usb problems

Gene Heskett gheskett at wdtv.com
Sun Oct 12 10:47:30 UTC 2014


On Sunday 12 October 2014 00:29:21 NoOp did opine
And Gene did reply:
> On 10/11/2014 05:28 PM, Gene Heskett wrote:
> > Hello all;
> > 
> > I am in need of a tool that will effectively do a ping against a
> > specified USB port, a port I know there is something on the other
> > end of the cable and hub as I just had a printer do a test page over
> > the same cabling. Basically I want to send a $55 down the cable once
> > a second to a specified port, in thgius case /dev/ttyUSB1, for
> > oscilloscope troubleshooting, at least as long as trouble doesn't
> > shoot back... ;-)
> > 
> > Do we have such a beast?
> > 
> > I have a copy of Randy Dunlap's usbtree, a perl module, but with
> > kernel 3.16.0, its returning null + linefeed only. I have not used
> > this utility in probably 2 years. So with a newer kernel, it may not
> > work.  But it is not complaining either.  "Puzzling" seems to fit.
> > 
> > 
> > Thanks for any clues, urls etc.
> > 
> > Cheers, Gene Heskett
> 
> You could possibly modify/tailor '/usr/bin/usb-devices' to suit your
> needs.
> <http://manpages.ubuntu.com/manpages/oneiric/man1/usb-devices.1.html>

These are good at listing things, with usb-devices show all the stuff 
plugged in, while lsusb apparently only shows that which is active.

What I have is a software bitbanger port on a legacy computer that is 
outputting data I can see on a scope, but which appears to be getting lost 
in the serial<->USB converter.  Some of these things are quite fussy about 
the baud rate, and will ignore a stream of input data that is not within 
say 2% of the correct baud rate, in this case supposedly 115kb.

I have a new digital 100mhz dual trace scope, so I guess I'll have to 
measure a baud/bit and see what its speed actually is.  If its off, there 
is likely no way to fix it as its an extremely tightly coded loop to drive 
that port at that speed on the old Color computer 3. But, its been working 
nicely for a couple years.

Occasionally the green led on the converter will flash once or twice, 
working right, its flickering brightly continuously as long as data is 
flowing.  It also does the same for incoming data but with a red led.  The 
program that monitors what comes in on /dev/USB1 says no data is arriving, 
but its a server, so it only responds to a data request, so isn't sending.  
Thats why I need a ping-like function, so I can exercise both directions 
of the circuit.

If we had the ability to "usbping /dev/USB1" then I would, or should be 
able to see if its traceable with the scope.

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>
US V Castleman, SCOTUS, Mar 2014 is grounds for Impeaching SCOTUS




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