RPN1200 (with pictures)  Printable Version + HP Forums (https://archived.hpcalc.org/museumforum) + Forum: HP Museum Forums (https://archived.hpcalc.org/museumforum/forum1.html) + Forum: Old HP Forum Archives (https://archived.hpcalc.org/museumforum/forum2.html) + Thread: RPN1200 (with pictures) (/thread248965.html) 
RPN1200 (with pictures)  Benoit Maag  08272013 Though I became a HP fan shortly after, my first calculator was actually a TI1200, 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 TI1200 that would convert it to a scientific RPN model. So here it is: RPN, trig/log/power functions, metric<>US conversions, 4level 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 RPN1200 vs TI1200 and of the inside of the RPN1200 are at:
http://www.hpmuseum.org/guest/benoitm/rpn1200.jpg Thank you,
Benoit
Re: RPN1200 (with pictures)  Katie Wasserman  08272013 Very nice. I did something very similar with an HP25 that had a totally corroded PCB and bad chips. I gutted it and used a single SX28 chip to scan the keyboard and drive the display. This chip has very pretty limited RAM and ROM (128 bytes/2K bytes), so I only put in long (16 digit) integer functions.
Re: RPN1200 (with pictures)  Benoit Maag  08272013 Hi Katie, Thank you for your feedback. Packing everything in the HP25 must have been very hard  there is almost no space! The RPN1200 is based on a Microchip PIC 18F2550 with 32kwords of program flash (about half of which is used), and the display is driven by a MAX7219. I tried to use a PIC 16F88 which is a simpler chip but the 4k of flash were not enough for floating point operations... In any case, what I learned through the project is that making a calculator is not easy... Benoit
Re: RPN1200 (with pictures)  Geir Isene  08272013 This is just plain crazy ;)
Awesome stuff.
Re: RPN1200 (with pictures)  Nigel J Dowrick  08272013 You should probably look at the source code for the WP34S. The calculation routines in this are based on the decnumber C library, which represents numbers in a packed decimal form and allows a range of precisions. The WP34S firmware takes up about 118 kB when compiled which is a lot more space than you have available, but the WP34S does much more than your calculator does, so perhaps the decnumber routines could be made to fit?
Nigel (UK)
Re: RPN1200 (with pictures)  Nigel J Dowrick  08272013 I forgot to say: your calculator looks absolutely amazing!
Nigel (UK)
Re: RPN1200 (with pictures)  Thomas Klemm  08272013 I hate to be that guy but I miss the doublewide ENTER key. On a serious note: very cool calculator!
Cheers Re: RPN1200 (with pictures)  Steve Simpkin  08272013 Very cool conversion! Re: RPN1200 (with pictures)  Egan Ford  08272013 That is awesome. You did the right thing. You saved a 1200 from itself. :)
Re: RPN1200 (with pictures)  db (martinez, ca.)  08272013 incredible
Re: RPN1200 (with pictures)  Benoit Maag  08282013 All,
Nigel, Re: RPN1200 (with pictures)  Eddie W. Shore  08282013 The RPN 1200 looks nice  great job with the conversion!
Re: RPN1200 (with pictures)  Matt Agajanian  09022013 And this even surpasses that Sinclair Scientific!!! Besides, full 10+2 digit display as well as at least 12digit accuracy. Excellent and stylish too!
