RPN hp20s and lcd hp34c proposals


Thanks to those who made possible the project wp34s. I would have contributed myself with something if my knowledge on computing would have been a little above zero :-) but it's not the case. However I have had for years a couple of ideas in my head related to the display and I'd like to mention them now, so you can give your opinion about it.

As everyone knows, the last series made by Hewlett Packard when till independent, the Pioneer, did not include a RPN model with segment lcd screen. That is to say, the RPN models in that serie used matrix screens. In other words, the RPN version of the HP20S was never produced. I noticed it when I was a kid and I bought my first Pioneer.

And this wasnt natural. In fact all the previous spice models had segment(obviously) led displays. So it would have been a logical step to make a simple RPN calculator with segment display, for example the lcd version of the HP34C.

I have problems to work with matrix displays. I love segment displays, which are clear and sharp, and I like simple calculators. I think it would be a good idea, based on the wp34s, to make a RPN model with Segment display by avoiding the use of the matrix section on the screen of the hp30b.
It would cover a niche and the project would be almost straight forward! By this I mean that the layouts are already there: the HP20s and HP34C keyboards. And the manual doesnt need to be written; it was written decades ago: the HP34C manual.

What's your opinion?

jose poyan


But of course the Voyagers were segment and RPN. But I like Pioneers better myself as well.


I know. I was refering to the models with vertical format only.


You might want to repurpose the new 10bii+. It comes with a plain segmented LCD, has the Pioneer keyboard layout, so what would you want more?

Personally, I stick to wp34s. When the firmware is stable, I'll almost certainly will sacrifice a 30b for the purpose.


I thought I read Tim saying it could not be repurposed. But I can't find the post.


Of course it can. The programming connector is the same. There is no JTAG connector for debugging and HP has yet to release technical information but this is not a principal problem.


I don't think there will be any release of anything. The only difference between them (20/30b, 10bII+, 12c) is the screen. Just a LCD table is all you need different.

Personally, I am quite excited there is the ability to build using GCC. We always wanted to get around to that but just didn't have the time.



ATMEL provides the necessary startup files for GCC. I've recently switched to CodeSourcery G++ Lite, the free command line only compiler from them. I have yet to test if this realy works. The code is more compact then with the Yagarto or netX tool chains.

The LCD mapping for the new 12C and 10bii+ units (together with the necessary timing infos, i. e. what to write to the SLCDC controller registers) would be fine.

EDIT: The keyboard arrangement is sufficiently different from the 20b/30b to warrant same explanation, too.

Edited: 29 Apr 2011, 2:03 p.m.


When I've needed to determine a keyboard mapping, I've just used a simple C program to scan the GPIO pins one at a time, drive that pin alternately high and low, and read the other pins to see if any correspond. When a match is found, send the ID of the output and input GPIO pins out the serial port. Then I just press each key in turn and see what comes out.

Similarly for the display, I just sequentially toggle each bit in the LCD bitmap, with a delay (or a wait for a keypress or serial receive), and manually record what segments correspond.


That's a workable idea. The choices are limited as only the WAKEUP pins can be used the way HP designed the software.

For the display, you need to know some details about its physics to be able to configure the number of segments and commons and the corresponding frequencies correctly. Without a JTAG connector, you cannot peek into the settings of the original firmware.


It's not that hard to work out LCD settings by trial and error. There aren't really all that many parameters to adjust, and you don't have to get them all correct to see that you're making progress.

You can use SAM-BA commands over the serial port to write the registers, if you don't want to write a program to do it. See page 175 of the datasheet for the SAM-BA commands. (Prior pages describe how to get into SAM-BA boot mode.)


It's not that hard to work out LCD settings by trial and error. There aren't really all that many parameters to adjust, and you don't have to get them all correct to see that you're making progress.

Exactly. Besides, there's not much variation in hardware between the units.

Possibly Related Threads...
Thread Author Replies Views Last Post
  [PRIME] RPN: another attempt at returning more than one value to the RPN stack Marcus von Cube, Germany 5 1,038 11-05-2013, 02:44 AM
Last Post: Marcus von Cube, Germany
  Vintage HP 15C with bleeding LCD display Michael de Estrada 1 597 10-30-2013, 09:54 AM
Last Post: Jeff O.
  Missing LCD segments (48 SX) Matti Övermark 2 607 09-18-2013, 03:50 PM
Last Post: Matti Övermark
  HP 32s LCD part Trisnadi Sutrisno 2 579 08-27-2013, 02:12 PM
Last Post: Han
  hp 39gii lcd clear question giancarlo 7 1,227 08-18-2013, 07:30 AM
Last Post: Mic
  10BII LCD Repair K Gobeski 0 411 06-19-2013, 08:58 AM
Last Post: K Gobeski
  HP 75d: pale lcd characters Michael Fehlhammer 0 374 02-25-2013, 07:04 AM
Last Post: Michael Fehlhammer
  PCB pictures of a HP10B, HP20S or HP21S? Christoph Giesselink 1 453 12-17-2012, 10:19 PM
Last Post: Randy
  HP 48GX with Black LCD - S/N ID Jeff Kearns 4 738 12-15-2012, 03:55 PM
Last Post: aurelio
  On calculator preservation (LCD darkening, pouches...) Marc Ferrer (France) 4 778 12-04-2012, 08:01 AM
Last Post: Marc Ferrer (France)

Forum Jump: