The BootROM relies on stable voltage flowing through the motherboard. If the battery is completely dead, severely degraded, or fluctuating in voltage, the phone will fail to maintain its connection to the PC during the handshake process. Step-by-Step Troubleshooting Guide
If you receive an unexpected byte (like 0x68 ), don’t fail immediately. Instead:
A faulty USB cable or port providing unstable power or data. 2. Verify MTK USB Drivers handshaking error unexpected response 0x68
ISO/IEC 7816 communication mismatches where the Answer to Reset (ATR) frame yields malformed status bytes.
On some devices, the battery must be disconnected and reconnected to force a fresh BROM state. 5. Troubleshooting Summary Checklist Potential Cause Driver Mismatch Reinstall MTK VCOM Drivers. Locked Bootrom Use an Auth Bypass utility. Wrong Boot Key The BootROM relies on stable voltage flowing through
A very common manifestation of this error is during attempts to upload code to an ESP32 board. The upload tool will often report a "fatal error: Failed to connect to ESP32: Invalid head of packet (0x68)" message.
: Ensure the battery has sufficient charge (at least 30%). In some cases, a device stuck in a boot loop or with a corrupted partition (like rrecord ) can trigger this response. Instead: A faulty USB cable or port providing
Added a 470µF capacitor across the ESP8266’s power rails.
A bad handshake is frequently traced to LibUsb failing to filter the connection port.