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[aprssig] Really CHEAP Puck-type USB GPS Receiver

Greg Dolkas ko6th.greg at gmail.com
Sat Jan 21 06:35:44 UTC 2012


...and what we casually call RS-232 these days is really RS-423 if I recall
correctly.  Different signal levels; RS-232 is something like +/- 25 volts,
vs something a lot less than that now, but otherwise generally compatible.

But the point is that we should be able to get at the right information a
lot cleaner than going through all the transformations with USB stuck in
the middle.  But hooking things end-to-end (with USB in there) might be
easier.

Greg  KO6TH

p.s.  for extra credit, where did the signal designations AB, CD, etc. come
from?  (Hint: CD didn't mean Carrier Detect, even though that was what that
pin did...)


On Fri, Jan 20, 2012 at 10:18 PM, Steve Noskowicz <noskosteve at yahoo.com>wrote:

>
> --- Boyde asked:
> I wonder if the puck could be opened up and a serial cable (terminated in
> a DB-9 or some such) be soldered on before the USB conversion?
> Boyd Prestwood K5YKG
>
>
> --- Sander Pool wrote:
> ... Boyd asked if a serial -cable- could be soldered in front of
> the USB circuitry. The answer is still 'no', sorry. You need to add a
> MAX232 or something similar to do the level conversion.
> ...     Sander W1SOP
>
>  Which sounds/is completely correct.  The GPS engine has to talk TTL to
> communicate with the USB chip, which, signal-wise, could be converted to
> RS-232 with a Max232 chip or equivalent.  It could be something lower in
> voltage level too, e.g. 3 v cmos.
>  Opening, digging, adding hacker type stuff, YMMV, yadda yadda pip pip
> cherio and all that stuff.
>
>  That said...  some things called simply "cable" these days also have
> conversion circuitry in them making the distinction between a simple cable
> (wires and connectors only) and a level converter with cables attached
> blurred.
>
> Now, for the important stuff. (;-)
>
>  The D-Sub connector referred to is a DE-9, not a DB-9.  I called it that
> for a long time as many do; and usually still do in mixed company.  The "B"
> is the shell size and the 25 pin shell is the "B".  The 9 pin shell is an
> "E" size.  When it was 25 pins, we just got used to using the B.
>  So there!  Put that in your smoke and pipe it.
>
> Happy 2012, Steve, K9DCI
> (;-)
>
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