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HP 20b biz calc can be modded

HP 20b biz calc can be modded

Make Pt0926
A few makers sent this in… the latest HP 20b biz calc can be modded’ (they’re releasing a dev kit). I downloaded the dev kit, they’re not messing around, schematic is included. Gang, this is an Atmel ARM, an LCD with the power supply done – what the heck is going on here? Way over powered for a calc, just asking for projects – Makers please do something cool with this!

22 thoughts on “HP 20b biz calc can be modded

  1. japroach says:

    Small correction, this is an Atmel ARM, not an AVR. AVR = tiny, mega, xmega, etc.

  2. Darren says:

    All in a $40 dollar calculator. Wow! HP gets their mojo back.

  3. Thinkerer says:

    Not only HP’s mojo but their cred and it’s overdue.

    Reading through the documents, one gets the sense that a tinkerer is at the helm of this idea. Backtracking the name and Email address listed in the documentation outs the head of R & D for Hewlett-Packard, Cyrille de Brebisson as the hero behind getting this out of the corporate murk:

    Wouldn’t it be great if every widget maker were this amenable to messing around with their products?

  4. anachrocomputer says:

    HP may have made a snazzy bit of kit here, but it’s not RPN! Oh, wait, how about a mod that turns the “=” key into “Enter” and makes it calculate the way that a proper HP would do! With the stack, and the postfix notation…

  5. Simon says:

    Since the interesting links are missing in the article:

    Developer Kit download:

    Wiki for the HP 20b repurposing project:

    And – to complain – of course the Calculator has a pricing point of 55 EUR in Europe. Which currently is twice the price as in the US :-(

    Have fun,

  6. anachrocomputer says:

    I take it all back — the HP 20B has an RPN mode, described by HP as “time-saving RPN”. Yes, HP is back in the calculator business. Now, I wonder if the PCB is gold-plated all over, like they used to be? And I wonder if it can work in hex?

  7. Wilson! says:

    It’d be a lot cooler if it were a “landscape” form-factor, like the old HP 12c and its ilk (like the mid-1980s HP 15c I had back in the day.

  8. says:

    I’m catching the link to HP’s product page but I’m missing the link to modification info. Any help? Training wheels?

    Also let me second anachrocomputer’s comment. I just got a new HP-35s. HP calculators are back. I’d love to know if the same mods will be practical for the 20B’s similar-looking bigger cousin.

  9. Windell Oskay says:

    I can’t help but wish that it were starting out as a scientific calculator– I’m not sure that I’d want to be seen with a business calc! :P

    But… 30 MHz AT91SAM7 and 9 months battery life on two CR2032s… wow. My old HP48SX graphing calculator– no slouch at the time– had a 2 MHz 4-bit CPU. This thing is a monster!

    Now, the *real* test of whether it’s mod-able is the construction. Many classic HP calcs were molded shut and could only be destructively opened. Anyone know?

  10. Jason says:

    To answer the last posters question:

    The user manual for the device talks about opening the calculator case. There’s also a programming (JTAG) header in the schematic, and the developer kit has all the source code for the ROM.

    Looks like your covered. =)

  11. pedant says:

    Looks like his covered what?

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