nrf21540 PDN default or high impedance state

[Namklak]

Connecting nrf21540 to a nrf52840.   840 GPIO default state is input, input buffer connected.  One of the 840 GPIO pins is connected to the 540 PDN pin.

1) If the 840 gets stuck in the bootloader before the GPIO to the 540 PDN pin is configured, what state will the 540 PDN pin be in?  Clarifying, the 840 GPIO pin will not be driving the 540 PDN pin.

2) If the 840 resets while its GPIO is driving the 540 PDN pin high (so the 840 will no longer be driving the 540 PDN pin), will the 540 PDN pin drift low, disabling the 540?

Thanks,

Bob

[Priyanka]

Hi Bob,

Please take a look at this ticket.

You can see that the GPIO has a default input state with inout buffer connected and no pull-up or pull-down enabled (unless you explicitly do this). So if stuck in the bootloader state, the GPIO pin is in high impedance state and so the PDN will be left floating and there is no specific state which it will be in. It can say, pick up noise etc and maybe go to some undefined state. So if you need it to go to a specifc defined state in such conditions, you can use some kind of external pull-up or pull-down method.

Also, when the nRF52840 resets, again, the GPIO will go back to it's default state and it will no longer drive the PDN high. The same thing as mentioned earlier happens, i.e. PDN is left floating unless specified by an external pull-up or pull-down in such conditions.

Regards,

Priyanka