clark@tomcat.gsfc.nasa.gov (Tom Clark -- W3IWI) (11/28/90)
Archive-name: pacsat/26-Nov-90
Original-posting-by: clark@tomcat.gsfc.nasa.gov (Tom Clark -- W3IWI)
Original-subject: PACSAT software on tomcat
Archive-site: tomcat.gsfc.nasa.gov [128.183.10.100]
Archive-directory: /public/microsat
Reposted-by: emv@ox.com (Edward Vielmetti)
The following note from Jeff Ward (G0/K8KA) and Harold Price (NK6K) gives a
brief description of the initial release of PACSAT ground-station software.
The files are posted on tomcat.gsfc.nasa.gov in the /public/microsat
directory ..... Tom
-----------------------------------
AO-16 Status 11/22/90
The new version of the BBS is up and running on AO-16 as of
11/23/90 5:00 UTC. It is available for use.
Jeff Ward's broadcast protocol receiver software is now available on
compuserve DL 5 and on tomcat /microsat. In addition to receiving
broadcast files, logging kiss frames to disk, and displaying data in
realtime, it also allows users to request that a file be placed on the
broadcast queue for five minutes. Also included are programs to
manipulate the pacsat headers placed on each file. The file names are
pbrel.zip and phsrel.zip.
The file upload program (PG) will be available in the next few days.
PG is currently the only way to get a list of file titles and file
numbers. The numbers are then either used by PG to download a file or
by PB to request a broadcast. A facility to broadcast the directory will
be added in the near future. In the meantime, we will attempt to keep
the broadcast queue full of interesting files.
We will be adding new features to the spacecraft software in the coming
weeks. We'll attempt to limit outages to UTC Wednesdays (the old
experimental days).
Misc notes:
The file numbers start with 0x100 on this incarnation. This is to
avoid duplicates, using the same number for two different files, the
broadcast protocol requires that file numbers not be reused.
AO-16 will allow four concurrent connected users. Since file uploads
and downloads work automatically from pre-prepared files, each user
will use a large amount of channel time. There is then an advantage
in keeping the number of concurrent users small, this makes each
connection run more efficiently, which will cause it to end quicker, and
allow the next user to connect. This is different from a system that
permits users to compose messages while they are connected; since most
of them will be thinking at any one time, you can have a larger number
of them without overloading the channel.
We hope that the "pacsat" scheme will maximize throughput and ultimately
serve a larger number of users.
A new status packet has been added, BBSTAT. This shows the callsigns
of the connected users, and also whether or not a slot exists for a new
user to log into. It also shows what uplink channels the current
connected users are on, allowing new stations to pick an idle channel.
The format is:
OPEN ABCD: call1 call2 call3 call4
or
FULL ABCD: call1 call2 call3 call4
If a slot is available, OPEN is sent, otherwise FULL is sent.
If none of the current users are being heard on a particular channel,
its letter appears, if a channel is being used, its letter does not
appear. There is no requirement that each session be on a different
channel, but there would be less collisions if they were. For
example, if WD0E and NK6K were logged in and using channel A, and
N4HY was using channel D, the status message would be:
OPEN BC : WD0E NK6K N4HY
Channel letters and frequencies are:
AO-16
a 145.900
b 145.920
c 145.940
d 145.960
LO-19
a 145.840
b 145.860
c 145.880
d 145.900