External Sensors on Thingy:52

Good question!

So in terms of IO you have:

• IOEXT0/1/2/3 from the IO expander - good for digital IO, but not very fast as they go through the expander
  
• MOS1/2/3/4 - which control 4 MOSFETs for high power stuff
  
• D2/D3/D4 - analog capable IO from the MCU
  
  

On the rear of the thingy D2/D3/D4 are labelled as P0.02/etc.

So basically all you need is to use D2 3 or 4 exactly like you would on the Pico (analogRead(D2)) and you're sorted.