Hi Lluis,
I'm just saying there aren't 27°C in my room, and I don't need any external reference for that ...
I completely missed that Application Note, thanks for that. Now I have to understand what is the major source of heat in the board (the uP is N°1). I'm gonna go experimenting.... e.g. heavily duty cycling the uP to see if the read temperature settles to a different value compared to when the uP is simply wasting cycles....