Imran]

Hello,

What should I do with unused GPIO pins on the nRF51822?

Imran

[Håkon Alseth]

Hi Imran,

The default behavior of unused GPIOs (it's reset value) is set as input, with an internal switch (NRF_GPIO->PIN_CNF[], bit 1) set to disconnect. This is the recommended configuration of unused GPIOs to ensure that they do not draw current due to floating inputs.

So, just keep the unused pins un-connected on your custom PCB and make sure that these pins have the reset value of NRF_GPIO->PIN_CNF[].

Cheers, Håkon

[Imran]

So the pin is kept floating on the PCB but the internal switch is disconnected?

[Håkon Alseth]

Yes, that is correct.

[sort]

Hi, Alseth,

I am very concerned about ESD ( 8KV/15KV for contact/air respectivelly) in my project. For the unused GPIO pins, do I need to add TVS diode or pull-resistor to the GND?

[annapalu]

Hi Hakon,

i have set the internal switch of unsed pin to 1 ( disconnect). But if i measure the the voltage on the pin, for some of them is 3 V for the other 0. is it normal?

Thanks.