So I've seen a similar thread to this asking how to get 1.8A out of a single USB port. I've got so far as to know that this isn't possible.

But my question: How do I manipulate the communication between the USB device and the USB Host to make the host constantly put out 500mA? I know that it goes up in 100mA steps but without communication it also stays there. At 100mA.

What do I need this for? Well I'm trying to make my Pringles Speakers USB powered.

Has anyone out there got a solution at hand?

Best regards

EDIT: Well I guess it will be kinda helpful if I do add some more information.

The Pringles Speaker I'm trying to get USB powered usually runs with 3 AAA batteries at 4.5V. I am using a standard USB wire I had spare and did cut open. Attached everything they way it should be attached. When I now plug the USB cable into my USB slot the Speaker drains power. But it seems like the power isn't enough because the sounds emerging from the speaker are kind of... scratchy. They usually do sound the same when the batteries get low.

So I tried to plug in the speaker in my smartphone charger (5V at 1A). Then it worked like a charm.

Could the possible solution be to use a Y-cable?

  • \$\begingroup\$ A y cable can help. Same is done with usb hard drives \$\endgroup\$ – Passerby May 29 '14 at 22:05

90% of computers and laptops do not rate limit the USB port. It's connected to the 5V rail.

Another 9% have some sort of limiting only when more than 500mA is pulled.

The last 1% adhere to the full USB spec. Only allows 100mA until enumerated.

These are for regular USB ports. There is the USB battery charging spec for high powered ports that is different. The proper way is that you need a USB peripheral, like a microcontroller, that enumerates as a USB device requesting 1 to 5 blocks/units of power.

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  • \$\begingroup\$ Hey there! Thanks for the quick answer in the first place. Could I ask you some questions going further? \$\endgroup\$ – user43688 May 29 '14 at 15:20
  • \$\begingroup\$ I have noticed that USB ports connected to the extender pins on the motherboards usually have power issues, allot if not most of the times. But otherwise using the built in USB ports on PC's and Laptops works fine. I have made a few things draw roughly the suggested current and they work (expect on front panel USB) and have been working for 8+ months now. \$\endgroup\$ – Piotr Kula May 29 '14 at 15:21
  • \$\begingroup\$ In my experience my desktops include some form of current limiting and fault detection. \$\endgroup\$ – HL-SDK May 29 '14 at 15:21
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    \$\begingroup\$ A fourth group (of tablets and such like) will never allow more than 100mA, no matter how nicely you ask. \$\endgroup\$ – Spehro Pefhany May 29 '14 at 17:32
  • \$\begingroup\$ @user43688 like? \$\endgroup\$ – Passerby May 29 '14 at 22:01

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