Double-check your connection strings. Ensure you did not accidentally prepend http:// to a host variable meant for a raw TCP or gRPC connection.
If the slave has a display, check for error codes. The 0x68 might be a generic "Communication Error" message generated by the slave itself, rather than a raw data error. handshaking... error unexpected response 0x68
Often, the phone's battery interferes with the flashing process, especially if the device is stuck in a boot loop. Double-check your connection strings
A device caught in a boot loop can spam the serial port with unreadable initialization codes. The 0x68 might be a generic "Communication Error"
Fixing the "handshaking... error unexpected response 0x68" Protocol Error
| Priority | Action | Success Rate | | :--- | :--- | :--- | | | Match baud rate, data bits (8), stop bits (1), and parity (None) – literally check every device. | 80% | | 2 | Disable flow control (XON/XOFF and RTS/CTS) in both software and hardware. | 10% | | 3 | Swap USB-to-Serial adapters – FTDI chips are more reliable than CH340 for handshaking. | 5% | | 4 | Check for signal inversion – Use a MAX232 level shifter for RS-232 to TTL conversion. | 3% | | 5 | Update or roll back serial drivers – Windows updates have broken handshaking before. | 1% | | 6 | Verify the peripheral is not in a fault state – Power cycle, check for stuck buttons (bootloader mode). | 1% |