ao40tlmview can get the telemetry to be decoded from three different sources.

Local file

The filename of a file containing archived telemetry can be specified on the commandline using the -f filename option, or it can be given after typing f while ao40tlmview is running.

The file should contain the raw telemetry blocks of 512 bytes each (i.e., without sync vector, CRC bytes or padding). This is the same file format as used in the AO-40 telemetry archive at

http://www.amsat.org/amsat/ftp/telemetry/ao40/

Note: if the most-significant bit of the first byte is 1, the block is assumed to have been received with bit errors (according to the CRC); this is a convention that ao40tlmview shares with other AO40 telemetry programs.

TCP connection

Receiving telemetry over a TCP connection can be useful for two purposes: watching via the internet live telemetry being received elsewhere, or connecting the ao40tlmview program to another program that e.g. can demodulate the beacon's audio signal via the computer's soundcard. In order to use this, you need to tell ao40tlmview to what machine and to what portnumber on that machine it should connect. This can be done on the commandline, using the -t hostname:portnumber option, or in the .ao40tlmviewrc file; see below. The keystroke command t only switches to the server given on the commandline; if not specified otherwise (through the -t option or the .ao40tlmviewrc file) this defaults to garc9.gsfc.nasa.gov:1024, which is the server through which several amateurs often send their live telemetry feeds.

The data format expected by ao40tlmview for telemetry via TCP is the same as the one used by several other (MS-Windows) programs, such as P3T and ao40rcv, and used over the garc server. In this format, for every block an 8 byte sync vector (hex 2f,8f,6e,4d,28,86,75,60) is transmitted first, folllowed by the block's 512 data bytes and its 2 CRC bytes.

UDP packets

Receiving telemetry over UDP is quite similar to receiving over TCP. Again, it can be configured either on the command line, using the -u hostname:portnumber option, or in a .ao40tlmviewrc file (note that portnumber is now the portnumber to which the remote host is sending the packets, not its source port number). If no UDP source is specified, the u keystroke defaults to localhost:2222.

The data format ao40tlmview expects over UDP, is Phil Karn's Satellite Telemetry Protocol

http://people.qualcomm.com/karn/papers/telem.txt

Some soundcard telemetry demodulation software supports this.

When live reception, either over TCP or UDP, is activated, all received blocks are written to a file with a name Tyymmdd.RAW in the current directory, where yy , mm and dd are year, month and day. If a callsign has been defined in a .ao40tlmviewrc file (see below), this callsign will be included in the filename: Tyymmdd@callsign.RAW

After the computer's clock passes midnight UTC, the file is closed, and a new file (with the new date in its name) is opened. However, in order not to split up data belonging to one pass, this is by default postponed until no telemetry has been received for an hour. This timeout can be changed in the .ao40tlmviewrc file, see below.

The log file serves two purposes: it enables you to browse through the received telemetry blocks (although this could also have been achieved by storing the blocks in memory), and archival for later use and/or for submission to the telemetry archive, see http://www.amsat.org/amsat/ftp/telemetry/ao40/ ; ao40tlmview writes the files in the recommended format for the archive.

If you are demodulating the telemetry using one of the soundcard demodulator programs, you may want to choose TCP rather than UDP for the connection: with UDP a block is sent as one packet after it has been completely received, while with TCP each byte can be sent immediately after reception so you can see the block come in byte-by-byte.

Ao40tlmview does not (yet) support direct connection of a hardware modem to a serial port. The reason is simple: I don't have such a modem, so can't test it; if you have a modem and would be willing to test, please contact me.

ao40tlmview's display consists of several windows, each displaying a part of the received telemetry. The 'RAW' window shows every received block; the other windows decode the binary telemetry data transmitted in 'A'- and 'E'-type blocks, and don't change when other block types are received.

ao40tlmview has two layouts for the windows: one requiring a screen of at least 118x37 (columns x rows), the other requiring 80x60. The layout which fits best to your terminal size will automatically be chosen; if your screen is too small, the TAB key can be used to select which part is displayed.

In the interest of using the screen as efficiently as possible, the display is rather terse, using colours and abbreviations. The following colour conventions are used:

•

numerical data: labels in normal white; values in bright white; values of non-functional sensors in dark gray (or dark blue on terminals (like xterm) that don't support the 'dim' attribute).

•

on/off settings: ON reverse video; OFF dark gray (or dark blue on some terminals), or normal white if the text also serves as a label (e.g. in the matrix display).

•

red background in the 'RAW' window means the CRC failed.

•

colours in the matrix diagram don't mean anything special, they only serve to help identify what is connected to what.

Some possibly non-trivial abbreviations :

o

omni-directional antenna (with V, U, L1 and L2 receiver/transmitter).

bth

both antennas (L1 and L2 receiver). If it says just "L1" or "L2", the high-gain antenna is connected.

GB+

general beacon with the FSK bit activated.

N J I S

For LEILA: Notch, Jam, IHU control, Scan

SunS.

Sun Sensor

See also the 'Glossary' section of the telemetry specification.

Source selection:

f

open file

t

open TCP connection

u

start listening for UDP packets

Navigation:

left, up

go to previous block

right, down

go to next block

page-up

go back 16 blocks

page-down

go forward 16 blocks

home

go to first block

end

go to last (most recent) block

<

go to previous block of same class (i.e., 'A'-type, 'E'-type, or other)

>

go to next block of same class (i.e., 'A'-type, 'E'-type, or other)

q

quit

View:

a

Toggle decoding of 'A'-type blocks (which contain current telemetry).

e

Toggle decoding of 'E'-type blocks (which contain data from past events).

c

Toggle decoding blocks with incorrect CRC.

g

Display a graph of one or two telemetry channels as a function of time. The channel(s) is/are chosen by typing their (hexadecimal) channel numbers; after typing 'g', these numbers are displayed instead of the received data. If DISPLAY is set and gnuplot is available, gnuplot is used for showing the graph in a separate X11 window; otherwise, a crude ASCII-graph is shown.

G

If the current block is a Whole Orbit Data block, display a graph of its contents.

r

Toggle display of 'raw' data vs. data converted to engineering units.

R

Toggle display of (hexadecimal) channel numbers instead of received data.

x

Toggle hexadecimal display of entire block.

TAB

Change which part of display in viewable, if screen is too small to view all at once.

Upon startup, ao40tlmview searches the user's home directory and the current working directory for a file called .ao40tlmviewrc This file can be used to change some of the default settings, using the following format:

callsign ab1cde

specifies the callsign to be included in the telemetry capture file names (default: none).

logfiledelay 300

sets the timeout for switching to a new log file after midnight UTC to 300 seconds (default: 3600 seconds).

Note: even if you set this timeout to 0, you should not count on the previous file being closed exactly at midnight, since ao40tlmview only checks the time once a minute.

tcp hostname:port

sets the hostname and port for TCP connections, just like the -t commandline option does.

udp hostname:port

sets the hostname and port for UDP connections, just like the -u commandline option does.