The minus power supply of the processor and the galvanically isolated circuits CANNOT be grounded, properly speaking zeroed or connected to the minus power supply.
Where did the "sick" erroneous interpretation of "EARTH" come from?
From old textbooks and laboratory circuits in which the battery minus was necessarily grounded in the electrical circuits of laboratory stands, this is not a mistake in this particular case, but the students decided for SOME reason that everything that minus the power supply is "EARTH", although no one gave them the right to call it that. This virus is transmitted by word of mouth and misleads engineers, and then leads to fundamental errors in the design of electronic devices.
