A set of M17 tools based on original m17-cxx-demod toolset by Rob Riggs, WX9O.
A screenshot of m17-mod-gui running on Windows:
This program reads a 48k samples per second 16-bit, little-endian, single channel, M17 4FSK baseband stream from STDIN and writes a demodulated/decoded 8k SPS 16-bit, single channel audio stream to STDOUT.
Some diagnostic information can be written to STDERR while the demodulator is running.
This program reads in an 8k samples per second, signed 16-bit little-endian, single channel raw audio stream from STDIN and writes out an M17 4FSK baseband stream at 48k SPS, 16-bit, 1 channel to STDOUT.
This program connects to the running M17Gateway instance via selected port.
It translates M17-over-IP traffic (reflector traffic) to M17 baseband. External system commands can be used
for PTT signal control, see -T and -O options' description below.
This program connects to the running M17Gateway instance via selected port. It translates M17 baseband to the M17-over-IP traffic (reflector traffic).
This code requires the codec2-devel, boost-devel, gtest-devel [and libgl-dev, libasound2-dev, and xorg-dev for the gui app] packages be installed.
It also requires a modern C++17 compiler (GCC 8 minimum).
sudo apt-get install libgl-dev xorg-dev libasound2-dev
cd m17-tools
cd thirdparty/rtaudio
mkdir build
cd build
cmake ..
make
cd ../../../
mkdir build
cd build
cmake ..
make
make test
sudo make install
cd m17-tools
mkdir build
cd build
cmake .. -DBUILD_GUI_APPS=OFF
make
make test
sudo make install
sudo port install pkgconfig boost gtest portaudio codec2
Then follow the build steps above from "cd m17-tools".
- Microsoft Visual Studio 2019
- Miniconda (or Anaconda) x64 for Windows
conda config --add channels conda-forge
conda create -n M17 vs2019_win-64 cmake ninja pkg-config boost-cpp gtest gmock gtest libcodec2
conda activate M17
And then from the top level of the m17-tools repo, execute win_build.bat
This program was designed to be used with RTL-SDR, specifically rtl-fm.
rtl_fm -E offset -f 439.5M -s 48k | m17-demod -l | play -b 16 -r 8000 -c1 -t s16 -
You should run this in a terminal window that is at least 132 characters wide. It will output diagnostic information on a single line in the window.
sox 8k.wav -t raw - | ./m17-mod -S AB1CD -D AB2CD | ./m17-demod -l -d | play -q -b 16 -r 8000 -c1 -t s16 -
The input audio stream must be single channel, 16-bit little-endian, 8ksps. The output of the modulator is 48ksps, 16-bit little-endian, single channel raw audio.
If you have a 16 bit stereo 48000 Hz wav file, it can be converted to the input audio format with a command like the following:
sox /tmp/recorded.wav -r 8000 -b 16 -c 1 /tmp/8k.wav
To output a bitstream file:
sox 8k.wav -t raw - | ./m17-mod -S AB1CD -x > m17.bin
This bitstream file can be fed into m17-gnuradio to transmit M17 using a PlutoSDR, HackRF, or any SDR with an appropriate GNURadio sink. See the specification document for more details on file formats.
-h for general help
-S for the source callsign (alphanumeric string),
-D for the destination callsign (alphanumeric string),
-C for the Channel Access Number (0..15, default - 10),
-x for binary output (M17 baseband as a packed bitstream),
-r for raw audio output (single channel, signed 16-bit little endian, +7168 for the `+1` symbol),
-s for symbols output,
-d to dump additional debug info,
-K for AES key setting (hex format without the leading `0x`) - automatically checks keylength,
-T for PTT on command,
-O for PTT off command,
-l to enable LICH data dump,
-d to dump additional debug info,
-x for binary output,
-r for raw audio output,
-s for symbols output (signed 8-bit, 4.8k per second),
-K for AES key, automatic mute if encrypted transmission and no key provided.
The demodulator produces diagnostic output which looks like:
SRC: BROADCAST, DEST: AB3CD, TYPE: 0002, NONCE: 0000000000000000000000000000, CRC: bb9b
dcd: 1, evm: 13.27%, deviation: 0.9857, freq offset: 0.03534, locked: true, clock: 1, sample: 0, 0, 0, cost: 9
The first line shows the received link information. The second line contains the following diagnostics.
- DCD -- data carrier detect -- uses a DFT to detect baseband energy. Very good at detecting whether data may be there.
- EVM -- error vector magnitude -- measure the Std Dev of the offset from ideal for each symbol.
- Deviation -- normalized to 1.0 to mean 2400Hz deviation for the input from the following command:
rtl_fm -F 9 -f 439.5M -s 18k | sox -t s16 -r 18k -c1 - -t raw - gain 9 rate -v -s 48k-- the rates and gain are the important part. - Frequency Offset -- the estimated frequency offset from 0 based on the DC level of each symbol. The magnutude has not been measure but should be around 1.0 == 2kHz using the same normalized input as for deviation. Anything > 0.1 or less than -0.1 requires review/calibration of the TX and RX frequencies.
- Locked -- sync word detected.
- Clock -- estimated difference between TX and RX clock. Will not work if > 500ppm. Normalized to 1.0 -- meaning the clocks are equal.
- Sample -- estimated sample point based on 2 clock recovery methods. Should agree to within 1 always. There are 10 samples per symbol. Should never jump by more than 1 per frame. The third number is the "winner" based on certain heuristics.
- Cost -- the normalized Viterbi cost estimate for decoding the frame. < 5 great, < 15 good, < 30 OK, < 50 bad, > 80 you're hosed.
-A for M17Gateway address (optional)
-P for M17Gateway port (default: 17011)
-d to dump additional debug info,
-b for binary output (M17 baseband as a packed bitstream),
-T for PTT on command,
-O for PTT off command
-A for M17Gateway address (optional),
-P for M17Gateway port (default: 17011),
-d to dump additional debug info,
-l to enable LICH data dump
This code is based on previous work done by: Rob Riggs WX9O, Jay Francis KA1PQK, David Cherkus N1AI, and Paulo Duarte PU4THZ.