[aprssig] Sharing GPS

[Jason KG4WSV]

On Tue, Dec 26, 2017 at 1:03 PM, Michael Barnes <barnmichael at gmail.com> wrote:

> I'm thinking there must be some way to get a serial output from the RPi to
> feed the other radios.

You'd think so, but I haven't found a way short of writing my own software.

You'd be better off with an RS232 GPS, and sharing that output among
the Pi, Kenwood, ICOM, and Uniden receivers.

For example, this guy

https://www.argentdata.com/catalog/product_info.php?products_id=174

could probably tie directly to the Pi via the Pi expansion header
(power to the GPS, plus TTL level UART signals for the Pi), and use
the DB9 to send the GPS data to the radios.  Check the documentation
yourself, don't confuse my 34 seconds of web surfing for actual
research.

Technically RS232 is point to point (one TX, one RX), but the reality
is you can probably get away with tying multiple RX lines to a single
TX, especially over the short distances in your vehicle and the low
speeds used by NMEA.

>  I do not have the other radios in hand yet, so I am
> not sure of the exact interfacing required, only that is is serial data.

almost everything uses the NMEA standard, which specifies 4800/8/N/1
as well as the data protocol. That part shouldn't be too difficult -
what works for one will probably work for all.

-Jason
kg4wsv