Atmel ARM7 LCD driver: alphanumeric display


As already discussed, using the Atmel ARM7 cpu in the voyager line opens the exciting possibility to resurrect the beloved hp 15c. The largest limitation of the machine would be, as was in 1982, the simple 10 characters numeric display: I would like to discuss [again] about using the 400 pixel display driver of the cpu to control an alphanumeric display.

With a 5x7 dot matrix design, we could get one line of 10 characters with dots/commas (370px) plus 30 annunciators: probably, only 10 characters are not very suitable for complex number handling, equations editing or soft menu implementation.

With a 14 segments design, we could get up to two lines of 12 characters each with dots/commas (384px) plus 16 annunciators: quite good, but the dimensions of the voyager case (without any redesign) fits better a single line display. Furthermore, segmented displays are quite limited in font set.

I propose here an hybrid 5x5 "quasi" dot-matrix design, on which we could fit one line of 14 characters with dots/commas (378px) plus 22 annunciators. This design is probably not original, but I am not able to remeber where I saw it (maybe a VCR, dvd player or car audio display...).
Here you see the configuration of the character matrix, a proposed character set and a picture of an hp 15c (original picture from the Museum, by Dave Hicks) showing an equation.
It has already been discussed about the availability of large dot matrix displays with integrated driver chip (like on the Smartcalc 300s), but consider the dimensions constraints to fit a voyager case.

Comments are welcome!


Are you talking about a real hardware PCB upgrade?, or just dreaming about something you would like HP to do?

If you are talking about a real hardware upgrade then details have been discussed a fair bit before for a 15C. From memory a suitable 2 line by 40 character display was looked at. And from my recent uWatch2 LCD investigations, there would likely be more options available.

Replacing a 10 character segment display with a single line 14 character dot matrix display isn't much of an upgrade IMO. Any hardware upgrade would ditch the built-in ARM LCD driver for sure.



Are you talking about a real hardware PCB upgrade?, or just dreaming about something you would like HP to do?

My guess. Dreaming. That display would imply added functions, so a different calculator and a different case to leverage the added functions. It would have limited use with existing ROM images. But for a new calculator I like it, but I prefer the flexibility of a regular dot-matrix. Take the existing 35s. The dot-matrix display is not contiguous limiting the possibility of a 42S style menu system.

If I were to build a fantasy calculator with limited new stuff, then I'd start with the existing 17BII+ display. It has all the announcers you'll need and has a contiguous dot-matrix display.

If I wanted something a bit larger, then start with any 48/49/50 series display. Both the 17BII+ and 48-50 displays are still being manufactured. Unsure how you'd get such a display outside of HP.


He's talking about what could be done with the new AT91SAM7L128-based 12C platform, by only replacing the display glass. (Well, the display glass would have more electrical contacts, so the PCB layout would have to be revised too.)

The point is that HP is standardizing on the AT91SAM7L128 for midrange calculators, so they're more likely to do build new products that don't require a separate LCD driver chip.


Right, Eric: my investigation was about replacing the only display glass, which will obviously require a PCB revision.
No other hardware or physical changes (add lcd drivers or change case dimensions to fit larger displays), unless keytop labels.
I think this would be a viable industrial way to get a modern small calculator.

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