An USB isolator helps remove floor loops and minimizes electromagnetic interference (EMI) involving the computer along with the related unit. 1x GND 3V3 (P2 with 2 pins two.54mm) connector can be used to electricity externally the WCH CH569 MCU (it is usually recommended to remove the P4/SHUNT in that scenario https://kameronnfwne.wikibuysell.com/1274451/the_definitive_guide_to_hydrabus