How to safely test USB connector installation

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Okay, I admit it, I've screwed it up before and I don't want to do it again.
I have several Single Board Computers that have SBC headers on them and I
have to run a commercial cable from the headers to a standard USB chassis
connector.  The polarity of the USB header isn't obvious on some of these
boards and I have destroyed the USB interface on one of them by plugging a
device into the USB with the header on rotated 180 degrees.  I don't want to
do this again.

How can I test a USB setup in a (completely) non-destructive manner?  I'm
more than comfortable using DVMs and even oscilloscopes but I really don't
know what I can measure that will assure me that the connector is on the
board correctly.

    TIA
        Norm


Re: How to safely test USB connector installation
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again.
to

Well, if you download the USB spec from www.usb.org, you can see which
contacts carry the 5V. So you can measure with a DVM whether these contacts
carry 5V in the right polarity. You can then safely plug in a device to see
if the polarity of the datalines was ok or not.

Meindert



Re: How to safely test USB connector installation
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I
chassis
these
a
want
I'm
don't
contacts
see

    Sure -- but without experience with that bus, I wasn't sure that this
would be a "perfect" test.  If you're right -- and the next poster has a
really nice suggestion of making a test cable with LEDs (and resistors, of
course), it'll be trivial to check every board from here on out.

    Thanks
        Norm


Re: How to safely test USB connector installation
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Kensington sell a USB-powered LED-on-a-stick which would seem to do the job.
http://www.kensington.com/html/1176.html



Re: How to safely test USB connector installation

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job.

That won't do the job. You'll probably wreck it with reverse polarity and
because it has charge storage you'd have to wait an hour for the LED to go
out after you disconnected it.

Peter


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Re: How to safely test USB connector installation
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a
resistors,

Actually, my wife has one just like that.  Thanks for the warning.

    Norm


Re: How to safely test USB connector installation

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That's interesting. I didn't think that these were anything more than an LED
and a resistor. What else do they have in them?



Re: How to safely test USB connector installation
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LED

I reckon he's confused by the statement  'Uses less than 90 seconds of
battery charge per hour'

ie the power used by the LED in an hour is equivalent to running the laptop
for about 90 seconds. I looks to me like it's just an LED and a resistor in
some snazzy packaging. Anyone actually  taken one of these things to bits?

Richard



Re: How to safely test USB connector installation MY RESOLUTION
I found at
    http://cablesonline.com/usbdainusb.html

an inexpensive USB tester -- it's currently selling for $5! and it's already
saved me because as soon as I got it I plugged it into a known good
computer's port and then into the CPU board and it showed that one is wired
correctly and one isn't!  That's an incredible return o nmy investment since
it would have taken me at least 5-10 minutes to hack up a cable and connect
a meter.

    Norm


Re: How to safely test USB connector installation

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I'd make a test cable. Cut up a USB cable and add some resistors and LEDs
between vcc and ground. Have a GREEN led light up for a good connection and
RED for bad. Then plug it into your SBC and check for a green light before
you connect any USB devices.

You can work out which pins to use on here
http://www.starmount.co.uk/s_usbpin.htm

Peter


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Re: How to safely test USB connector installation
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You also could buy a cable tester. This will normally test RJ-45, RJ-11
(phone jack) and USB. Today they are relatively cheap.


Re: How to safely test USB connector installation
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I'm
don't
LEDs
and
before

I've seen RJ-45, RJ-11, and coax testers but never noticed a USB one.  I'll
have to check my preferred supplier's catalog again.

    Thanks much for the suggestion.

    Norm


Re: How to safely test USB connector installation
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Mine is called Skymaster Remote Cable Tester DCJ-0102 (made in Taiwan),
testing RJ-45, RJ-11, USB and BNC (coax).

Link to the new version of this tool:
<http://www.fonitech.com/catalog/product_info.php?cPath57%&products_id47%6

    Trygve


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