Old Notes

Some notes that used to be in the main README.

WARNING: The below information is partly outdated. Use the above installation guide.

Main Programs

• rx/rx_ssdv.py - Reads in received packets (256 byte SSDV frames) via stdin, and decodes them to JPEGs. Also informs other processes (via UDP broadcast) of new ssdv and telemetry data.
• rx/rx_gui.py - Displays last received image, as commanded by rx_ssdv.py via UDP.
• tx/init_rfm22b.py - Set RFM22B (attached via SPI to the RPi) into Direct-Asynchronous mode.
• tx/init_rfm98w.py - Set RFM98W (attached via SPI to the RPi) into Direct-Asynchronous mode. Note that this requires pySX127x from https://github.com/darksidelemm/pySX127x
• tx_picam_gps.py - Captures pictures using the PiCam, overlays GPS data and transmits them.

Testing Scripts

• Run python compress_test_images.py from within ./test_images/ to produce the set of test ssdv-compressed files.

TX Testing

• tx_test_images.py transmits a stream of test images out of the RPi UART. Check the top of the file for settings.
• This script can also be used to produce a one-char-per-bit output, which is what would be seen by the modulator.

RX Testing

• rx_tester.py produces a stream of packets on stdout, as would be received from the fsk_demod modem.
• Run python rx_tester.py | python rx_ssdv.py to feed these test packets into the command-line ssdv rx script.
• add --partialupdate N to the above command to have rx_gui.py update every N received packets.

Sending/Receiving Images

TX Side

Refer to the instructions here: https://github.com/projecthorus/wenet/wiki/Wenet-TX-Payload-Instructions

RX Side

Refer to the instructions here: https://github.com/projecthorus/wenet/wiki/Wenet-RX-Instructions-(Linux-using-Docker)

RX Tips.

• It is highly recommended to use a preamplifier in front of your RTLSDR to lower the overall noise figure of the system. With a NooElec RTLSDR (R820T2 Tuner) and a HabAmp, we were able to achieve a Minimum-Detectable-Signal (MDS - which we defined as the point where we get no packet errors) of around -112 dBm.
• If needed, the transmit bitrate can be slowed down by editing the defaults in tx_picam.py. You will then have to determine the appropriate parameters for fsk_demod and the preceding filtering/resampling chain to be able to receive this bitrate.