1MINIMODEM(1)                General Commands Manual               MINIMODEM(1)
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NAME

6       minimodem - general-purpose software audio FSK modem
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SYNOPSIS

9       minimodem --tx [options] {baudmode}
10       minimodem --rx [options] {baudmode}
11

DESCRIPTION

13       Minimodem  is a command-line program which decodes (or generates) audio
14       modem tones at any specified baud rate, using  various  framing  proto‐
15       cols.   It acts a general-purpose software FSK modem, and includes sup‐
16       port for various standard FSK protocols such as Bell103, Bell202, RTTY,
17       TTY/TDD, NOAA SAME, and Caller-ID.
18
19       Minimodem  can  play and capture audio modem tones in real-time via the
20       system audio device, or in batched mode via audio files.
21
22       Minimodem can be used to transfer data between nearby  computers  using
23       an  audio  cable (or just via sound waves), or between remote computers
24       using radio, telephone, or another audio communications medium.
25

TX/RX MODE

27       -t, --tx, --transmit, --write
28              transmit mode: generate audio tones
29
30       -r, --rx, --receive, --read
31              receive mode: decode audio tones
32

{baudmode}

34       The required {baudmode} parameter may be any  floating-point  value  to
35       specify  a baud rate, or any of the special keywords listed below.  The
36       {baudmode} also implies certain other parameter defaults  depending  on
37       the  rate, including standard (or at least reasonable) default mark and
38       space tone frequencies.
39
40       {any floating point value N}
41              : Bell202-style at N bps --ascii
42
43       1200   : Bell202 1200 bps --ascii
44
45       300    : Bell103 300 bps --ascii
46
47       rtty   : RTTY 45.45 bps --baudot --stopbits 1.5
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49       tdd    : TTY/TDD 45.45 bps --baudot --stopbits 2.0
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51       same   : SAME 520.83 bps --startbits 0 --stopbits 0 --sync-byte 0xAB
52                   NOAA Specific Area Message Encoding (SAME) protocol
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54       callerid
55              : Bell202 1200 bps Caller-ID (MDMF or SDMF) protocol
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57       uic-train
58              : UIC-751-3 600 bps train-to-ground message protocol
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60       uic-ground
61              : UIC-751-3 600 bps ground-to-train message protocol
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OPTIONS

