[Xastir] Config file for TM-D710A config script?

[Curt, WE7U]

On Sun, 3 Jul 2011, Bill V WA7NWP wrote:

>> Okay!  So EVERYTHING "speaks" KISS on some level... including things like
>> PSK-31, Olivia and RTTY?
>
> There's more about KISS here than needed but here's the original
> definition document:
>
>  http://www.ka9q.net/papers/kiss.html
>
> While it could be used for other modes it's generally just a simple
> basic protocol to interface between the computer and a dumb TNC for
> (AX.25) packet.

It's really just the over-the-air bits put into a packet, with some extra bit stuffing added to escape some special characters that the KISS protocol uses.  A TNC in kiss mode pretty much only controls PTT, sends received bits up to the computer after adding the KISS framing, or sends bits out the radio after stripping off the KISS framing.  There are special KISS packets for sending timing parameters from the computer to the TNC.  I have one TNC that ignores those special packets and only does the data packets back and forth (PTT timing is controlled by a pot:  A TNC-X).

KISS protocol is evident when you hook a dumb terminal program to it and see packets coming across where the header is gibberish and the data portion of the packet is readable.  You often get screen-control characters coming across in that 8-bit binary data so your cursor does goofy things too.  The header portion of an AX.25 packet has ASCII characters which are shifted by a bit or two, then the low-bits are used by the protocol.  There are a few other bytes in the header such as control and protocol identifier bytes as well.  For this protocol you want to look at the AX.25 specification, version 2.0.  We don't currently use the newer published protocol, which I think is 2.2.

To confuse the matter even more, many of us have done TCP/IP over AX.25, both in AX.25 connected mode and in datagram mode.  So we're doing:

     TCP over IP over KISS over AX.25

If I had something like Zilog 8530 chips on a card inside the PC, I could skip the KISS mode entirely, but it's necessary in this case to get the packets down a serial port into the TNC.

Of course that last about TCP/IP has nothing to do with APRS.  I have done multiple protocols on the APRS frequency before with good effect:  APRS and Opentrac, both using AX.25 protocol, but using different PID bytes for each.  I was using Linux and AX.25 talking KISS to the TNC.  Xastir has OpenTrac receive code in it, but not transmit code.

-- 
Curt, WE7U.        http://www.eskimo.com/~archer
Additional pages:  http://wetnet.net/~we7u