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Olimex Shows Off the Compact, Low

Jul 13, 2023

Bulgarian open-source hardware specialist Olimex has begun testing of an low-cost single-board computer built around MOS Technology's iconic 6502 microprocessor, the Neo6502 — using a Raspberry Pi RP2040 microcontroller to keep the device compact and affordable.

"Finally we managed to build few prototypes for tests," Olimex founded Tsvetan Usunov writes of his work on the Neo6502 project. "The delay was caused by components supply problems for the new components in these boards which we do not stock. Anyway the new shiny purple color prototypes are assembled and this weekend I will have fun."

Usunov first teased the concept for the Neo6502 back in April, confessing to "a sentiment for retro computers." The stated goal at the time: building a single-board computer with a MOS 6502 at its heart, for as low a cost as possible — and using a Raspberry Pi RP2040 microcontroller to stand in for multiple other expensive chips which would otherwise be required to complete the design.

The prototype shown off by Usunov this week is based on the Western Design Center (WDC) W65C02S, a modern surface-mount processor designed to be compatible with the original MOS 6502 but in ready supply and taking up considerably less room. The remainder of the board is surprisingly light on integrated circuits, thanks to the Raspberry Pi RP2040 taking over tasks like peripheral control and memory provision: there's the RP2040, of course, and three buffer chips, plus 2MB of flash storage.

Elsewhere on the board is a piezoelectric buzzer, which can be enabled and disabled with a physical jumper, a 3.5mm analog audio output, a USB 2.0 Type-A Host port for a keyboard, an HDMI port carrying a DVI signal for connection to a display, a connector for accessing the 6502's hardware bus, and a UEXT connector for solderless expansion to external hardware over SPI, I2C, or UART buses.

"When these will be available for sale now depends on how quick we can develop the firmware for RP2040 and W65C02," Usunov explains. "If you think you could contribute to this project you are welcome to join! Send me email to info at olimex dot com and tell me how you want to help."

More information on the project is available on the Olimex blog; pricing has not yet been set.