Groups > sci.electronics.design > #446719

Re: USB cabling constraints

From	rickman <gnuarm@gmail.com>
Newsgroups	sci.electronics.design
Subject	Re: USB cabling constraints
Date	2017-02-07 20:37 -0500
Organization	A noiseless patient Spider
Message-ID	<o7dskj$qoo$1@dont-email.me> (permalink)
References	<o7cpr0$nno$1@dont-email.me> <o7csgl$4bg$1@dont-email.me>

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On 2/7/2017 11:28 AM, amdx wrote:
> On 2/7/2017 9:43 AM, Don Y wrote:
>> Are there any rules/guidelines for manufacturing/designing USB2
>> cable assemblies?
>>
>> Compared to the constraints on network cables and SCSI cables,
>> are they somewhere in-between?  Microphone cables?
>>
>> Or, more like ZIP cord for speakers?  :>
>
>  I don't know*, but I just bought a cheap usb to apple iPod connector
> cable. I hadn't charged the iPod for years, (it was one of my kids).
>  I plugged it in and the battery charged, before I got to down load
> and data I dropped it and the plastic shell came off of the connector.
>  I notice the white wire had been heated to the point the wire melted
> out of the insulation, of the four strands! one was broken. OK it wasn't
> touching anything so, whatever. But then I noticed two of the wires were
> shorted together at the pins. Looked up the connector and the Data+ and
> Data- were solder together. So, I cleaned it all up and put it back
> together. Now it doesn't even recognize the usb has been plugged into
> the computer.
>
> * Well I have some clue to your question, this cheap cable has no
> shield, the wire is smaller that a #40 and there are 4 strands.
> I was not able to see any twist.
>   Tested with ohmmeter and it all checks correct. But no long will
> charge the battery.

I don't know the exact rules in the specs, but there are different specs 
for different speeds.  USB 1.2 Mbps I don't think uses a shield.  Check 
if your mouse has a shielded cable, I bet not... assuming it has a cable 
at all.


>   A google search show, quality cables have a shield, the data pair are
> and power pair are twisted.
>
>> https://www.google.com/search?q=usb+cable+diagrams&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjEpN2Usv7RAhXJeSYKHakKDgsQ_AUICCgB&biw=1440&bih=687#imgrc=_

I expect 12 Mbps should have a shield and 480 Mbps and 4 Gbps absolutely 
need a shield as well as impedance control.

-- 

Rick C

Thread

USB cabling constraints Don Y <blockedofcourse@foo.invalid> - 2017-02-07 08:43 -0700
  Re: USB cabling constraints amdx <nojunk@knology.net> - 2017-02-07 10:28 -0600
    Re: USB cabling constraints jrwalliker@gmail.com - 2017-02-07 08:54 -0800
    Re: USB cabling constraints rickman <gnuarm@gmail.com> - 2017-02-07 20:37 -0500
    Re: USB cabling constraints Don Y <blockedofcourse@foo.invalid> - 2017-02-07 20:23 -0700
    Re: USB cabling constraints Robert Baer <robertbaer@localnet.com> - 2017-02-08 21:29 -0800
      Re: USB cabling constraints Kamen Lilov <kamenl@gmail.com> - 2017-02-09 14:01 -0800
  Re: USB cabling constraints Jeff Liebermann <jeffl@cruzio.com> - 2017-02-07 10:39 -0800
  Re: USB cabling constraints "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-02-07 19:06 -0600
    Re: USB cabling constraints Don Y <blockedofcourse@foo.invalid> - 2017-02-07 20:35 -0700
      Re: USB cabling constraints "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-02-08 17:49 -0600
        Re: USB cabling constraints Don Y <blockedofcourse@foo.invalid> - 2017-02-08 20:33 -0700
          Re: USB cabling constraints "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-02-09 16:43 -0600
            Re: USB cabling constraints Don Y <blockedofcourse@foo.invalid> - 2017-02-09 16:18 -0700

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