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README: update usage section
This commit is contained in:
Roman Zeyde
77
README.md
77
README.md
@@ -9,7 +9,7 @@ This program can be used to transmit a specified file between 2 computers, using
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a simple audio cable (for better SNR and higher speeds) or a simple headset,
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allowing true air-gapped communication (via a speaker and a microphone).
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The sender modulates an input binary data file into an 32kHz audio file,
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The sender modulates an input binary data file into an 32kHz audio file,
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which is played to the sound card, using `aplay` Linux utility.
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The receiver side uses `arecord` Linux utility to record the transmitted audio
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@@ -56,28 +56,87 @@ following scripts:
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~/receiver $ amodem recv --calibrate
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```
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Increase the sender computer's output audio level, until the
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received **amplitude** and **peak** values are not higher than 0.5,
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while the **coherence** is 1.0 (to avoid saturation).
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Change the sender computer's output audio level, until
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all frequencies are received well:
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```
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1000 Hz: good signal
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2000 Hz: good signal
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3000 Hz: good signal
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4000 Hz: good signal
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5000 Hz: good signal
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6000 Hz: good signal
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7000 Hz: good signal
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8000 Hz: good signal
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```
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If the signal is "too weak", increase the sender's output audio level.
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If the signal is "too strong", decrease the sender's output audio level.
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If the signal is "too noisy", please re-run the receiver for at least 10 seconds:
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```
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~/receiver $ amodem recv --wave >recording.raw
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```
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and please send me `recording.raw` file for debugging.
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# Testing
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- Prepare the sender (generate random binary data file to be sent):
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```
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~/sender $ dd if=/dev/urandom of=data.tx bs=125kB count=1 status=none
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~/sender $ dd if=/dev/urandom of=data.tx bs=16kB count=1 status=none
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~/sender $ sha256sum data.tx
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008df57d4f3ed6e7a25d25afd57d04fc73140e8df604685bd34fcab58f5ddc01 data.tx
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```
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- Start the receiver:
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- Start the receiver, which will wait for the sender to start:
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```
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~/receiver $ amodem recv >data.rx
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~/receiver $ amodem -vv recv >data.rx
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```
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- Start the sender:
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- Start the sender, which will modulate the data and start the transmission:
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```
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~/sender $ amodem send <data.tx
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~/sender $ amodem -vv send <data.tx
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```
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- A similar log should be emitted by the sender:
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```
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2014-10-23 09:46:36,116 DEBUG MODEM settings: {'F0': 1000.0, 'Nfreq': 8, 'Fs': 32000.0, 'Npoints': 64, 'Tsym': 0.001} amodem:126
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2014-10-23 09:46:36,116 DEBUG Running: ['aplay', '-', '-q', '-f', 'S16_LE', '-c', '1', '-r', '32000'] wave.py:20
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2014-10-23 09:46:36,665 INFO Sending 2.150 seconds of training audio send.py:69
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2014-10-23 09:46:36,665 INFO Starting modulation: <48.000 kbps, 64-QAM, 8 carriers> send.py:74
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2014-10-23 09:46:37,735 DEBUG Sent 6.0 kB send.py:56
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2014-10-23 09:46:38,794 DEBUG Sent 12.0 kB send.py:56
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2014-10-23 09:46:39,440 INFO Sent 16.384 kB @ 2.754 seconds send.py:79
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```
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- A similar log should be emitted by the receiver:
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```
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2014-10-23 09:46:36,116 DEBUG MODEM settings: {'F0': 1000.0, 'Nfreq': 8, 'Fs': 32000.0, 'Npoints': 64, 'Tsym': 0.001} amodem:126
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2014-10-23 09:46:36,238 DEBUG Running: ['arecord', '-', '-q', '-f', 'S16_LE', '-c', '1', '-r', '32000'] wave.py:20
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2014-10-23 09:46:36,408 DEBUG Skipping 0.128 seconds recv.py:275
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2014-10-23 09:46:36,409 INFO Waiting for carrier tone: 1.0 kHz recv.py:282
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2014-10-23 09:46:37,657 INFO Carrier detected at ~886.0 ms @ 1.0 kHz: coherence=99.996%, amplitude=0.475 recv.py:40
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2014-10-23 09:46:37,657 DEBUG Buffered 1000 ms of audio recv.py:64
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2014-10-23 09:46:37,660 DEBUG Carrier starts at 9.531 ms recv.py:73
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2014-10-23 09:46:38,119 DEBUG Prefix OK recv.py:108
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2014-10-23 09:46:38,153 DEBUG Current phase on carrier: -0.497 recv.py:121
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2014-10-23 09:46:38,153 DEBUG Frequency error: 0.02 ppm recv.py:123
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2014-10-23 09:46:38,682 DEBUG 1.0 kHz: SNR = 34.20 dB recv.py:165
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2014-10-23 09:46:38,715 DEBUG 2.0 kHz: SNR = 35.05 dB recv.py:165
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2014-10-23 09:46:38,766 DEBUG 3.0 kHz: SNR = 35.52 dB recv.py:165
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2014-10-23 09:46:38,803 DEBUG 4.0 kHz: SNR = 35.65 dB recv.py:165
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2014-10-23 09:46:38,837 DEBUG 5.0 kHz: SNR = 35.03 dB recv.py:165
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2014-10-23 09:46:38,869 DEBUG 6.0 kHz: SNR = 35.05 dB recv.py:165
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2014-10-23 09:46:38,907 DEBUG 7.0 kHz: SNR = 34.80 dB recv.py:165
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2014-10-23 09:46:38,943 DEBUG 8.0 kHz: SNR = 33.74 dB recv.py:165
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2014-10-23 09:46:38,977 INFO Starting demodulation: <48.000 kbps, 64-QAM, 8 carriers> recv.py:197
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2014-10-23 09:46:39,619 DEBUG Got 6.0 kB, realtime: 64.18%, drift: +0.02 ppm recv.py:215
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2014-10-23 09:46:40,538 DEBUG Got 12.0 kB, realtime: 78.03%, drift: +0.02 ppm recv.py:215
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2014-10-23 09:46:41,306 DEBUG EOF frame detected framing.py:60
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2014-10-23 09:46:41,306 DEBUG Demodulated 16.520 kB @ 2.329 seconds (84.6% realtime) recv.py:244
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2014-10-23 09:46:41,306 INFO Received 16.384 kB @ 2.329 seconds = 7.034 kB/s recv.py:247
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```
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- After the receiver has finished, verify that the file's hash is the same:
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