Afskmodem
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!!! DIESE SEITE IST NOCH IM AUFBAU !!!
Über afskmodem
afskmodem ist ein leistungsfähiger Zweiwege Multichannel und Multibaud Dekoder/Enkoder für AFSK/FSK AX.25 paketbasierte Datenübertragung (Packet Radio, APRS).
- Die Kommunikation mit einem Digi bzw. iGate erfolgt im AXUDP Format
- Audioquelle bzw. -ziel können jedes OSS Soundsystem (weitere Infos siehe unten), aber auch Dateien sein (auch Audiopipes).
- Für reine RX-Systeme kann afskmodem zusammen mit rtl_tcp und sdrtst auch mit gewöhnlichen USB RTL SDR-Sticks verwendet werden (z.B. RX only iGate)
- afskmodem unterstützt zeitgleich maximal acht Modems mit je maximal zwei channels (Stereo). Theroretisch wären pro Modem auch mehr channels möglich, ist aber einerseits kompliziert zu lösen und andererseits auch sehr praxisfern. Infos dazu gibt es bei Bedarf bei Chris OE5DXL direkt.
Zu OSS: Die Zusammenarbeit mit dem ALSA Soundsystem ist derzeit nicht möglich und auch nicht geplant. Eine Linuxdistribution mit eingebautem OSS ist TinyCore Linux in einer Version kleiner als v4.55. Auch Distributionen mit eingebautem alsaoss könnten funktionieren. Praxistests dazu gibt es aber nicht, hier kann noch viel experimentiert werden.
Kurzübersicht der Parameter
afskmodem -h
first for all modems
-a abort on sounddevice error else retry to open
-b <num> tx dacbuffers (10) (more to avoid underruns)
-B bad sound driver repair, sending continuous quietness to avoid receive
sample loss on start/stop of sound output. Use for stereo or fullduplex)
-c <num> maxchannels (1) (1=mono, 2=stereo)
-D <filename> (debug) write raw soundcard input data to file or pipe
-D <filename>.txt (debug) write demodulated bits as "01.." to file or pipe
-e <num> additional ptt hold time (if soundsystem has delay) unit=adcbuffers (1)
-f <num> adcrate (16000) (8000..96000)
-h help
-i <filename> kiss pipename (/dev/kiss/soundmodem)
-k <num> tx kiss bufs (60)
-l <num> adcbuffer length (256) more: lower system load but slower reaction
-m [<mixername>:]<channel>:<left>:<right> (0..255) ossmixer (/dev/mixer)
-o <filename> oss devicename (/dev/dsp)
-o <infilename,outfilename> /dev/stdin,outpipe (mknod outpipe p)
for play/rec with sox use -B as sox/alsa can only continuous sound
play -r 16000 -t raw -e signed-integer -c 1 -b 16 --buffer 1000 -q
rec -r 16000 -t raw -c 1 -b 16 -q - | afskmodem -B -f 16000 -o /dev/stdin,outpipe ...
make PTT with VOX as io-bits are not synchrone to sound with variable delay
-s <num> fragment size in 2^n (9)
repeat for each channel -C ... :
-C <num> (0..1) channel parameters follow (repeat for each channel)
-p <devname> <pttbit> pttport and bit to switch
* /dev/ttyXX for serial
* /dev/parport0 for parallel
* gpio for kernel gpio-interface
choose value for <pttbit>:
* tty: 0=RTS, 1=DTR
* parport: 0...7 / -0...-7 (inverted)
-u close ptt-tty file between switch actions, may not work on USB tty
-f <num> (0) (0=halfduplex, 1=master fullduplex, 2=all fullduplex,
3=simplex 'stereo never both tx same time')
-g <ms> GM900 audio quiet time after ptt on (0)
-r <num> max random wait time after dcd before start tx (ms) (800)
repeat for each modem -M ... :
-M <num> (0..7) modem parameters follow (repeat for each modem)
-a afsk off, fsk on (on)
-b <num> baud (1200) (1..32000)
-B <kbyte> send BERT, (negative bytes receive only)
-c <num> use stereo channel 0=left (or mono), 1=right
-d <num> dcdlevel, 0 no dcd (56) (0..100)
-e <num> demod equalizer (0) 100=6db/oct highpass (-999..999)
-f <num> afsk mid frequency, tx and rx (hz) (1700)
-g g3ruh scrambler on (off)
-H <num> afsk tx highpass (0) (0..100)
-i ignore modem parameters from kiss (off)
-k <num> received data send to this kiss port (0) (0..7)
-m <num> monitor (2) (0=off, 1=header, 2=all, 3=passall)
-n <num> nyquist filter baseband -6db point in % of baudrate (65) (0..100)
-P same as -U but use AXUDP v2, send dcd and txbuffer empty messages
-p <num> receive clock pll aquisition speed (16) (num/256 of bit time)
-q <num> quiet adc level to save cpu or avoid reciption of channel crosstalk (0)
-s <num> afsk shift tx (for rx bandfilter width) (1000) (hz)
-t <num> txdelay (300) (ms)
-T <seconds> timeout for tx buffered frame (60) (s)
