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<div class="moz-cite-prefix">Phones a samsung galaxy s2<br>
<br>
USB power can be charging downstream ports (CDP - charge + data)
or dedicated charging ports (DCP - charge only)<br>
<br>
CDP "negotiate" (by software) a value - hence my problem as this
seems to be 96ma - one document talks of the charge current
corrupting data transfers which is a reason to limit it.<br>
DCP shorts two of the wires together and tells the usb port to
charge only. Docs are vague in what I have read so far but it
seems to default to 500ma in my case<br>
<br>
A further complication are other schemes to indicate extra current
capability - one phone I had use a 48k resistor across the data
pins (I think) which told the custom charger to release up to 2
amps.<br>
<br>
In my case, I have only CDP cables at work, software thats
negotiated 96ma but has charged at a higher rate in the past with
DCP cables.<br>
<br>
The fix: identify the usb bus/port and<br>
<br>
echo 1 >
/sys/devices/pci0000:00/0000:00:1a.7/usb1/1-3/bConfigurationValue<br>
or<br>
echo 1 >
/sys/devices/pci0000:00/0000:00:1a.7/usb1/bConfigurationValue<br>
<br>
(I did both) - a small shell/perl script will suffice to automate
it.<br>
<br>
Proof - it charged in a short amount of time instead of trickle
charging. No indication from lsusb that anything had changed
though so I guess its down to cutting up a usb cable so I can
insert a current meter into the path and confirm it.
Unfortunately I dont think the phone can tell me either. (default
samsung rom)<br>
<br>
BillK<br>
<br>
<br>
On 06/11/13 15:00, Pavel Volský wrote:<br>
</div>
<blockquote
cite="mid:CABOvRnKExJ7J_AzVjGu0gyxEU2bK-Z92x=zFy6GAu46C8o2F9Q@mail.gmail.com"
type="cite">
<p dir="ltr">Hello William, <br>
my first thought was - how can you be sure it is not the phone's
logic restricting the power allowed to the phone? <br>
On the other hand my second thought was - to shut up because i
know very little about this. But I really would like to know
more how you can measure and set this in Linux. </p>
<p dir="ltr">So, if you have any know-how resources, send me a
link please. </p>
<p dir="ltr">Ps - what kind of phone do you have? I can try some
tests on my SGS 3.</p>
<p dir="ltr">Pavel</p>
<div class="gmail_quote">On 6 Nov 2013 11:42, "William Kenworthy"
<<a moz-do-not-send="true" href="mailto:billk@iinet.net.au">billk@iinet.net.au</a>>
wrote:<br type="attribution">
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
I would like to override a USB hubs max power setting:<br>
<br>
I have a samsung phone that depending on the cable gets
enumerated and<br>
sets maMurdoch Searchx power from the usb hub (PC, Laptop
etc.) to 96ma.<br>
<br>
For some reason if it doesn't get enumerated it gets a
significantly<br>
faster charge rate (I suspect that it piggybacks an existing
connection<br>
that has already been negotiated to 500ma.) For practical
purposes it<br>
works well for this small subset of cables ... which is my
current dilemma.<br>
<br>
If I only have standard full function usb cables (4 wire,
independent<br>
earths) that enumerate fine, except they negotiate 96ma (less
than the<br>
100ma default if accurate!), can I override the negotiation
and set max<br>
power to 500ma? - note I am not trying to force 500ma current
draw but<br>
set the threshold to 500ma.<br>
<br>
OS is gentoo but hardware is either ASUS, Dell or Apple ...
same<br>
problem, same 96ma which supports the fact that more than this
current<br>
is really available if I can access it.<br>
<br>
BillK<br>
<br>
<br>
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</blockquote>
</div>
</blockquote>
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