PlutoSDR (or ADALM-PLUTO) is an inexpensive SDR (software-defined radio) platform by Analog Devices. It uses a Xilinx Zynq Z-7010 FPGA, which integrates an 32bit ARMv7 core together with the FPGA functionality.

This 32bit ARMv7 CPU runs Linux and is normally (when used as an SDR via USB) just passing libiio messages to the host computer.

The USB port on the PlutoSDR can also be used as a host/OTG port instead. By connecting a USB-to-Ethernet converter and a USB flash drive (or other form of storage), the PlutoSDR can be a standalone Linux machine, just like a Raspberry Pi (or similar single board computer).

This can be used to run applications directly on the PlutoSDR, such as fr24feeder, the application used by FlightRadar24 to receive messages from airplanes about their location and feed them to their servers.

By placing a Arch Linux ARM root filesystem onto the USB flash drive and installing readsb + fr24feeder, the PlutoSDR can receive, decode and forward ADS-B messages all by itself:

The plutosdr-readsb-fr24feed repository was built, which contains a number of scripts and a CI configuration, to automatically generate USB flash drive images, capable of booting on a stock PlutoSDR. Plugging such a USB drive into any PlutoSDR automatically boots Arch Linux ARM and autostarts readsb and fr24feeder.