How to use factory/bootrom mode service functions on Huawei devices with HarmonyOS

The Problem

Due to some changes done by Huawei, phones that are updated to HarmonyOS, would not present the Huawei USB COM 1.0 serial port after test pointing. Without the Huawei USB COM 1.0 serial port Chimera cannot communicate to these devices in factory/bootrom mode.

The Solution

You need to use a modified USB cable, we call it the "Harmony TP Cable". If this cable is used, Huawei USB COM 1.0 serial port is available and all Chimera factory/bootrom mode service functions will work on HarmonyOS models.

Harmony TP Cable, How-to

What you need:

  • 1 pc. 150 Ohm (150 Ω) resistor
  • 1 pc. 270 Ohm (270 Ω) resistor
  • 1 pc. 1.5 kiloohm (1.5 kΩ) resistor
  • and 1 pc. standard USB cable

Here is how-to make the cable:




Important Notes

  • You still have to test point (this cable only works if the test pointing is done)
  • Make sure that you always connect the cable to the phone first
  • Make sure, when asked to disconnect you always disconnect the cable from the computer first
  • You have to see the Huawei USB COM 1.0 serial port in Windows Device Manager. If you cannot see it, most probably the modified cable is wrong.

FAQ

Why do I see unknown device in Windows Device Manager?

Most probably you connected the cable to your computer first. Please make sure that you connect the cable to the phone first.

I disconnected the cable but I can still see the phone connected, why?

Most probably you disconnected the cable from the phone first, and not the computer. Please make sure that you always disconnect the cable from the computer first.

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