1. zejulio's Avatar
    need to enable fast charge/AC on USB and keep it enable to communicate via USB. I need my tablet to charge as connected to AC and be able to transfer files in the same way as if I connect to a PC.

    I will have a AC adapter in the middle powering the device 5V/2A, so I wont burn my PC USB port (I wont drain any power from the PC, just the D+/D-/GND Lines...). I know that I should not connect the tablet directly to a PC once I do this.

    I have my device rooted, but I do not want to use a custom kernel. Is there anything I can change on my kernel to do this?

    Once I think I saw some change that I must do in a system file to be able to do this, but I'm unable to find it now...

    Thanks for any tip,

    12-18-2014 04:00 PM
  2. Rukbat's Avatar
    It's not the kernel, it's the hardware. You need a Y cable that has one port for the phone, one for the computer and one for a charger to charge the phone. (Most Y cables are phone, OTG [like an external drive] and power for the OTG side.)

    If you connect the charger to the computer's 5 volt line, something's going to blow - the charger, the USB port, the USB chipset or the computer's PSU. The odds of it working without damaging something ... look in a trash bin for next week's winning Powerball ticket. Your odds are better.

    I don't know why you don't want to "drain power" from the PC - it's designed to handle the drain. (BTW, you don't want D+/D-/Gnd. D+/D- is a differential signal, it's not referenced to ground. If you connect the grounds you could cause a ground loop, which would cause enough noise that the phone wouldn't work properly - and the data connection might not also. You're introducing some differential mode noise - which USB is designed to not be susceptible to because the power is flowing over lines parallel to the data lines, making the noise common mode. There's a reason for just about every part of the cellphone - they didn't arrive at these designs by flipping coins.)
    12-18-2014 04:13 PM
  3. zejulio's Avatar
    Hello Rukbat,

    As I tried to explain, I do not want to drain power from the PCB USB port cause I want it do "Fast charge", to do this it must drain over 1Amp to charge.
    As you know, normal USB Ports should not drain more than 0,5A.

    I need my tablet to be always ON. If I do it with 0,5A charging the battery will run out and the tablet will power off.
    So I must use an external power supply capable of more than 0,5A, so I can charge the battery while working.
    If I do not need any connection I could shunt D+/D- and it will charge, but I need to exchange data in D+/D-.
    This tablet is not compatible with BC1.x CDP (Charging Downstream Port).
    Shunting D+/D- the tablet will charge at 1,5A, so the hardware is capable of this.

    All I need is to mix this, charge at 1,5A and also communicate with D+/D-...

    I have tried some charging emulators with CDP, with several profiles, but I was unable to make it work. I can make it drain the 1,5A but once I connect someting to D+/D- it will lower back to 0,5A...

    I'm shure that's a software hack for this, I just did not find it yet...
    Also I do not know where can I get a kernel with fast-charge option for my device, since it's chinese...


    12-18-2014 07:01 PM
  4. zejulio's Avatar
    After all this years, still looking for answer on this...

    06-08-2016 06:21 PM

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