Alex Garza's PX41CX Is a Build-It-Yourself Homage to Hewlett-Packard's Classic HP-41CX

Vintage calculator enthusiast Alex Garza has designed a modernized clone of the Hewlett-Packard 41CX (HP-41CX), buildable from a kit using only through-hole parts and boasting a microcontroller heart configurable from 8MHz to a blistering 32MHz.

"PX41CX [is] a modern tribute to the legendary HP-41CX," Garza explains of the machine. "Experience the fun and educational journey of building your own calculator with […] a faithful reproduction of the renowned HP41CX. This DIY project offers an engaging, educational experience for electronics enthusiasts and calculator aficionados alike."

The calculator is designed to replicate the functionality of the Hewlett-Packard 41CX, the last entry in the HP-41 range. Launched in 1983, four years after the original HP-41C, the HP-41CX offered extended memory and an integrated time-keeping module — both of which have been carried over to the PX41CX.

Rather than using now-scarce original parts, the PX41CX relies on emulation — running a faithful recreation of HP's original calculator on a single Microchip AVR128DA microcontroller. This can be configured to run from 8MHz to 32MHz, and at either end of the speed scale easily bests original hardware for performance. The emulation includes the full internal RAM with 319 registers and a full complement of expanded RAM with 600 registers, the ability to store up to 12 4k ROM modules. a real-time clock, and RS232 connectivity over a USB mini-B connector.

Other advantages over HP's original include a larger 250×122 bitmap display, an enhanced timer that boosts the resolution, and the option to power the device from a CR2032 button-cell battery for use on-the-go or via the USB connector for desktop operation.

More information on the kit is available on Garza's website, while the hardware itself is listed on Tindie at $115 — though, at the time of writing, was showing as out-of-stock.