To enable the ADC’s we need to edit
/boot/uboot/uEnv.txt to include the
GB-ADC.dtbo overlay. . There is some very good documentation availble about using and testing the ADC below.
Make sure to uncomment the line
enable_uboot_overlays=1 this allows overlays to load on boot:
# enable u-boot overlays enable_uboot_overlays=1
Then you can add the line GB-ADC.dtbo to one of the pre-existing slots.