Edit:

It charges devices on its own If I first plug it into a computer or android device and then plug it into the device I want to charge

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[–] 31 points 1 year ago (6 children)

Becase some devices require a signal on their comm pins to negotiate the correct voltage to charge the device. Also some devices are dicks and needs a proprietary signal in order for it to charge. Looking at you sony.

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  • [–] 12 points 1 year ago (4 children)

    Sony and proprietary nonsense, name a more iconic duo

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  • [–] [S] 1 point 1 year ago

    Becase some devices require a signal on their comm pins to negotiate the correct voltage to charge the device.

    Whats weird is that my usb c wall powered hub will charge devices on its own if I plug it into a computer (or sometimes an android phone) first and then unplug it and plug it into the device I want to charge

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  • [–] 9 points 1 year ago* (last edited 1 year ago) (1 child)

    The hub doesn't have a negotiation chip to set the voltage correctly. It is likely presenting as a bus hub. Like if you do $ lsusb on Linux, you'll see the hub and whatever is connected. That hub may be integrated into other chips or it may be stand alone as a peripheral somewhere on the board. It is basically like a digital cable splitter for the bus. It is only concerned with the data. The power is likely just passed through. For USB-C PD, it would need some complex additional circuitry to negotiate, convert voltages and do current limiting. The way the pins can be inverted by flipping the connector makes it logically complicated.

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  • [–] 5 points 1 year ago*

    Speaking of passing through PD communications, I have a cheap Chinese power meter that sort of does that but not properly. Hopefully, OP has a good hub that plays nice.

    If you use a setup with a power supply, first cable, power meter, and a second cable, you can measure things when connected to a chargeable device like a laptop. It obviously tells the PS to give it 12 V, which it will. Once you unplug the laptop from the second cable, the voltage reading doesn’t drop back to 5 V. Apparently, the power meter doesn’t let the PS know there’s no load anymore.

    As a result, you get a USB-C cable that gives you 12 V without asking any questions. Guess what happens when you plug in something that can only handle 5 V? Bad things. Don’t ask me how I know.

    Anyway, once you unplug the power meter from the first cable, the PS finally gets the message and drops the voltage back to 5 V. Makes me wonder if a hub could behave the same way as my power meter.

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  • [–] 7 points 1 year ago

    I'm guessing the driver on the PC regulates the power somehow and not any logic on the hub itself.

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