-U <[x.x.x.x]:destport:listenport> use axudp instead of kiss /listenport check ip
-L same as -U but use AXUDP v2 (no dcd and txbuffer empty messages)
-v <num> tx loudness (100)
-w <num> txdelay pattern before 1 flag (126) (0..255)
-x <num> txtail (20) (ms), ptt hold for fullduplex
-z <num> fsk rx baseband dc regeneration clamp speed (996) (0=off, 1=fast, 999=slow)
example: ./afskmodem -f 22050 -c 2 -C 0 -p /dev/ttyS0 0 -M 0 -c 0 -b 1200 -M 1 -c 1 -b 9600 -a -g -U 127.0.0.1:6001:1093
Ausführliche Beschreibung der Parameter
Parameter für alle Modems
| Parameter | Beschreibung |
|---|---|
| a | abort on sounddevice error else retry to open |
| b <num> | tx dacbuffers (10) (more to avoid underruns) |
| B | bad sound driver repair, sending continuous quietness to avoid receive sample loss on start/stop of sound output. Use for stereo or fullduplex) |
| c <num> | maxchannels (1) (1=mono, 2=stereo) |
| D <filename> | (debug) write raw soundcard input data to file or pipe |
| D <filename>.txt | (debug) write demodulated bits as "01.." to file or pipe |
| e <num> | additional ptt hold time (if soundsystem has delay) unit=adcbuffers (1) |
| f <num> | adcrate (16000) (8000..96000) |
| h | Hilfe |
| i <filename> | kiss pipename (/dev/kiss/soundmodem) |
| k <num> | tx kiss bufs (60) |
| l <num> | adcbuffer length (256) more: lower system load but slower reaction |
| m [<mixername>:]<channel>:<left>:<right> | (0..255) ossmixer (/dev/mixer) |
| o <filename> | oss devicename (/dev/dsp) |
| o <infilename,outfilename> | afskmodem -B -f 16000 -o /dev/stdin,outpipe ... make PTT with VOX as io-bits are not synchrone to sound with variable delay |
| s <num> | fragment size in 2^n (9) |
Wiederholend für jeden channel
| Parameter | Beschreibung |
|---|---|
| C <num> | (0..1) channel parameters follow (repeat for each channel) |
| p <devname> <pttbit> | pttport and bit to switch * /dev/ttyXX for serial * /dev/parport0 for parallel * gpio for kernel gpio-interface choose value for <pttbit>: * tty: 0=RTS, 1=DTR * parport: 0...7 / -0...-7 (inverted) |
| u | close ptt-tty file between switch actions, may not work on USB tty |
| f <num> | (0) (0=halfduplex, 1=master fullduplex, 2=all fullduplex, 3=simplex 'stereo never both tx same time') |
| g <ms> | GM900 audio quiet time after ptt on (0) |
| r <num> | max random wait time after dcd before start tx (ms) (800) |
Wiederholend für jedes Modem
| Parameter | Beschreibung |
|---|---|
| M <num> | (0..7) modem parameters follow (repeat for each modem) |
| a | afsk off, fsk on (on) |
| b <num> | baud (1200) (1..32000) |
| B <kbyte> | send BERT, (negative bytes receive only) |
| c <num> | use stereo channel 0=left (or mono), 1=right |
| d <num> | dcdlevel, 0 no dcd (56) (0..100) |
| e <num> | demod equalizer (0) 100=6db/oct highpass (-999..999) |
| f <num> | afsk mid frequency, tx and rx (hz) (1700) |
| g | g3ruh scrambler on (off) |
| H <num> | afsk tx highpass (0) (0..100) |
| i | ignore modem parameters from kiss (off) |
| k <num> | received data send to this kiss port (0) (0..7) |
| m <num> | monitor (2) (0=off, 1=header, 2=all, 3=passall) |
| n <num> | nyquist filter baseband -6db point in % of baudrate (65) (0..100) |
| P | same as -U but use AXUDP v2, send dcd and txbuffer empty messages |
| p <num> | receive clock pll aquisition speed (16) (num/256 of bit time) |
| q <num> | quiet adc level to save cpu or avoid reciption of channel crosstalk (0) |
| s <num> | afsk shift tx (for rx bandfilter width) (1000) (hz) |
| t <num> | txdelay (300) (ms) |
| T <seconds> | timeout for tx buffered frame (60) (s) |
| U <[x.x.x.x]:destport:listenport> | use axudp instead of kiss /listenport check ip |
| L | same as -U but use AXUDP v2 (no dcd and txbuffer empty messages) |
| v <num> | tx loudness (100) |
| w <num> | txdelay pattern before 1 flag (126) (0..255) |
| x <num> | txtail (20) (ms), ptt hold for fullduplex |
| z <num> | fsk rx baseband dc regeneration clamp speed (996) (0=off, 1=fast, 999=slow) |
Konfigurationsbeispiele
SDR mit Einkanalempfang
afskmodem -f 16000 -o /home/pi/dxlAPRS/aprs/aprspipe -c 1 -M 0 -c 0 -L 127.0.0.1:9001:0
SDR mit Zweikanalempfang
afskmodem -f 16000 -o /home/pi/dxlAPRS/aprs/aprspipe -c 2 -M 0 -c 0 -L 127.0.0.1:9001:0 -M 1 -c 1 -L 127.0.0.1:9002:0