[clug] USB ADSL2+ modem?

Bob Edwards bob at cs.anu.edu.au
Tue Dec 20 04:08:56 UTC 2016

On 20/12/16 13:55, Luke Mewburn wrote:
> On Tue, Dec 20, 2016 at 12:13:55PM +1100, Bob Edwards wrote:
>   | I realise that ADSL/ADSL2/ADSL2+ has higher voltage requirements
>   | than can generally be met by USB/USB2/USB3, but not sure if that
>   | isn't a solvable problem that might already have been solved?
>   |
>   | I can't find anything on the interwebs that gives me much encouragement.
>   |
>   | Ideally, I would like to power my (bare/bridge) ADSL2+ modem from
>   | my laptop's power supply/battery and the obvious way to do that would
>   | be to use a USB-based modem.
>   |
>   | My (Linux) laptop would then do the rest and I can (trivially?) keep
>   | it patched etc. and keep a closer eye on what is really going back and
>   | forth on the ADSL connection...
>   |
>   | Anybody got any thoughts or recommendations?
>   |
>   | cheers,
>   |
>   | Bob Edwards.
> Hi Bob,
> I notice that one of the ADSL modems I have (the TP-Link TD-8840T)
> has a power rating of 9V @ 0.6A (540mA), and 4 ethernet ports.
> I found this link on adafruit, which is 9V @ 500mA:
> 	https://www.adafruit.com/product/2777
> It may be sufficient given the router may not need the full 540mA
> if only using 1 ethernet port.
> cheers,
> Luke.

Hi Luke,

Interesting idea. A USB3 port should be able to do up to 900mA @ 5V,
so the 500mA @ 9V into the modem/router looks sort of feasible
(although it requires an unlikely 100% conversion efficiency...).

I wonder how much of the 540mA (@ 9V) is for the ADSL sub-system, and
how much is for the internal CPU, memory, ethernet port, ethernet
switch, power conversion etc...

If I could find a solution without the ethernet switch, router etc.,
I might get closer to the power budget of USB2 (2.5W).


Bob Edwards.

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