@Majenko says in the leading (19 Upvote) answer here not to use VIN and USB socket at the same time.
You must never ever connect VIN to a power source and connect the USB socket. That can destroy the USB port in your computer. There is zero back-powering protection on [LoLin v3 board] board.
I need to do diagnostics on my Wemos (LOLIN) D1 R2 V2.1.0 while it's connected via 9-12V barrel jack and the Vin pin connected to an L9110H H-bridge as an output (bridge input).
Does the Wemos (LOLIN) D1 R2 V2.1.0 (ESP8266) work like this as well? Would I be able to run diagnosics with Serial through my USB socket while running this setup?