I saw that there is at least 2 pins (AIN6 and AIN7 as TP P25 and P24) wich does not seem to be connected to anywhere else; what should I do to make 2 additional voltage measurements to the program…
(As version B7.1 they are not further connected to anywhere else, but version B8 seems to have contacts to “Ruuvi-connector” P0.30 and P0.31 also, but if nothing connected to that, is it free for voltage measurements?)
The B8 P0.30 and P0.31 are free as long as nothing on Ruuvi Connector uses them.
You can take a look at ruuvi.drives.c NTC and photodiode drivers to see an example on how to use multiple ADC inputs in a program. Please note that radio interrupts may block the ADC and plan your program to fail graciously if ADC is unavailable for a while.