Changing the ROM of a HP-35s?
#1

Hello,

Do you think it would be technically possible to change the ROM of a HP-35s?

The hardware of this machine rocks! Nice keys, low battery consumption, alphanumeric LCD, beautiful looks. The software on it is OK but is a bit disappointing imho. I think there should be more potential with this CPU and 30k memory. Like, for example, outputting '-1' instead of 'error' when pressing x^2 button if 'i' is on screen.

Is this ROM located under the same epoxy blob as the CPU? Is such a type of ROM typically modifiable somehow, and if it's truly hardwired read only, to replace it with something else somehow? I have much more software than electronics experience. It would be awesome to learn programming assembly for this CPU (or if there's a compiler for it it's even better) and applying this to the actual device to use it.

It would be fantastic to come up with something that uses roughly the same key layout but is better, and to have the ability to upload ROMs to it with USB from any OS including Linux.

Thanks.


Edited: 2 July 2011, 2:57 p.m.

#2

Quote:
Is this ROM located under the same epoxy blob as the CPU?

I'm afraid so. As far as I know, the ROM is on the CPU chip and is mask prommed. No chance to update anything here.
#3

Quote:
It would be fantastic to come up with something that uses roughly the same key layout but is better

This was the basic idea we started our WP 34S project with 8-) after ranting many months about HP unwilling to come out with a scientific successor of the 42S. AFAIK, the 20b, 30b, and 12C are the only HP calcs allowing to be repurposed in any way by educated users. And the 10bii and 50g are as well. Developer's tool kits are available for the 20b, 30b, 12C. That's it, but that's far better than nothing :-)

Of those three, the 20b and 30b sport the most versatile display (and they share the same processor), and the 12C and 30b feature the best keyboards. The intersection is the 30b suiting best to be repurposed for the time being.

Walter

Added the italic text above taking care of Tim's and Pauli's remarks posted below.


Edited: 3 July 2011, 4:21 p.m. after one or more responses were posted

#4

Quote:
AFAIK, the 20b, 30b, and 12C are the only HP calcs allowing to be repurposed in any way by educated users.

The 12C, too?

Interesting, is there any development system available for it?

Franz

#5

Hi,

See my rather tongue-in-cheek reply to the OP in this thread ;-):
http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/archv019.cgi?read=161995

#6

10bII+ as well.

TW

#7

I don't know any reason why one couldn't do the same kinds of things with a 50g. Like the 12C, 20b, 30b, and 10bii, its firmware is in flash memory. It uses a Samsung S3C2410 SoC with an ARM 9 core.

#8

This is definitely possible. Without erasing the existing calculator functionality too. My 49g+ died so it won't be me.


- Pauli

#9

I'd love for the 35s to be reprogrammable. Lots of RAM, nice keyboard, heaps of flash and a good display. The 34s functionality would pale in comparison to what could be done with this platform.

Sadly, not to be.

As it is the 34s pretty much does everything the 35s does except algebraic support and lots of RAM.


- Pauli

#10

Not so nice keyboard IMHO: the cursor cross is located one row too high :-( Else six softkeys would have been feasible. Oh HP, why did you do this? You (did?) know better!

Walter

#11

OK, for those needing a really big stick for hunting, the 50g might be appropriate. Personally, I prefer smaller weapons ;-) But a REASONABLE DISPLAY will be nice, of course d:-)

Walter

P.S.: Strange, but it seems to me we had this discussion more than once before. Presumably getting old d;-)



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