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

[James Ewen]

On Sun, Jul 3, 2011 at 3:06 PM, Jarett DeAngelis
<jdeangelis at alumni.nd.edu> wrote:

> All right then, still more confusion!
> I thought TNCs operated in three modes:
>
> KISS, which is "barebones" and allows application software to manage how the
> TNC interprets bits,
>
> Serial, which makes certain assumptions about how data is handled (kind of
> like a modem for phones),
>
> AX.25, which creates a protocol specific network adapter on the OS level
> that many applications can access (useful for Xastir and IP applications)
>
> Am I wrong here?

You're a little mixed up...

The link to the packet radio primer takes you off on a bit of a
tangent. It does have a bit of information relevant to your query, but
it takes you on a rambling tour of BBSes and Nodes, etc.

All TNCs and packet radio are serial devices. They send data one bit
at a time over the air. You also talk to them from the computer in a
serial manner as well, whether using the serial port, or a USB device.

AX.25 is a protocol definition, it defines the "language" that the
TNCs speak to each other over the air in a serial stream..

KISS is a manner of framing the packets that uses AX.25 to send data
over the air in a serial manner.

You can't do KISS without using AX.25... you can't do AX.25 without
sending data via a serial data stream over the air.


You're more likely thinking of things at a higher level...

You can run a TNC in KISS mode. That leaves all the dirty work of
building the packet frames to be sent, and decoding the packet frames
when the are received up to the controlling program. The program has
to build the complete frame, including the header and other
information. It takes more work to get the packet out, but the program
has ultimate control over what goes out over the air.

The next level up is sometimes called "text mode". Here all that the
program has to do, is present the information to be sent out over the
air to the TNC. The TNC looks after building the frame. When the
packet is received, the TNC pulls the user data out of the incoming
data stream, and presents that to the user.

There's also another level up where the radio has APRS smarts built
into it, where the data is deciphered and displayed on screen for the
user rather than having "raw" data presented. The Kenwood and Yaesu
rigs are examples of this.

Wikipedia gives a fairly concise rundown of the workings of AX.25.

http://en.wikipedia.org/wiki/AX.25

It might help to get a basic understanding of the OSI communications
model as well...

http://en.wikipedia.org/wiki/OSI_model

Some of what you are talking about (serial communications) is at layer
1 the physical layer, some (KISS) at layer 2 data link layer whereas
the APRS interfaces of the Kenwood and Yaesu radios is up at layer 7
the application layer. (This doesn't exactly fit the full OSI model,
but it gives you a basic concept of how each layer builds upon those
below it).

Think of it this way... APRS modes in the Kenwood and Yaesu radios is
like riding in a limo with a chauffeur. Drop down to plain old text
mode, where the packet contents get delivered to you, and you're now
the one driving the car. Back down to KISS mode, and we've just handed
you a big box of parts where you get to build the car before you get
to go for a drive. If you want to drag AX.25 into this analogy, we'll
have to give you some chunks of steel and CAD drawings of what the
parts need to look like for you to build the car.

Generally the deepest we go is into KISS mode where the packet frames
have to be built up and decoded within the program accessing the TNC.
encoding and decoding the bits into audio, keying the radio, carrier
detection and the like is all looked after by the TNC hardware.

-- 
James
VE6SRV