Using digital GPIO pins to access analoge GPIO pins

[Tellef Goderstad Sunne]

Hi,

Is it possible to route an analoge signal through a digital GPIO pin to access the inner analoge pins of a nRF52840? I want to avoid using via-in-pad to keep the cost down.. For example if I want to use P0.03/AIN1 (B13), can I route through P1.15 (A14)?

BR,

Tellef

[haakonsh]

That should be fine as long as you do not configure the digital pin, default reset config is high impedance. 

The pin will add 3pF to your trace though so you should increase the acquisition time setting as if the source impedance is at least double what it normally would be. The acquisition time is dependent on how fast you can charge the internal sample-and-hold capacitor that is 3 or 4 pF itself. This means that you will need twice the current to charge it fast enough, given a doubling in capacitance. See Acquisition time. 

[Tellef Goderstad Sunne]

Thank you!