I don't know how to handle not-use pins for safety.

[makoto]

There are 31 io pins on nRF51822. I use 8 io pins for our product. But I don't use the other pins.

All of io pins have the same default value after reset as follows.

・Configure pin as an input pin ・Disconnect input buffer ・No pull

In many cases , it is necessary for circuit's safety that the input pins have to be fixed their logic level(H or L) by using external or internal pull up/pull down registers.

In this case what should I do for the not-use pins. If I do nothing for not-use pins (I mean they hace no external or internal pull up/pull down registers), what troubles will happen?

[Hung Bui]

Hi Makoto,

The un-used pin when configured as in reset state: "Configure pin as an input pin ・Disconnect input buffer ・No pull" is disconnected from the inside. I don't think you would have any trouble leaving it like that. But you can of course connect them to GND if you want.