EQUiSat Decoder

A GNU radio Out-Of-Tree Module and custom blocks to decode EQUiSat's 4FSK transceiver

Dependencies

• GNU Radio (this repo is a GNU Radio "module")
• Swig (usually available in package managers; required for GNU Radio to generate Python bindings from C++)
• See requirements.txt for additional Python dependencies (run pip install -r requirements.txt )

Build and Installation

Run:

pip install -r requirements.txt # if you haven't
git submodule init # for BrownSpaceEngineering/packetparse
git submodule update
mkdir build
cd build
cmake ..
make
sudo make install
sudo ldconfig

Running

There are GNU Radio flowgraphs in apps/ that you can "compile" and run as follows:

grcc <flowgraph>.grc
python <flowgraph>.py # run the generated python file

You can also open the flowgraph in GNU Radio Companion and click "generate" instead of using grcc

These flowgraphs are:

apps/equisat.grc

This flowgraph listens for packets from a UDP audio stream from the GQRX SDR software or other frontends (see below). Usually all you need to do is click the "UDP" button in the bottom right of the GQRX interface, but if you have reconfigured GQRX you may need to specify a host and port to the Python script; see python equisat.py --help for how to.

If you don't have or don't want to use GQRX as a frontend, check out gr-frontends for alternative scripts that also stream over UDP. This repo provides frontends for SDRs, file sources, and other sources.

If any complete packets are successfully received, they will be printed to the screen along with the data fields found in the packet. To automatically publish good packets to Brown Space Engineering's database, see below.

apps/equisat_fm_input.grc

This flowgraph does essentially the same decoding as equisat.grc, but requires that you specify a FM-demodulated wav file to use as input using the --wavfile= parameter. It also does not publish to our API yet. You may also need to specify --sample-rate if your file was not recorded at 48kHz.

Publishing to EQUiSat's telemetry database

You can publish good received packets to Brown Space Engineering's database server by specifying the following as command line arguments to the flowgraphs above:

• A station name/callsign
• Your latitude/longitude (optional)
• If you're replaying a recording, the UTC time it started at
• An API key. To generate one, run the generate-api-key.sh script in the root of the repository.

You can run python equisat.py --help for specifics. We'd really appreciate it if you send us your data!