APRS(9) XR32 REFERENCE MANUAL 4/2/2013
NAME
APRS -- Automatic Packet Reporting System.
DESCRIPTION
APRS is (currently) an acronym for "Automatic Packet Reporting
System", although the name tends to change from time to time!
(it was originally called "Automatic *Position* Reporting
System, and there has been talk of re-branding it to Automatic
PRESENCE Reporting System).
It is a protocol that uses AX25 UI frames and digipeaters to
report a wide variety of parameters such as position, weather,
speed, bearing, status, objects, frequencies and so on.
XR32 includes the following sub-systems that support or make
use of APRS:
- APRS Generic Digipeating
- APRS Igate
- APRS Server
- APRS Messaging Shell
- APRS Weather reports
- APRS DX recording
- APRS Queries
- Positions, distances & directions in MH lists
Generic digipeating is a complex type of digipeating which
responds to special digipeater addresses, and modifies a
packet's digipeater addresses in transit. It also prevents
duplicates and looping.
The Igate is a client daemon that allows APRS data to flow to
and from between the Internet APRS system and RF ports,
messaging shell etc.
The APRS server allows APRS applications such as UI-view to
use XR32 to access all the APRS data handled by XR32.
The APRS messaging shell allows users to send and receive APRS
messages and bulletins.
Weather reports are received via RF and/or Igate, and are made
available for users to read using the WX command.
The DX feature stores a list of the furthest stations heard
via RF.
APRS Queries allow RF users to query which nodes are on
channel, what DX they've heard, what messages are waiting etc.
MHeard lists are able to display the positions, bearings and
distances of stations that broadcast APRS data.
Specifying XR32's Position
~~~~~~~~~~~~~~~~~~~~~~~~~~
In order for most of these systems to work, XR32 needs to know
its position on the globe. There are currently 2 ways to
achieve this...
The easiest method is to use the "LOCATOR=" directive in
XROUTER.CFG, which enables you to specify an approximate
location at the centre of a 1Km "Maidenhead" locator square,
e.g. "LOCATOR=IO82VJ".
The second method, which allows more precise (or less precise
if you prefer) positioning, is to include an APRS-style
position in IDTEXT, starting within the first 40 characters.
The format is "!ddmm.mmN/dddmm.mmE#" where dd represents
degrees of latitude/longitude and mm.mm represents minutes to
two decimal places. "N" and "E" may be replaced by "S" and "W"
as appropriate. For example:
IDTEXT
!5224.00N/00215.00W# Kidderminster Router (KDRMIN)
***
You are urged to use at least one of these methods to define
XR32's position. It really does make Packet more interesting!
APRS Generic Digipeating
~~~~~~~~~~~~~~~~~~~~~~~~
XR32 supports APRS generic digipeating for RELAY, WIDE,
TRACE, TRACEn-N and WIDEn-N aliases.
Generic digipeating is configured on a port by port basis,
using the flags marked "*" in "DIGIFLAG" as follows:
1 Digipeat UI frames (note 1)
2 Digipeat non-UI frames (note 1)
*4 Enable RELAY generic digipeating.
*8 Enable TRACE generic digipeating.
*16 Enable WIDE (Well sited stations only!)
*32 Allow APRS 3rd party digi via L4.
*64 Allow digipeating to Internet (IGate).
*128 Allow digipeating from Internet (IGate).
*256 Enable UITRACE digipeating
*512 Enable UIFLOOD digipeating
Add the appropriate numbers together to enable the
desired combination of services.
Note 1: Irrespective of the generic digipeater settings, you
may choose to allow regular digipeating (i.e. using XR32's
normal callsign or alias) on APRS ports, allow regular UI-only
digipeating, or disable regular digipeating altogether, by
manipulating bits 0 and 1 of DIGIFLAG.
SSID Substitution Digipeating
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
UITRACE and UIFLOOD represent two special addresses that are
suffixed with pseudo-SSID's, e.g. "TRACE4-4" and "WIDE2-2".
These addresses can digipeat several times. The first digit
specifies the maximum number of hops, and the second is the
hop counter, which is decremented each time the frame is
digipeated.
These two addresses behave slightly differently however. When
a frame is digipeated on the alias specified by UITRACE, each
digipeater inserts its own callsign in the digipeater list,
and decrements the "SSID". Frames digipeated on the UIFLOOD
address have their SSIDs decremented, but the digi doesn't
insert its own callsign.
