SignalEasel is a C++ library for audio modulation and demodulation through a variety of analog and digital modes via PulseAudio and .wav files. It also provides encoding and decoding for higher level protocols.

Detailed Documentation

Repository

• APRS
  • Full encoding and decoding of APRS packets through continuous and discrete modes
  • Location (Compressed)
  • Telemetry Data Reports w/Parameter Metadata Messages
  • Messages with ACK/REJ
  • User Defined Packets
• AX.25
  • Encoding and Decoding of UI Frames
  • NRZI, CRC-16, Bit Stuffing
• AFSK
  • AFSK1200 (Bell 202)
  • ASCII mode for sending text
• BPSK & QPSK
  • Varicode and Convolutional Encoding (ARRL PSK31 Spec)
  • Fldigi mode at 125, 250, 500, 1000 baud
  • Also supports raw binary PSK without encoding
• Morse Code for additional station identification
• SSTV (Robot36, Optional Call Sign & data overlay)
  • Modulation only

There are a few optional features that require additional dependencies. These features can be toggled in the root CMakeLists.txt

option(USE_PULSEAUDIO ... ON)
option(SSTV_ENABLED ... OFF)
option(UNIT_TESTS ... OFF)

PulseAudio is required for real-time modulation and demodulation. If enabled, in the root CMakeLists.txt, SignalEasel will use PulseAudio for audio I/O. Without PulseAudio, you can still use the library to generate and read .wav files.

sudo apt-get install libpulse-dev

SSTV requires that you have magick++ installed with the modules related to fonts and the image formats you want to use. This is optional. If you want to use the other modes, then you do not need any 3rd party libraries. This library was developed on a Linux system but it may work on others.

Installation instructions: https://imagemagick.org/Magick++/Install.html

This library is designed to be used as a part of another CMake project. To use it, you simply add the subdirectory to your project and link against it.

add_subdirectory(lib/SignalEasel)

target_link_libraries(your_target SignalEasel)

Not recommended, but it's as simple as building the static library and including the include directory in your project.

# Clone the repository with submodules (WavGen and SSTV-Image-Tools)
git clone --recurse-submodules  https://github.com/joshua-jerred/SignalEasel

# Create and enter the build directory
cd SignalEasel && mkdir build && cd build

# Configure
cmake ..

# Build
make SignalEasel # Builds a static library at `build/libSignalEasel.a`

sudo apt-get update
sudo apt-get install build-essential
sudo apt-get install libjpeg62-dev libpng-dev libfreetype6-dev

git clone https://github.com/ImageMagick/ImageMagick.git ImageMagick-7.1.0
cd ImageMagick-7.1.0
./configure --with-modules
make -j8
sudo make install
sudo ldconfig # May need to do more for linking

• https://user.engineering.uiowa.edu/~eedesign/algorithm.pdf
• https://archive.org/details/dcc-2014-amateur-bell-202-modem-w-6-kwf-and-bridget-benson
• https://github.com/PhirePhly/aprs_notes