Though I became a HP fan shortly after, my first calculator was actually a TI-1200, a basic calculator with the 4 operations and % with a very nice design. My father's company had given calculators to their best customers, and some had been returned as 'defective'. All it took was to replace the 9V battery and there I had my first calculator.

So just for the fun of it, and in admiration of the equally zen design of the Commodore 7919 (scientific model with just 19 keys), I endeavored to design a Microchip PIC based board for TI-1200 that would convert it to a scientific RPN model.

So here it is: RPN, trig/log/power functions, metric<->US conversions, 4-level stack with LASTX, inpout through a 'command line' with <- capability, 10 memories, store and recall arithmetic, FIX and SCI modes.

The code is written mostly in C (some inline ASM) using the Microchip MPLAB X IDE. The only drawback is that the floating point routines are binary based and the precision is really not good... If anyone has worked on a similar project, or has recommendation / source code for BCD arithmetic and floating point functions in C or PIC assembly, I am definetely interested.

Pictures of the RPN-1200 vs TI-1200 and of the inside of the RPN-1200 are at:

http://www.hpmuseum.org/guest/benoitm/rpn1200.jpg

http://www.hpmuseum.org/guest/benoitm/inside.jpg

Thank you,

Benoit