Ok I figured my problem out. The ripple from the circuit will trigger the USART1 RX pin to make it enter serial mode. by pulling the PA10 up to prevent accidental triggering, It can finally enumerate normally.the dmesg -w report
I have some clue here.But the solution is temporally.The chip and board for me is stm32f411ec6on the Blackpill board.I have to touch the digital pin with fingers while the USB DFU boot loaders begin. If I don't do it. The 25 Mhz clock will show up fo...