Forums

How to safely test USB connector installation

Started by Norm Dresner December 1, 2004
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" <ndrez@att.net> wrote in message
news:eQfrd.77850$7i4.11192@bgtnsc05-news.ops.worldnet.att.net...
> 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.
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" <ndrez@att.net> wrote in message
news:eQfrd.77850$7i4.11192@bgtnsc05-news.ops.worldnet.att.net...
> 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 >
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 --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.779 / Virus Database: 526 - Release Date: 19/10/04
"Meindert Sprang" <mhsprang@NOcustomSPAMware.nl> wrote in message
news:10qr4v16v7tjb2b@corp.supernews.com...
> "Norm Dresner" <ndrez@att.net> wrote in message > news:eQfrd.77850$7i4.11192@bgtnsc05-news.ops.worldnet.att.net... > > 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. > > 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.
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 wrote:
> "Norm Dresner" <ndrez@att.net> wrote in message > news:eQfrd.77850$7i4.11192@bgtnsc05-news.ops.worldnet.att.net... > >>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. > > 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
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" <trselmer@start.no> wrote in message
news:41AE220B.6020704@start.no...
> moocowmoo wrote: > > "Norm Dresner" <ndrez@att.net> wrote in message > > news:eQfrd.77850$7i4.11192@bgtnsc05-news.ops.worldnet.att.net... > > > >>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. > > > > 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 > > You also could buy a cable tester. This will normally test RJ-45, RJ-11 > (phone jack) and USB. Today they are relatively cheap.
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 wrote:
> "Trygve Selmer" <trselmer@start.no> wrote in message > >>You also could buy a cable tester. This will normally test RJ-45, RJ-11 >>(phone jack) and USB. Today they are relatively cheap. > > 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.
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?cPath=57&products_id=476> Trygve
"Norm Dresner" <ndrez@att.net> wrote in ...
> "Meindert Sprang" <mhsprang@NOcustomSPAMware.nl> wrote ... > > "Norm Dresner" <ndrez@att.net> wrote ... > > > 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. > > > > 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. > > 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.
Kensington sell a USB-powered LED-on-a-stick which would seem to do the job. http://www.kensington.com/html/1176.html
> > > > 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. > > Kensington sell a USB-powered LED-on-a-stick which would seem to do the
job.
> http://www.kensington.com/html/1176.html > >
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 --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.779 / Virus Database: 526 - Release Date: 19/10/04
"moocowmoo" <meltyb@hotmail.com> wrote in message
news:comnj9$7nj$1$830fa795@news.demon.co.uk...
> > > > > > > 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. > > > > Kensington sell a USB-powered LED-on-a-stick which would seem to do the > job. > > http://www.kensington.com/html/1176.html > > > > > > 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
Actually, my wife has one just like that. Thanks for the warning. Norm