import serial, time
Switch from a USB 3.0 (blue) port to a USB 2.0 port , as many flashing tools struggle with the high-speed protocols of 3.0 ports. 3. Verify Connection Timing handshaking... error unexpected response 0x68
stm32flash tool reported: handshaking... error unexpected response 0x68 . Analysis: The STM32 was not in bootloader mode (BOOT0 pin low). Instead, it was running user application code that was printing lowercase 'h' repeatedly in a loop. Fix: Pulled BOOT0 high and reset the chip. The bootloader responded with 0x79 (ACK), and programming succeeded. import serial, time Switch from a USB 3
The first two packets whisked across the fiber-optic umbilical. SYN . SYN-ACK . Then, the return payload. error unexpected response 0x68
So if your device expected 0x06 (ACK – Acknowledge) or 0x15 (NAK – Negative Acknowledge) and instead received 0x68 , the protocol is broken. Your device is basically screaming: "I asked if you were ready, and you replied with the letter 'h' – I have no idea what to do with that."