Nrf52 adc sample ground

[Fennec]

Is there a way to sample VSS with the adc? It seems as if an input channel can only have an AIN pin or VDD as an input.

[Fennec]

No answers/knowledge from anybody on this subject?

If I figure it out on my own I will post a solution here. Best I can think of is pulling the AIN pin low and sampling that. My main goal is to drain the adc capacitor by sampling ground. Other micros seem to support sampling ground internally, as far as I can see the nrf52 only supports sampling from VDD.