For the sake of consistency with UI-View, UITRACE defaults to
"TRACE", giving TRACEn-n digipeating, and UIFLOOD defaults to
WIDE, giving WIDEn-n digipeating.
New-N Paradigm
~~~~~~~~~~~~~~
According to the APRS "New-N Paradigm", RELAY, TRACE and WIDE
are deprecated, UITRACE should be set to "WIDE", and UIFLOOD
should be set to a "state" code (e.g. "GBR" for the UK).
One of the main reasons for the New-N Paradigm was the fact
that some of the older digipeaters would digipeat the same
packets over and over. This does not happen with XR32 however.
Not everyone agrees with the "New-N Paradigm, so the choice of
which features to enable is left you you.
Mixing Modes
~~~~~~~~~~~~
In quiet areas, you may wish to mix APRS and normal
connected-mode operations on the same port, and that is the
default if you enable any of the above flags in DIGIFLAG.
However, in most areas, APRS tends to be on a separate
frequency reserved for "unconnected nets", and you may wish to
prevent people from connecting to the node or downlinking from
it on your APRS-only ports.
The CFLAGS keyword can be used in the PORT section of the
XROUTER.CFG file to control uplinking and downlinking as
follows:
0 Prevent uplinking and downlinking.
1 allow uplinking only.
2 allow downlinking only.
3 allow both up and downlinking.
ID Beacons
~~~~~~~~~~
Whilst all sysops are urged to include an APRS position in
their normal IDTEXT, a dedicated APRS port may require a more
detailed and cryptic ID beacon, therefore you may define a
different IDTEXT for each port if necessary.
A "regular" port would include a position followed by some
human-readable text, whereas the APRS-only ports would include
additional data such as power / height / gain / direction,
wind speed, bowel movements etc., in encoded format.
The IDTEXT may be sent via digipeaters by including the IDPATH
keyword in the relevant port configuration section of
XROUTER.CFG.
Dupe Suppression
~~~~~~~~~~~~~~~~
XR32 checks for its own callsign or alias in previously-used
digipeaters to prevent digi looping. It will not digipeat
frames it originated, and will not digipeat the same frame
within 9 seconds.
DX Facility
~~~~~~~~~~~
The "DX [port]" command shows the best received APRS DX. It
only works if XR32's position has been defined as described
earlier.
The DXFLAGS keyword in the .CFG file controls whether or not
the DX list contains callsigns heard via digipeaters.
The DX list may be queried by RF stations, by means of APRS
queries.
APRS / UI-View queries
~~~~~~~~~~~~~~~~~~~~~~
XR32 responds to the following general queries:
?APRS? All stations query.
~\xFD~ UI-View general query.
?IGATE? Igate query.
The response to the first two is the ID beacon for the port,
which should contain the APRS position and station type. The
response to the ?IGATE? query shows the message and local
user counts.
The following "directed" queries (directed at portcall) are
supported:
?APRSD Directly heard stations list.
Responds with a list of stations heard directly
on the receiving port (i.e. not via digipeaters
or via 3rd party networks)
?APRSM Un-delivered messages query.
If there are any un-delivered or expired
messages addressed to the sender of the query,
they are re-activated and transmitted on the port
which received the query.
?APRSP Station Position.
If the sysop has defined XR32's position, it is
sent in response to this query.
?APRSS Station status.
The response consists of the software type and
version plus a list of the enabled generic
digipeater calls.
?PING?
?APRST Trace Route.
Both of these return the route by which the
query was received.
~\xFE~n UI-View "ping".
The response to this query is a UI-View ack for
the ping id.
~\FC~n UI-View "DX" query.
Responds with a UI-View ack, followed by details
of the best DX heard directly by XR32 (digipeated
packets are NOT included!)
See www.aprs.org for more info about APRS.
SEE ALSO
AMSG(1) -- APRS Messaging Mode.
APRS-SRV(9) -- APRS Server.
DX(1) -- Display Distant APRS stations.
IGATE(9) -- APRS Igate.
MHEARD(1) -- Display Recently Heard Stations.
MHEARD(9) -- About the MHeard Facility.
WX(1) -- Display APRS Weather Information.
XROUTER.CFG -- Main Configuration File.
APRS(9) END OF DOCUMENT
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