In article <or0JUBA6VGe4EwuF@...>, Roger Barker
<roger@...> writes
[snip]
Does anyone know where I can get the PacComm cable in the UK?
Wot, no answer? ;-) I think that must mean it isn't available in the UK!
Another question then - If I implement support for sharing a COM port
between the TNC and the GPS, how many subscribers to this list have got
any hardware that can take advantage of it? If anyone has got anything,
then I'd be really interested to know what it is, and what *exactly* is
required for switching between its two inputs. (You can't simply
parallel two devices on one COM port, there has to be some external
hardware involved that can select one or the other, usually by using the
RTS and DTR lines.)
I've now had a good look at sharing the port, and I've got it working,
but the big problem is that I have no knowledge of what hardware is
available, other than what I have used for testing.
I built the two transistor switch as detailed in the DOS APRS GPS.TXT
file. However, it didn't work with some TNCs in KISS mode (not a problem
for DOS APRS, because it doesn't support KISS), so I had to make a
modification. It uses two transistors, three diodes and four resistors,
so it's easy enough to build, the only problem is building it in a
sufficiently neat and robust format for mobile use.
I believe some TNCs have a port for attaching a GPS, but I haven't got
one, so any info as to what TNCs have this facility, and technical
details from the manufacturers notes as to how you switch between the
two inputs would be very useful.
--
Roger Barker, G4IDE roger@...
Boston
Lincolnshire, UK
