In the past, RTL-SDR.COM reader JJ has shared with us his LegoPi project, which demonstrated a clever way to enclose a self-contained RTL-SDR build, as well as his multi-feature living room radio build, which combined an RTL-SDR for live radio and an internet-based radio system with MP3 player.
Recently, he submitted to us a new project called 'calcRadio' (information about the calcRadio can be found at the end of the linked page). The calcRadio project consists of a similar self-contained RTL-SDR build as seen in his previous projects (RTL-SDR with speakers and a single-board computer), but this time, it's controlled via an old Casio FX-CG20 calculator. The calculator's interface is programmed in C, and JJ has uploaded his open source code on GitHub.
JJ writes:
The front-end is made of an older CASIO calculator, the fx-CG20, which can be programmed in C thanks to the non-official CASIO SDK: https://github.com/Jonimoose/libfxcg/releases (the fx-CG20 built-in basic language was way too slow).
The back-end is same as last build, a Strong SRT 2023 TV box, flashed with Armbian + Ubuntu and a bash script to handle everything. Under Linux, the Android board is known as Amlogic Meson GXL (S905X) P212 Development Board. It has about the same CPU power as a Raspberry Pi 3 Model B+ but with less power consumption, built-in storage and infrared port.
The key to make it work was the presence of a cloning port on the calculator, which was connected to the UART port on the Android board, allowing serial communication to be established.
