Handshaking... Error Unexpected Response 0x68

Here is your cheat sheet for resolving the 0x68 error, ranked from most to least likely.

| Priority | Action | Success Rate | | :--- | :--- | :--- | | 1 | 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% |

Enabling detailed logging on both the client and server can help diagnose the issue. Look for logs that provide details about the handshake process and where it fails. handshaking... error unexpected response 0x68

Handshaking is the initial process two devices use to establish that they are ready to communicate. It’s the digital equivalent of two people agreeing on a language before speaking. There are two primary types:

The error occurs during this setup phase. The master device (e.g., your PC) initiated a handshake, but what it received back was nonsensical. Here is your cheat sheet for resolving the

Embedded devices often enter a bootloader on startup, expecting a specific "magic byte" sequence (e.g., 0x7F for STM32, or 0x55 for Arduino). If the host sends the wrong byte due to a script error, the bootloader might reply with an error code.

When you see "handshaking... error unexpected response 0x68", do not reboot everything randomly. Follow this forensic process. The error occurs during this setup phase

Standard RS-232 uses +12V for logic 0 (space) and -12V for logic 1 (mark). TTL serial (common on Arduino, ESP32) uses 0V for logic 0 and 3.3V/5V for logic 1.

If you connect a TTL device to an RS-232 port without a level shifter:

However, sometimes the receiving UART will interpret the voltage margin incorrectly, generating random bytes like 0x68 during the start-bit sampling.