1MINIMODEM(1) General Commands Manual MINIMODEM(1)
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6 minimodem - general-purpose software audio FSK modem
7
9 minimodem --tx [options] {baudmode}
10 minimodem --rx [options] {baudmode}
11
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 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 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
27 -t, --tx, --transmit, --write
28 transmit mode: generate audio tones
29 -r, --rx, --receive, --read
31 receive mode: decode audio tones
32
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 {any floating point value N}
41 : Bell202-style at N bps --ascii
42 1200 : Bell202 1200 bps --ascii
44 300 : Bell103 300 bps --ascii
46 rtty : RTTY 45.45 bps --baudot --stopbits 1.5
48 tdd : TTY/TDD 45.45 bps --baudot --stopbits 2.0
50 same : SAME 520.83 bps --startbits 0 --stopbits 0 --sync-byte 0xAB
52 NOAA Specific Area Message Encoding (SAME) protocol
53 callerid
55 : Bell202 1200 bps Caller-ID (MDMF or SDMF) protocol
56 uic-train
58 : UIC-751-3 600 bps train-to-ground message protocol
59 uic-ground
61 : UIC-751-3 600 bps ground-to-train message protocol
62
64 -a, --auto-carrier
65 Automatically detect mark and space frequences from carrier.
66 -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 -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 -8, --ascii
90 ASCII 8-N-1
91 -5, --baudot
93 Baudot 5-N-1.5
94 -f, --file filename.wav
96 encode or decode an audio file (extension sets audio format)
97 -b, --bandwidth {rx_bandwidth}
99 -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 -M, --mark {mark_freq}
107 -S, --space {space_freq}
109 --startbits {n}
111 Sets the number of start bits (default is 1 for most baudmodes).
112 --stopbits {n.n}
114 Sets the number of stop bits (default is 1.0 for most baud‐
115 modes).
116 --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 -q, --quiet
125 Do not report CARRIER / NOCARRIER or signal analysis metrics.
126 -R, --samplerate {rate}
128 Set the audio sample rate (default rate is 48000 Hz).
129 -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 --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 --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 --rx-one
150 Quit after the first carrier/no-carrier event (applies to --rx
151 mode only).
152 --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 --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 --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 --tx-carrier
174 When transmitting from a blocking source, keep a carrier going
175 while waiting for more data.
176 --benchmarks
178 Run and report internal performance tests (all other flags are
179 ignored).
180 -V, --version
182 print program version
183
185 minimodem --tx 100
186 Transmit 100 baud tones from one computer ...
187 minimodem --rx 100
189 and receive 100 baud tones on another nearby computer.
190 minimodem --rx -a rtty
192 Decode amateur radio RTTY signals (listen near 14.085 MHz).
193 minimodem --rx same
195 Decode NOAA SAME protocol emergency alert transmissions, e.g.
196 <http://en.wikipedia.org/wiki/Specific_Area_Message_Encoding>.
197 minimodem --tx 0.5
199 Experiment with very low baud rates (works in noisy conditions).
200 minimodem --tx 12000
202 Experiment with very high baud rates (works with audio files).
203
205 minimodem does not decode AX.25 framed packets.
206 minimodem does not support modem control ("AT") commands, nor does it
208 produce DTMF telephone dialing tones.
209
211 This page documents minimodem version 0.24. The latest version is
212 available at <http://www.whence.com/minimodem>.
213
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.
222 June 10, 2013 MINIMODEM(1)