How to safely test USB connector installation

  • Thread starter Thread starter Norm Dresner
  • Start date Start date
N

Norm Dresner

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
 
Norm Dresner said:
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.
Click to expand...

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
 
Norm Dresner said:
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
Click to expand...

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
 
Meindert Sprang said:
want

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.
Click to expand...

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
 
moocowmoo said:
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
Click to expand...

You also could buy a cable tester. This will normally test RJ-45, RJ-11
(phone jack) and USB. Today they are relatively cheap.
 
Trygve Selmer said:
You also could buy a cable tester. This will normally test RJ-45, RJ-11
(phone jack) and USB. Today they are relatively cheap.
Click to expand...

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
 
Norm Dresner said:
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.
Click to expand...

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