HP-45 simulator for the HP-20b



#2

In case you are interested, Scott Newell has posted an early version of an HP-45 simulator to the hpwiki. This simulator requires you to overwrite the firmware in your HP-20b, but when finished, you have a pretty cool new calculator in your hands!

Historical note: I believe this is the first successful re-purposing of the HP-20b to act like another HP calculator. Congrats Scott!

Check it out here:

http://hpwiki.fatcity.com/doku.php?id=20b:software-demo_45


#3

Major cool!!!

#4

That's fast work - you could have announced it a couple of days ago so that I could get it into Datafile. ;-)

Still can't even buy a normal 20B over here in the UK yet so no danger whatsoever of re-purposing. :-(

#5

now i want one.


#6

I couldn't tell from the Wiki entry....how much RAM and how much flash does the emulation use; and perhaps more importantly, how much of each remains unused? This might give a handle on how far an effort like this might be able to go with sophisticated scientific or programmable emulators. DEFINITELY a great topic of the HHC2008 conference!

Thanks,

Jake


#7

Quote:
I couldn't tell from the Wiki entry....how much RAM and how much flash does the emulation use; and perhaps more importantly, how much of each remains unused? This might give a handle on how far an

There'a a map file in the tarball, but off hand I think it's using 18kB of the 128kB flash. No idea how much stack is really being used. I'm not sure, but I think you could probably lop off half the current 4kB microcode pretty quickly, as I don't think the 45 uses the full memory map. (Half of it looked blank to me, anyway.)

#8

The number and arrangement of the keys along with the availablity of an emulator could probably make it a 42SII. How to repaint the keys?


#9

No repainting necessary - we'll just need something like the Blanknut. I.e. the numbers, ENTER, and the basic arithmetic operations printed, everything else blank.

However, what we need first is a reasonable LCD (please see previous posts).


#10

I can imagine it takes some good ideas to get along with the limitations of that display. OTOH, replacing it doesn't seem reasonable after what I've read about the keyboard quality. It will remain the worser 42S anyway.

#11

Quote:
[...] we'll just need something like the Blanknut. I.e. the numbers, ENTER, and the basic arithmetic operations printed, everything else blank.
Shouldn't be too difficult to get rid of the paint. It won't resist sanding :-).

#12

Quote:
Shouldn't be too difficult to get rid of the paint. It won't resist sanding :-).
Brutal and feasible. I must admit I had hope for a more elegant method. But that will work for sure ;)
Quote:
I can imagine it takes some good ideas to get along with the limitations of that display.
More than that: the present LCD of the 20b is *forbidding* for a menu system based on soft keys. However, such a system is state of the art.
Quote:
OTOH, replacing it doesn't seem reasonable after what I've read about the keyboard quality. It will remain the worse 42S anyway.

True. But it may demonstrate the opportunities -- one working model is worth a thousand words.

#13

Quote:

True. But it may demonstrate the opportunities -- one working model is worth a thousand words.


Hate to throw cold water here, but I'm not sure the 42S is a feasible candidate.

First, the display is radically different. Even if you were to somehow transplant hardware from a donor calc, the CPU doesn't have enough lines to drive more than 400 LCD segments--the HP20B is maxed out. If you're going to replace the display and add a driver, you might as well start from scratch with a new PCB design.

Doesn't the 42S contain 8kB of RAM? That's 2kB more than what we have to work with on the 20B, and there's going to be some overhead in the simulation. Could you even run a simulated 42S with 2k or 4k? Sure, you might add RAM with the internal GPIO pads, but now you're targeting not only people who can re-program the 20B, but those that are willing to open it and perform surface mount surgery.

How large is the 42S ROM? I've seen mention of 64k, but I'm not sure if that's words or bytes. If bytes, you might squeeze it in. If words, well, there goes your entire flash just to hold the simulated ROM. Adding memory is an option--see above.

To me, the keypad is the only bright spot--the layout appears to be a match in many respects.

I'm not even going to bother researching the 42S (CPU speed? legal status of firmware image?) until a viable display workaround pops up.


#14

I've watched this thread with amusement. IMHO, repurposing the 20B as a 45, 41, or 42 lacks imagination. Instead of trying to shove an existing calculator personality in there, why not take advantage of this unique platform and try to create something new, something better. The 42 if possible (and that s a big if) would be too awkward. Get a PDA and run Free42. The 41 would need some sort of base modules (e.g. Advantage) because of the lack of I/O. IIRC the Advantage ROM is 24K. It's going to be tight and again awkward.

I think you have enough keys to make a very nice 32SII like machine with enhanced capabilities (i.e. the dox matrix display). Instead of creating an emulator + ROM, start from scratch, and if you need code (solver, matrix, complex numbers, etc...), then look to Free42.

Clear advantages to this would be:

  1. Better battery life.
  2. Increased speed.
  3. A platform others can build on to make it just their way.
  4. Increased possibility of creating something that many would want (a small, cheap, disposable, RPN, programmable, scientific).
Lastly my experience with calculators emulating calculators has been poor. Documentation does not match the keymap. The keymap doesn't match the keyboard. It can be acceptable as an execution platform, but for daily use, it can be frustrating.

#15

Documentation does not match the keymap.

As there aren't a lot of calculator emulators for calculators out there, I would like to know what emulators are you talking about and what mismatch between documentation and keymap did you notice (so the documentation can be fixed).

The keymap doesn't match the keyboard.

I don't really understand what do you mean by this. Do you mean "the keymap of the emulated calculator doesn't match the keyboard of the emulating calculator" or what?

It can be acceptable as an execution platform, but for daily use, it can be frustrating.

I am using calculator emulators for calculators on a daily basis for the last 10 years - no frustration noticed.

Edited: 12 Aug 2008, 2:06 a.m.


#16

I've have used 41 emulation on the 71B (HP), the 48GX (your's and HP's), and the 50g (yours).

The documentation I refer to is any 41 documentation. It will not match the emulator because the keyboards are different. I find this frustrating for programming and general use. IMHO, the purpose of the 41 emulators for the 71B and the 48GX from HP were to allow an investment in 41 code to be extended, but not as a long term 41 replacement.


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