Some insight on WeDo 2.0 / Boost / Powered Up elements
The Powered Up connector
Mechanical characteristics, pinout and signal description.
The Powered Up serial link protocol
An overview of the dialog between Powered Up hubs and "intelligent" devices.
Power consumption of LEGO Bluetooth elements
What's inside WeDo 2 controller brick
You may also find related information in this Eurobricks thread.