: Perform a hard reset or power-off/on. This can clear hung bootloader states that might be stuck sending initialization characters.
: If you are using a serial-to-USB converter, ensure no other background processes (like a system monitor or another terminal) are trying to access the same COM port.
Unplug the ribbon cables from both the control board and the affected hashboard.
If the error persists, you may need a custom bl2 or payload file specific to your chipset. 3. Change Tool/Payload handshaking error unexpected response 0x68
What , programming language , or hardware chip are you using? What operating system runs your environment? Does this happen every time or only intermittently ?
In the world of ISO 7816-4 APDU commands, the status word 68XX (where XX is a second byte providing more detail) is a specific indicator of a problem. According to older specifications, the range 68XX indicates that the "functions in CLA not supported," meaning the command's Class (CLA) byte was invalid or not supported by the card. A more modern interpretation, found within the NIST Biometric Evaluation Framework, defines CHECK_ERR_CLA_FUNCTION as 0x68 . If you receive an APDU response with SW1 = 0x68 , it signifies a problem with the command's CLA byte.
The value 0x68 (hexadecimal) translates to: : Perform a hard reset or power-off/on
The device has a high security level (SLA/DAA) enabled, and standard bypass payloads do not match the required signature.
: Ensure the serial/USB cable is secure. Poor contact can cause "ghost" characters like 0x68 to appear in the buffer.
When developing firmware on microcontrollers using serial interfaces, a 0x68 unexpected response implies text data or a synchronization echo is bleeding into your binary data stream. Unplug the ribbon cables from both the control
If all else fails, the issue might lie deep within your Windows registry, conflicting antivirus software, or an unstable USB controller on your motherboard. Attempting the entire process on a clean, secondary PC—preferably one running a fresh install of Windows 10 or Windows 11—often bypasses the software-level conflicts that cause the 0×68 error. Summary of Actionable Solutions
Ensure the phone battery is adequately charged and the device hardware is not damaged.