usb problems

[Gene Heskett]

On Sunday 12 October 2014 09:29:14 Colin Law did opine
And Gene did reply:
> On 12 October 2014 14:18, Gene Heskett <gheskett at wdtv.com> wrote:
> >> RS232 specifies a min of +-3 volts up to +-15 if I remember
> >> correctly, so +-5 should be fine.
> > 
> > And is rated to take surges to at least 25 volts, usually more from
> > most chip vendors.
> > 
> > But is it enough to power the internal circuitry?  Or do these
> > converters have built in charge pumps running on the +4.5 or so they
> > can get from the USB port?  Its plugged into a powered hub, and its
> > blue power led is the usual brightness.
> 
> They get their power from the USB port.  A silly question I know, but
> you have got tx going to rx in each direction I presume.
> 
> Colin

Same cabling has been in use for 2 or 3 years, and we don't have mice. ;-)

FWIW, I got it to work again by changing the converter adapter to an older 
one.  And there seems to be no difference in the p-p output of the level 
translator chip when its wired back up for the full +- 12 volts.

And, the new chip isn't running any warmer that the one I pulled out, so I 
haven't glued a radiator to it yet. So, either this older adapter is a bit 
more tolerant of a slight baud rate error than the newer pair I have is, 
or both of the new ones are toast.  The actual baud rate as measured by 
the scope is in the 114 kilobaud range, can't be adjusted unless we can 
cut a machine cycle in halves or quarters.  The cpu clock in the other 
machine is only 1.78 mhz!

This whole Rube Golderg lashup can occasionally, after a lightning storm, 
die and needs a power down reset, something like a CMOS chips substrate 
phantom SCR turnon.  The extension cable now in use is a full 10 meters 
long, supposedly a no-no on USB, but when I found out it Just Worked(TM), 
I bought 2 more of them. Still, 2 years later, in the poly bags, haven't 
needed them.  OTOH the house service has been overhauled with the required 
by NEC grounding twice as part of the overhaul was a transfer switch with 
the backside being fed by a 20kw nat gas standby.  Much better grounded 
that it was prior to my installing a newer service in 2008 as I was 
building a garage over the old one that I never did find a ground system 
on.

Anyway, its working again, and I'm a happy camper.  That little two line 
bash post was helpful as it did prove the data path the other way worked,  
so a special thanks to that responder.

Cheers, Gene Heskett
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