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Hacking Qualcomm With Just A Few Resistors

About the project

Following Shahariar Hossain's project on hacking qualcomm with a ATtiny85, I took his advice to just try it with resistors.

Project info

Difficulty: Easy

Platforms: Electric ImpQualcomm

Estimated time: 1 hour

License: GNU General Public License, version 3 or later (GPL3+)

Items used in this project

Hardware components

Resistor Resistor x 4
Switch any Switch any x 1

Hand tools and fabrication machines

Soldering iron Soldering iron x 1

Story

I have got a nice powerbank with QC 3.0 support. Only a switch to change to different voltage is missing.So I searched for information how to change the voltage and found Shahariar's project, see: https://www.electromaker.io/project/view/hacking-qualcomm-quick-charge-qc-2030-with-attiny85 

I followed his hint to just try it without a microcontroller. The thing is, you have to create two voltage on the USB Data lines D+, D-, to change the output voltage.

D+     D-        Output0.6V  0.6V    12V3.3V  0.6V       9V3.3V  3.3V    20V0.6V  Gnd       5V (default)

I needed 12 V, so 0.6V on each Data line. Shahariar used 3.3V (mainly for the microcontroller) generated by a regulator. He got 0.6V from a voltage divider with two resistors. My idea was just to use the 5V from the USB power and also a voltage divider. I like it short and simple, so my approach was to take around the same current as Shariar in his project: 3.3V / 12.2kOhm = 0.27mA not  so much current.

The resistance for my voltage divider is: 5V / 0.27mA = 18kOhm. The current in a voltage divider is the same in both resistors, the first resistor is therefore 0.6V / 0.27mA =  2.2kOhm. The second one, arithmetical ~ 16kOhm, I choosed 15kOhm.

This is the wiring scheme:

As you can see in my project picture, this approach works perfect at least for 12V. Even with 20V the voltage divider consumes only 11mA.

Just plug-in the voltage divider arrangement, the Switch position is not important, either on or off. First you get 5V, because you have to init the QC handling, just wait 2-3 sec and press the switch. If you get 12V, great. Otherwise wait 2-3 sec and press the switch again, now you should get the 12V.

Credits

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