I talk about this board https://www.banggood.com/it/Micro-F3-Flight-Controller-Board-Buited-In-DSM-FLYSKY-FRSKY-Receiver-For-Eachine-E010S-p-1131611.html
today is arrived my second board same stuff and same problem of my first one
no way to connect to betaflight and flash firmware
really the board is very good in flight also with it's firmware preinstalled, but if you want to flash it to a new upgraded version the response is bootloader connection failed i have tried everything but I'm quiet sure there's not other way
ok.. the solution:
all this better before build your whoop, with motor disconnected and the board in hand.
Provided stm32 drivers and serial port are ready (you find instruction on wecome BF/CF page)
check on BF/CF com ports available (not com1)
ok all installed properly you can try to connect and using BF/CF flash utility but if your board is like mine you see that not work.
download and install ST DEMONSTRATOR FLASHER-STM32 http://www.st.com/en/development-tools/flasher-stm32.html
soldering together boot pins, you find it under the two yellow condensers just on bottom the white boot write
download your firmware, I suggest betaflight_3.1.5_SPRACINGF3.hex BF version you find here https://github.com/betaflight/betaflight/releases
3.1.7 got gyro problems at the moment. also 3.1.6 work well.
connect board to usb and start st demonstrator if properly connected to com ports you see a traffic light symbol allow target readable, next the page and nothing to do, target is automatic.. next page again to upload firmware page, dot download to device, select Firmware from your pc .HEX file type and load it. wait blue bar become green, close the program. here demonstrator guide
desoldering boot pins before connect to BF/CF
open the program, connect (without motors connected) go on configuration menu and set motor to brushed, save..
srtart build your whoop, bind it and finsh to setup all features on BF/CF..