Error Unexpected Response 0x68 - Handshaking...

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.

If you are working with IoT modules like the SIM800, SIM7000, or SIM7600 series, you may have encountered the following cryptic message in your serial debug log:

prepare article for handshaking... error unexpected response 0x68

This error usually occurs during the initial "handshake" phase—the moment your microcontroller (MCU) tries to establish communication with the GSM/LTE module. It indicates a fundamental failure in the Serial Communication (UART) setup.

This article breaks down why this happens and how to fix it.

If you are testing the module on a breadboard or with loose jumper wires:

The 0x68 error rarely indicates a hardware apocalypse. Instead, it points to a mismatch of expectations. Here are the five most common scenarios. handshaking... error unexpected response 0x68

The error "Unexpected response 0x68" is rarely a fatal hardware failure. It is almost certainly a configuration mismatch.

Immediate Action: Adjust the host baud rate to 9600 or 115200 and retry. If the error persists, update the host code to recognize 0x68 as a valid start-of-frame.

Understanding the "Handshaking... Error Unexpected Response 0x68" If you are working with mobile device servicing tools (like UnlockTool ) and encounter the message "Handshaking... Error Unexpected Response 0x68,"

you have likely hit a common communication wall between your computer and the device’s chipset.

This error code typically surfaces during the initial "handshake" phase, where the software attempts to establish a secure link with a device in MTK (MediaTek) EDL (Emergency Download) mode. A response of

usually indicates that the device's bootloader or security hardware rejected the initial command or sent back data the software didn't expect. Common Causes for Error 0x68

The handshake is a delicate process where protocol versions and security keys are exchanged. When it fails with this specific code, the culprit is usually one of the following: Driver Conflicts: Handshaking is the initial process two devices use

This is the most frequent cause. If the wrong USB drivers (e.g., generic Windows drivers vs. specialized MTK/LibUSB drivers) are active, the software cannot interpret the device's response correctly. Security Patches:

Modern devices with updated security patches often block the standard exploits used by servicing tools. The

response may be the device saying "I don't recognize this command." USB Port or Cable Quality:

Unstable data transmission can corrupt the handshake packet. SERIOUS servicing often requires a high-quality, high-speed cable and a direct connection to a motherboard port (avoiding USB hubs). Incorrect Model Selection:

Selecting the wrong CPU or model in your software can lead to the tool sending instructions that the hardware cannot process. How to Fix Handshake Error 0x68 Reinstall LibUSB Filters: Many tools like UnlockTool

require the "LibUSB Win32" filter to be installed specifically for the "MediaTek USB Port" or "Preloader" device. Use the filter wizard to uninstall and then re-filter the device while it is connected in the error state. Use "Disable Auth" (MTK):

If you are working on an MTK device, ensure you are using the "Disable Auth" (Bypass) feature before attempting the main operation. This clears the security hurdle that often triggers unexpected responses. Check Device Manager: The error occurs during this setup phase

Open Windows Device Manager and watch the "Ports (COM & LPT)" section. When you connect the device, it should appear as a specific port (e.g., MediaTek USB Port Qualcomm HS-USB QDLoader 9008

). If it appears as "Unknown Device" or has a yellow triangle, your drivers are the primary issue. Try a Different Connection Method: Switch from a USB 3.0 (blue) port to a USB 2.0 port

Change the cable to an original or high-grade aftermarket data cable.

Restart the software and perform a "Force Restart" on the phone (usually by holding Power + Volume Down) while it's plugged in. Technical Summary

The handshake is the "digital greeting" between your PC and the phone. When the phone sends

instead of a "Hello," it’s essentially a protocol mismatch. By ensuring your drivers are clean and your hardware connection is solid, you can usually bypass this error and proceed with your device repair or unlock.

For more specific troubleshooting, you can refer to the official guides from tools like UnlockTool Support Sectigo's technical blog for general handshake theory. phone model

Temporarily set flow control to "None" in your terminal application. If the error disappears, the problem is flow control mismanagement.