[Replicant] OTG hub with charging?

Fil fil.bergamo at riseup.net
Sun Jan 14 12:20:29 UTC 2018

On 13/01/2018 22:36, John Sullivan wrote:
> Hi all,

Hi John,

> Does anyone know of an OTG hub (ideally with 2-3 USB 2.0 or 3.0
> connections) that can charge the phone/tablet while the other devices
> are connected?

I just got myself one of those, featuring 3 usb connections and an
additional charging socket.
It also features a switch to change between charge and OTG mode, but
that seems to only apply to devices that actually separate the two things.
I obtained mixed results using it. Read on for more insight.

> I'm looking to use primarily with a Note 8.0 tablet, secondarily with a
> Note 2 phone if it so happens to work. Device wise, I want mainly to
> connect a USB keyboard and a USB wifi dongle.

I personally tried both of those devices with the OTB hub and this is
what I learned:
The fact is that OTG and charging need two different wiring
configurations (i guess micro resistors with different values are
involved), and while the cable itself can provide either of them at a
single time, the possibility to do OTG and charging at the same time is
device specific.
I think it has to do with the specific wiring *inside* the device.
My personal experience is that the Note 8.0 tablet happily charges while
using the WiFi dongle (had to do a couple of attempts with the
charge-OTG switch but it does work).
Unfortunately the Note 2 doesn't allow for such a configuration, no
matter what combination I tried. And I think there's absolutely NO
chance of having it charge while in OTG mode without changing resistors
on the board itself.

As a side note, the Galaxy S3 (GT-I9300) can also charge while in OTG
mode, just like the Note 8.0.

> I've read some commentary that seems to indicate that what I want
> doesn't exist for safety standard reasons (power only supposed to flow
> one way), but I can't tell for sure.

I tend to believe those are false claims..
Instead, as I said, it all depends on the specific device design.
And there's very little one can do if the device's board doesn't support
both modes at the same time..

Hope I've been helpful.

Happy hacking,


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