USB Hub question

[Rubberducky]

Hi,

I've got a question about using a regular unpowered USB-Hub in the following manner:



The three-way cable between the power supply, the USB-out of the Pi and the USB-hub connects the power-pins of the hub's USB-input to the power pins of the power supply output and connects the data pins of the Pi's USB output to the data pins of the hub's USB-input.

This way:
1) The Pi is powered through the hub
2) Devices can be connected to the pi with their data pins, and the power will be drawn from the power supply

Am I making clear what I want to achieve?

Another question is: can, say a WiFi-dongle, draw it's power from a different source than the data? If not, this won't work of course.

[mrpi64]

are you saying that you are using a USB hub to power your pi, as well as connect devices for the pi to it?

[rpdom]

As long as the ground/0v lines of all devices are connected together they can take their 5v power from any supply.

Yes, your three-way cable will work to supply the hub, and the Pi via the hub, if you just connect the data wires and ground from the Pi USB output to the hub input and use a standard (good quality) USB to micro-USB cable to power the Pi.

[Rubberducky]

Hi,

Thanks for the answer.

So does this mean an unpowered USB-hub will just take the input power and and send it out of all ports on the USB hub? Or is there a limitation built into an unpowered hub?

are you saying that you are using a USB hub to power your pi, as well as connect devices for the pi to it?

If I understand your question correctly, this is what I'm trying to accoplish. I want to power the devices and the Pi from a single power supply, and I though this setup might to the trick.

[rpdom]

So does this mean an unpowered USB-hub will just take the input power and and send it out of all ports on the USB hub? Or is there a limitation built into an unpowered hub?

Yes. Most hubs, especially the basic ones, just connect the incoming USB power directly to all of the output sockets. They don't bother with any power management circuitry. Only the expensive ones with power supplies do that with on-board regulation.

[RaTTuS]

On one of my RPi's I power it from the powered USB hub and that also powered all the other things -
1 Plug to rule them all....

on another I power it all from an external HD case
1 Plug to rule them all....

[Rubberducky]

On one of my RPi's I power it from the powered USB hub and that also powered all the other things -
1 Plug to rule them all....

on another I power it all from an external HD case
1 Plug to rule them all....

Maybe I should look into a powered USB hub. Does anyone know of a powered USB hub that takes it's power from a USB-port?

That way I can just connect the powered USB-hub's data to the Pi, and the power input to a 2A USB power supply.

Edit: The reason I want a powered USB-hub that's powered through USB is because i'll be using a battery pack that outputs to a USB port, so all my power will come from this device.