This document created at Jan 9, 2023, 3:54:58 PM and modified at Jan 23, 2023, 3:43:31 PM.
Certain Huawei models at certain firmware level need a so-called Harmony Cable if you want to access the phone in factory mode.
Using Chimera and the Dynamic Harmony Cable you will be able to handle the PC-phone communication without removing and reinserting the USB cable. This will save you time during the procedure, it also reduces errors due to forgotten or wrongly executed cable insertion.
Instead of buying expensive devices, there is an option to buy and modify an inexpensive board. It’s a special type of USB HUB + CH340T USB serial chip. We expect that some hardware shops will soon offer it as a ready-to-use product, but until then you can follow these instructions to create your own:
Necessary parts and tools
• A USB HUB + serial port device designed for Raspberry Pi (like THIS one)
• 1.5K Ohm resistor
• A piece of wire
• Sharp knife
• Soldering iron
• Proper size of tip
Preliminary inspection of the device
Before you proceed with the required modifications you should inspect it, follow the steps below to make sure you have the correct device:
• If you connect it to PC using its back side connector, a new USB HUB should appear in Windows Device Manager
• If you connect the UART port to the HUB using a second cable, a CH340 serial port should appear in Device Manager
If it works like this, you can disconnect the device and start modifying it!
Modification of the device
There are 4 main steps that you need to follow to have a working Dynamic Harmony Cable.
1. Remove the second resistor shown in the picture below
2. Make a connection from the right side of the TXD LED to USB4 D+ line (second from the top)
3. Make connection with the resistor from the right side of the removed resistor to CH340T chip pin 15 - sixth pin from the top, at right side
4. Kill this via-connection. Cut it with a scalpel or drill over it.
You are done, after the modifications you should have a device like this:
Test your modifications
• Connect a micro USB - USB A cable between UART and (unmodified) USB 1
• Connect a Huawei phone in a bricked state to USB 4
• Connect your PC using a micro USB - USB A cable to the connector marked as USB HUB - back side of the board
This setup can function as an original Harmony cable. The LED will light up showing that the cable is in Harmony mode now.
If everything is working fine and you have the latest Chimera supporting this "Dynamic Harmony Cable", Chimera will recognize your device and asks you about using it when you start a procedure that might require a Harmony cable.
Hoping that you have no other CH340T UART connected to your PC, Chimera will be able to find this UART device connected to the USB 1 port of the hub and will be able to set and remove Harmony function from your cable without asking you to remove and reinsert the cable. The LED will show the actual state of the cable (Harmony: light on, USB2.0 HS - 480 Mbit speed: no light).
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