Embedded programs developer Anders Nielsen has constructed a software-defined radio (SDR) with a distinction: it is powered by the venerable MOS Expertise 6502 eight-bit microprocessor, first launched in 1975.
“This little eight-bit CPU powered the Apple I & II, Commodore 64, Atari consoles, and even the [Nintendo] NES,” Nielsen writes of the chip, which turned 50 final week. “For a lot of, it was the chip that launched the world to inexpensive private computing. And now, half a century later, it is again — this time operating the entrance finish of my do-it-yourself SDR. Consider an SDR because the Swiss Military knife of radios. As an alternative of filling a workbench with devoted gadgets, like a storage door opener, a satellite tv for pc receiver, and a shortwave set, you simply plug in an SDR and let software program do the heavy lifting. Tuning, filtering, demodulating is all dealt with by code.”
Dubbed the PhaseLoom, Nielsen’s SDR is predicated on a quadrature sampling detector design, with a low-pass filter to cut back noise and a neighborhood oscillator generated by a Skyworks Options SI5351 clock chip — below the management of MOS Expertise’s basic 6502 processor, operating an meeting program written by Nielsen as proof you do not want a robust processor or field-programmable gate array (FPGA) to run a easy software-defined radio.
“After I first powered it up, I wasn’t certain what to anticipate. However certain sufficient, with an antenna connected, I may tune into the 40-meter ham band,” Nielsen says. “It is tough, noisy, and really a lot a prototype — but it surely works. A 6502-powered SDR is alive. Most SDRs right this moment depend on highly effective trendy processors or FPGAs. Operating one from a CPU designed in 1975 is totally ridiculous — and that’s precisely why it is so enjoyable. The 6502 might not be doing the heavy DSP [Digital Signal Processing] (but), but it surely’s orchestrating the entire present. And with extra improvement, I plan to push it additional — possibly even squeezing in some actual sign processing routines on that historic silicon.”
The 6502 drives the PhaseLoom by means of a program written in meeting — although it is hosted on a separate board, the 65duino. (📷: Anders Nielsen)
Extra info on the challenge is out there on Nielsen’s weblog, whereas KiCad challenge information and GNU Radio flowgraphs have been printed to GitHub below an unspecified open supply license; supply code is out there within the separate 65uino repository, a 6502-based single-board pc that’s required to make use of the PhaseLoom. Nielsen has additionally launched fully-assembled boards, which embody a hand-soldered “bodge wire” board design repair, on his retailer at €55.20 (round $65) — although you may additionally want a 65uino, which can set you again a further €18.29 (round $21.50) plus further part prices for the CPU, IO chip, ROM, and miscellaneous components.
