[USB3-HUB7BC] Slow Charging


#1

If I plug the hub into the power supply, my Samsung Galaxy S5 will charge at upwards of 1A, and my Amazon Fire HD 8 (6th generation) will charge at upwards of 0.8A. (And, the Fire HD will not complain about being attached to a low power charger.)

However, if I connect the USB hub to my Linux Desktop (Ubuntu 16.04, kernel 4.4.0-93-generic), both devices charge at only ~0.5A, as measured by an inline USB power meter. [1] And, the tablet complains about being connected to a low-power charger whether or not it’s attached via the power meter.

I’ve been contemplating what the problem could be, since almost everything is relatively new and unknown to me in this setup. I was curious if the linux kernel would handle power negotiation in this case, and thus could possibly be a driver issue; but I was informed by a Linux USB driver expert that the kernel does no such thing, so the problem would have to be with the hub and/or devices. Not sure what charging profile(s) my devices support, but your website says this hub supports both the Galaxy S4 and Kindle Fire 8.9, [2] earlier products marketed under the same model name.

[1] https://www.amazon.com/gp/product/B01…is the power meter I have. Not sure how accurate it is, or if it could possibly introduce any power negotiation problems (I was disappointed it didn’t have USB 3.0 pass through), but I am reasonably confident in this device at this point.

[2] http://plugable.com/products/usb3-hub…


#2

Hello Leon,

Thank you for contacting Plugable support! Sorry to hear about this issue. I’d be more than happy to assist you.

Just to rule Linux out as the cause - do you have access to any Windows or Mac systems where we know BC1.2 functionality to work as expected?

It’s also possible that while your devices are newer than the ones that we tested, they may lack BC1.2 support to charge at greater than 500mA when connected to a host system. Though this seems unlikely.

Please don’t hesitate to let us know of other questions.

Thanks again for contacting Plugable support and best wishes!

Joshua Henry
Plugable Technologies


#3

Unfortunately, all the Windows systems I have easy access to are old enough that they only have USB 2. Even though the hub is incapable of passing usb2 data to a usb2 host computer, connecting it to a usb2 host port still slows the charging down to 0.5A.

It would _seem_ as though your hub supports the S5 and Fire HD 8 charging profiles, because it does work adequately well when there is no host connection. And I would have guessed that the hub takes over power negotiation, but consulted with somebody more knowledgeable just to make sure. I’m hardly an expert in this area, but I shouldn’t have to be to have a working product.

Also, I’m pretty confident the expert I referred to is correct. I’d rather not publicly associate their name with this issue, but they are very well known in the Linux kernel community and work directly with USB kernel drivers.

And, you do advertise this product to work with Linux, so I’m hardly using it outside the advertised parameters.


#4

Hi Leon,

I doubt Linux is causing the issue, and we do support Linux, but I figured Windows was a good thing to check against as we have seen times where Linux Kernel updates do break hub support, sometimes quite badly.

“Even though the hub is incapable of passing usb2 data to a usb2 host computer, connecting it to a usb2 host port still slows the charging down to 0.5A.”

The hub should work fine on a USB 2.0 system for USB 1.1, 2.0, and 3.0 devices.

“It would _seem_ as though your hub supports the S5 and Fire HD 8 charging profiles, because it does work adequately well when there is no host connection.”

These are different than when connected to a host. When connected to a host those profiles are disabled as they do not allow data transfer, instead when on a host the BC1.2 profile is engaged. Which is why I am curious if perhaps they are not BC1.2 compatible devices.

Thanks,
Josh


#5