64       -a, --auto-carrier
65              Automatically detect mark and space frequences from carrier.
66
67       -i, --inverted
68              Invert the mark and space frequencies (applies whether the  fre‐
69              quencies  are  defaults, discovered by --auto-carrier, or speci‐
70              fied manually).
71
72       -c, --confidence min-confidence-threshold
73              Set receive confidence minimum  threshold  (default  1.5).   The
74              "confidence"  value is a metric based primarily on the SNR (sig‐
75              nal-to-noise ratio) of the received signal.  This value acts  as
76              an  FSK decoder "squelch" control.  Increase to accept only very
77              clean signals (up to INFINITY, but a value around  5.0  is  more
78              practical).   Decrease  to accept partial decoding of noisy sig‐
79              nals (down to a minimum value of 1.0).  (This option applies  to
80              --rx  mode  only).   -l, --limit max-confidence-search-limit Set
81              receive confidence maximum  search  limit  (default  2.3).   The
82              "confidence"  value is as described above.  This value acts as a
83              performance vs.  analysis  quality  control.   Increase  (up  to
84              INFINITY)  for  a  more  pedantic analysis and higher CPU usage.
85              Decrease (down to the min-confidence-threshold) for  a  sloppier
86              analysis,  with  lower  CPU usage.  (This option applies to --rx
87              mode only).
88
89       -8, --ascii
90              ASCII  8-N-1
91
92       -5, --baudot
93              Baudot 5-N-1.5
94
95       -f, --file filename.wav
96              encode or decode an audio file (extension sets audio format)
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98       -b, --bandwidth {rx_bandwidth}
99
100       -v, --volume {tx_amplitude or 'E'}
101              Sets the generated signal amplitude (default is 1.0).  As a spe‐
102              cial  case  useful for testing, the value 'E' sets the amplitude
103              to the very small value FLT_EPSILON.  (This  option  applies  to
104              --tx mode only).
105
106       -M, --mark {mark_freq}
107
108       -S, --space {space_freq}
109
110       --startbits {n}
111              Sets the number of start bits (default is 1 for most baudmodes).
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113       --stopbits {n.n}
114              Sets  the  number  of  stop  bits (default is 1.0 for most baud‐
115              modes).
116
117       --sync-byte {0xXX}
118              If this option is used, initial carrier acquisition will be sup‐
119              pressed  until  after one or more consecutive data frame(s) con‐
120              taining this value are received.  This can be used  to  synchro‐
121              nize  the  stream  for  protocols which include a fixed preamble
122              byte.  (This option applies to --rx mode only).
123
124       -q, --quiet
125              Do not report CARRIER / NOCARRIER or signal analysis metrics.
126
127       -R, --samplerate {rate}
128              Set the audio sample rate (default rate is 48000 Hz).
129
130       -A, --alsa[={plughw:X,Y | X,Y | X }]
131              Use ALSA as the audio  output  system  instead  of  the  default
132              PulseAudio (depending on build configuration options).  The ALSA
133              device alias "default" is used, if  a  specific  device  is  not
134              specified.   For  example, the following options all select ALSA
135              device #1, sub-device #0:
136               --alsa=plughw:1,0  --alsa=1,0  -A1
137
138       --lut={tx_sin_table_len}
139              Minimodem uses a precomputed sine wave lookup table of 1024 ele‐
140              ments,  or  the size specified here.  Use --lut=0 to disable the
141              use of the sine wave lookup table.  (This option applies to --tx
142              mode only).
143
144       --float-samples
145              Generate  32-bit floating-point format audio samples, instead of
146              the default 16-bit signed integer format (applies to  --tx  mode
147              only; --rx mode always uses 32-bit floating-point).
148
149       --rx-one
150              Quit  after  the first carrier/no-carrier event (applies to --rx
151              mode only).
152
153       --binary-output
154              Print received data bits as raw binary output  using  characters
155              '0'  and  '1'.   The  bits  are  printed  in  the order they are
156              received.  Framing bits (start and stop bits) are  omitted  from
157              the output.  (This option applies to --rx mode only).
158
159       --binary-raw {nbits}
160              Print  all received bits (data bits and any framing bits) as raw
161              binary output using characters '0' and '1'.   Framing  bits  are
162              not  interpreted,  but simply passed through to the output.  The
163              bits are printed in  the  order  they  are  received,  in  lines
164              {nbits} wide.  So in order to display a standard 8-N-1 bitstream
165              (8 databits + 1 start bit + 1 stop bit), use "--binary-raw 10"
166               or a multiple of 10.  (This option applies to --rx mode only).
167
168       --print-filter
169              Filter the received text output, replacing  any  "non-printable"
170              bytes  with  a '.' character.  (This option applies to --rx mode
171              only).
172
173       --tx-carrier
174              When transmitting from a blocking source, keep a  carrier  going
175              while waiting for more data.
176
177       --benchmarks
178              Run  and  report internal performance tests (all other flags are
179              ignored).
180
181       -V, --version
182              print program version
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EXAMPLES

185       minimodem --tx 100
186              Transmit 100 baud tones from one computer ...
187
188       minimodem --rx 100
189              and receive 100 baud tones on another nearby computer.
190
191       minimodem --rx -a rtty
192              Decode amateur radio RTTY signals (listen near 14.085 MHz).
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194       minimodem --rx same
195              Decode NOAA SAME protocol emergency alert transmissions, e.g.
196              <http://en.wikipedia.org/wiki/Specific_Area_Message_Encoding>.
197
198       minimodem --tx 0.5
199              Experiment with very low baud rates (works in noisy conditions).
200
201       minimodem --tx 12000
202              Experiment with very high baud rates (works with audio files).
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NOTES

205       minimodem does not decode AX.25 framed packets.
206
207       minimodem does not support modem control ("AT") commands, nor  does  it
208       produce DTMF telephone dialing tones.
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VERSION

211       This  page  documents  minimodem  version  0.24.  The latest version is
212       available at <http://www.whence.com/minimodem>.
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AUTHOR

215       minimodem was written by Kamal Mostafa <kamal@whence.com>.
216
218       Copyright © 2011-2016 by  Kamal  Mostafa  <kamal@whence.com>.   License
219       GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
220       This  is  free  software:  you  are free to change and redistribute it.
221       There is NO WARRANTY, to the extent permitted by law.
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225                                 June 10, 2013                    MINIMODEM(1)
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