This wiki was originally created to be a development home for repurposing the HP-20b calculator, but has since grown to support several repurposing projects. It is our hope that this grass-roots approach to calculator hacking will expand to include other many HP calculator models and open-source projects.

A Hewlett Packard Infrared Signal Decoder
Martin Hepperle
June 2015
Several Hewlett Packard pocket calculators are able to send printer output via Infra-Red (IR) signals to a small portable printer. They use an HP-specific transmission protocol which is also called “Red Eye”. This protocol is different from the better known IrDA protocol. This document gives a brief overview of the format and describes hard- and software to build a decoder system for this protocol.
This system allows receiving the “Red Eye” signals with a computer via a serial or an USB interface.

Links and recommendations for books about astronomical algorithms.

The world's smallest programmable RPN calculators ever. The complete family DM-11, DM-12, DM-15 and DM-16.

Web-based simulator of the hp15c calculator. Enhanced version with stack display. Note that contrary to emulators such as nonpareil, this simulator does not produce the same results as the real hp15c.

Might be useful when disassembling an HP28.

Some pictures and text about opening an HP 28S.

The famous HP journal is available on-line at last!

Some issues of the famous HP Journal are available on-line.