"Jack Erbes" wrote in message
...
Doug Dotson wrote:

Where does A/D conversion come into the picture?


And the wrong answer buzzer goes off again! I guess I pulled that piece
of jargon out of a dark corner of my mind and used it incorrectly. As you
know, I'm an operator, not a technician. :)

I meant whatever goes on inside the IC that does the conversion. That IC
is what, a bridge or transceiver? I read different terms and sometimes
misuse them not understanding exactly what they mean.

It's usually a microprocessor with tranceivers for both the serial and USB
side. The conversion fromserial-USB is not trivial enough for a simple
tranceiver or bridge.

As an aside question, I have a small mouse type GPS receiver, an Altina
GGM-308. It has an in line PS2 (Mini-DIN 6) connector that lets the
receiver be adapted to a number of different power/PDA adapters.

The leads in the connector a

1 - TX (RS232)
2 - +5VDC
3 - TX (TTL)
4 - Ground
5 - RX(TTL)
6 - RX (RS232)

I've been using the serial (NMEA) output and that works fine.

I've also been wondering if the TX(TTL) and RX(TTL) leads are the outputs
for USB ports. Or if some device is needed to handle the transition
between the GPS and a USB port.

No, USB is a totally different animal from a serial port. The TTL level
outputs
allow the GPS to be directly interface to digital circuits such as a
microprocessor.
The easiest way to use USB is with a serial (RS232) to USB adapter.

I've been reluctant to simply connect 3 and 5 to a USB port data pins to
see what happens.

Jack

--
Jack Erbes in Ellsworth, Maine, USA - jackerbes at adelphia dot net
(also receiving email at jacker at midmaine.com)