JJ's calcRADIO Uses a Casio Programmable Calculator as a Software-Defined Radio User Interface
What can you do when your portable SDR setup lacks a display and keyboard? Connect a Casio to its UART bus, of course.
Mononymous maker JJ has designed a portable software-defined radio, complete with MP3 playback support, unlike any other: its user interface is a repurposed Casio calculator, creating what they call the calcRADIO.
"I recently challenged myself to build a radio without buying anything, just recycling some old parts I had in my toolbox," JJ explains of the project's origin. "So I came up with the calcRADIO! A standalone, portable, FM / DAB+ / INTERNET / MP3 radio. The user interface, both for input and output, is made of a Casio fx-CG20 graphical calculator (also compatible with the fx-CG10 and fx-CG50) and it runs all day non-stop on a 5V / 18000 mAh power-bank."
The calcRADIO, brought to our attention by RTL-SDR.com, has at its heart a low-cost receive-only RTL-SDR software-defined radio dongle connected to a Strong SRT 2023 single-board computer — originally designed for use as an Android set-top box, but reflashed by JJ with Ubuntu Linux and given amplified analog audio capabilities with a cheap USB soundcard. Together with the power bank, and housed somewhat haphazardly in an off-brand Tupperware, that's enough for the radio side of the equation — but not the user interface.
Rather than adding a keyboard and screen, which would bulk the project out, JJ opted to repurpose a programmable calculator: the Casio fx-CG20. "This calculator is great because (1) it has a three-wire serial port built-in that is used to clone two calculators together, so I can use it to connect to the UART port on my Strong SRT 2023 Android board," JJ explains. "and (2) this calculator can be programmed in C with the non-official Casio SDK [Software Development Kit]. Finally (3) it has a beautiful color display and I can even play games while listening to the news!"
More information on the project is available on JJ's homepage, towards the bottom; the source code has been published to GitHub under an unspecified license.