NeonKey board fail to enter bootloader

Previously my neonkey board can enter to bootloader to flash binary from hikey960 with command “adb shell stm32_flash -u -d /dev/ttyAMA3 -e 0xffff -w /data/local/tmp/full.bin”.
but after flash another binary, my neonkey board cannot enter bootloader again after hold USR button and push RST button.
Is any other way to erase and flash the binary? or is there another way to enter into bootloader?

@weddy_wang_1 Did you try connecting BOOT0 to VDD (link JTAG pins 1 and 5 on P4 header)?

You can also use SWD debugger to flash/recover the board. More info here:

yes. I connect BOOT0 to VDD.
previously I can flash. but it does not work now after flash one binary.

Okay. Can you please paste the error log from stm32flash utility? Also, make sure that
the serial port (ttyAMA3) is not in use.

ttyAMA3 is available. the problem now is that when I hold usr button and push rst button, it will not go to bootloader mode again which is worked before.
I want to know how to flash erase and flash the binary in the situation that cannot enter into bootloader mode.
and not see the any uart log from ttyAMA3 port.
BTW, how stm32 st-link utility connect with neonkey board? is there other hardware dependency?

Yes, STLink utility requires the presence of STLink hardware which translates USB to JTAG commands. This needs to be bought separately since Neonkey has no on-board support for it. But Neonkey does exposes SWD debug ports, which you can use for connecting an external programmer like STLink. I personally use blackmagic debug probe for flashing/debugging.

I have one st-link, and it just connect to neonkey with SWIDO, SWCLK, GND, 1V8 pins.
but when try to connect in stm32 st-link Utility, it shows can not connect to target.
Did I connect the wrong pins or st-link does not support neonkey?

forgot to connect TVVC pin, it also needed.
neonkey can work with st-link now.