usb problems

[Colin Law]

On 12 October 2014 11:47, Gene Heskett <gheskett at wdtv.com> wrote:
> 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.

As Nils said, since it appears as /dev/ttyUSB1, you can just write to
it as if it were a serial port, using echo for example.

Colin