so ive been flying whoops for like a year and finally decided to go for a proper 5inch freestyle build. got a apex hd frame, ran55 motors, and picked up a 45amp 4in1 ESC stack from a buddy who was selling off his parts. problem is i cant figure out which pads are which on the ESC board, the silkscreen is basically rubbed off on half of it and the original manufacturer sticker is gone so i dont even know what brand it is.

ive been trying to match it to pinouts online but nothing looks right. the main power pads i think i can figure out but theres a row of smaller pads on one side that i have no clue about. current sensor? uart? i really dont wanna just start soldering random things and fry it before i even fly it.

anyone dealt with this before or know how to identify an ESC from just looking at the board? theres some markings near the MCU chip if that helps, says STM32F051 on it

the STM32F051 marking will narrow it down quite a bit actually. that chip got used on a bunch of mid-range 4in1s around 2020-, mostly iflight and a few speedybee variants. if you can post a photo of the board i can probably tell you exactly what it is, ive got a folder of ESC pinout pics i've collected over the years because i keep running into this exact problem with used parts.

also for the smaller pads, on most of those boards the row along the short edge is usually telemetry, current sensor output, and sometimes a 5v or 10v BEC tap. dont solder anything to that row until you know for sure, you can run the build fine without current sensing anyway if you just leave it unconnected for now. get it flying first then sort out the extras

yeah post pics definitely. also random tip, if you shine a bright phone flashlight at an angle across the board sometimes you can read the silkscreen even when it looks gone, the texture is still there it just needs the right light. saved me a couple times when i got sketchy secondhand gear