That is a tough one. It was difficult for me to even get the outsput schematic on the voice HAT to control hardware. Working with a guy named Shabazz eventually figured out a presumptive mosFET circuit google must be using. The best teardown guide I have seen is here: http://hackaday.com/2017/05/30/diy-google-aiy/ with some more history on the outputs here: https://www.element14.com/community/community/raspberry-pi/b...