Hello Max,
Welcome to Xastir and Linux and I'm confident that you'll love both of them!
I have also been reading a little about AX.25 and at some point I think I would
like to have Xastir and APRX both running using AX.25. It's my understanding
that AX.25 makes the connection to the APRS-IS and the two applications would
use that connection, correct? Or is AX.25 only for the TNC to be shared and
each application still makes its own connection to the
APRS-IS? Do packets also get passed between the two applications ?
AX.25 is the low level communications protocol for packet radio which is
in turn used used by APRS. To elaborate, classic TNCs support AX.25
internally where they take your plain user data and format them into
AX.25 packets and then it out to the radio. I call this is "command
mode" operation . These same TNCs and specifically your TNC-Pi,
supports KISS mode which is a very plain serial protocol. This is where
your *computer* does all the AX.25 formatting, sends the resulting bits
over the serial port in KISS format, and the TNC dumbly spews out the
tones to the radio. Xastir supports APRS functionality either via
command mode or KISS but since you want to use a TNCPi (a small TNC-X
unit), you need to use KISS mode.
On the application side, APRS-IS is a very powerful system and typically
uses a TCP connection to inject objects into the Internet:
http://www.aprs-is.net/Connecting.aspx . Each connection from an APRS-IS
client application into the APRS-IS system is UNIQUE so if you have APRX
and Xastir connected to the APRS-IS system at the same time, those
connections are completely independent of each other. On the RF side of
things, if you configure your Linux machine to use the AX.25 protocol
stack, both APRX and Xastir can share that common infrastructure.
APRX can do several things including to inject APRS Objects into the
Internet relm as well can also inject Objects, digipeat, etc on the RF
side but doesn't display any of that data on a map. Xastir can also do
these same things but it can also support GPSes and can show interactive
maps of heard APRS posits. Arguably, Xastir can do everything APRX can
do and a lot more but it requires a lot more system resources.
What about when one application sends a packet to
the TNC, does it also come back in to the other application? I'm trying to
get the big picture here as to how all this works
together.
With the use of the Linux's AX.25 stack, both Xastir and the APRX
applications can see eachother's packets but each application needs to
have unique SSIDs.
Do you have a need to have APRX communicate directly with Xastir?
Ps. It's outside the scope of this list but I encourage you to NOT
compile things for your Raspberry Pi on it's SD card. You'll quickly
wear it out if you do this for long. Feel free to contact me offline if
you'd like a few hints on how to setup a build environment that won't
wear out your SD card.
--David
KI6ZHD
_______________________________________________
Xastir mailing list
[email protected]
http://lists.xastir.org/cgi-bin/mailman/listinfo/xastir
