Where can I find low speed USB cable? - Page 2

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Re: Where can I find low speed USB cable?
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Hey Juan, where in the spec did you find these numbers?  When I
browsed the thing all I found was the little 6.4.4 Prohibited Cable
Assemblies section but no detailed explanation of the capacitive
loading effect.

Another thing to note in that section of the spec is that they say
"long" high speed/full-speed cables exceed the capacitive loading of
low speed.  They don't make an attempt to define "long" so we're kinda
hung out to dry.  That is unless they go into greater depth somewhere
else in the spec or a peripheral document.

Re: Where can I find low speed USB cable?
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I guess this is a bit of a late reply, but I would say "long" is
anything that is longer than the max length of the low-speed cable.  I
belive the full-speed cables can be up to 5 meters or about 16 feet.
What is a short cable, 6 feet?  

--

Rick "rickman" Collins

snipped-for-privacy@XYarius.com
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Re: Where can I find low speed USB cable?
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I'm a little late chiming in on this, but thought I might point out
that yes, according to the USB spec, a low-speed cable must be
"captive," but captive is defined as either permanently attached to
the device or using a connector other than a standard USB connector
type to attach to the device. So a "captive" cable can be detachable
as long as it doesn't use the same connector as a full/high-speed
cable..

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I believe the main reason why low-speed devices aren't permitted to
use standard USB connectors is to prevent users from attaching cables
longer than 3 meters. Low-speed cables have a limit of 3 meters, while
full- and high-speed cables have a limit of 5 meters. (Since USB 1.0,
I don't think these numbers are in the spec, but this is what they
work out to according to the electrical specs.)  If a low-speed device
has a standard USB connector, a user might attach a 5-meter cable,
which might not work reliably. So compliant low-speed devices must
have either permanently attached cables or vendor-specific connectors.

As for cable sources, a search here will bring up many USB cable
manufacturers:

http://www.usb.org/app/search/products

Jan Axelson
http://www.Lvr.com

Re: Where can I find low speed USB cable?

[...]
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Close.  

The spec says a low-speed cable cannot have both a series A and series
B connector, but must instead be permanently attached to the low-speed
device (with a series A connector on the other end).  The reason for
this is as you state: to prevent users from inadvertantly plugging a
low-speed cable into a high-speed device.

So if you have a cable with both a series A and a series B connector,
it is either a high-speed cable, or does not conform to the spec.

Regards,

                               -=Dave
--
Change is inevitable, progress is not.

Re: Where can I find low speed USB cable?
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So I guess that, you can use a low speed device with a High speed cable,
they just don't want 'low speed' cables out there that could be plugged into
a high speed device.

So fitting a connector on the board and just a cable with plugs on both ends
to me would still seem the cheapest and best solution.

And *IF* you really wanted to have one end permanently attached, then put
the connector so that then connected cable sits inside the device using the
housing and the back of the plug as a strain relief.

Ralph



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