我用STM32F105RB UART1 ISP 可以下载 另外:
If USART1 is used to connect to the bootloader: the USART2_RX (PD6),
CAN2_RX (PB5), OTG_FS_DM (PA11) and OTG_FS_DP (PA12) pins have to be
kept at a high or low level and must not be left floating during the detection phase