NRF52840 GPIO default state

[Brennan]

Hi,

We would like to know the default state of the NRF52840’s GPIO pins - is it high, low or open?

The reason for this question – we need to know these pins’ behavior/state when the MCU is unpowered.

Thanks in advance,
Brennan

[awneil]

The default state applies when the chip is powered, but before the software has done anything to change it - this is not the same as the chip being unpowered!

As with any chip, you should not be applying signals to it when it isn't powered.

If you do apply signals to an unpowered chip, you get all sorts of weird effects due to power leaking "backwards" through protection circuits, etc...

[ketiljo]

Remember that max voltage on any GPIO is VDD + 0.3 V. Meaning that for an unpowered device, max GPIO voltage is 0.3 V.

[Brennan]

To add more context to my inquiry - one of the GPIOs is connected to another subsystem. There is a pull-up there but we'd like to know if the signal will be pulled down by an unpowered processor. While we have ensured that the NRF is powered up the entire time, we want to cover all scenarios as well.

[ketiljo]

Yes, the GPIO of a unpowered device will pull down. You have to make sure that the voltage on any GPIO doesn't exceed VD+0.3 V in all circumstances. Any voltage above this level will make the ESD protection diode conduct and you will backpower the device via teh GPIO.