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HP35s repurposing
10-10-2019, 08:57 AM
Post: #1
HP35s repurposing
Is it possible to repurpose the HP35s in a way similar to 20b/30b?
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10-10-2019, 10:41 AM
Post: #2
RE: HP35s repurposing
(10-10-2019 08:57 AM)Marco Polo Wrote:  Is it possible to repurpose the HP35s in a way similar to 20b/30b?

No.

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    Massimo

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10-10-2019, 11:39 AM
Post: #3
RE: HP35s repurposing
(10-10-2019 10:41 AM)Massimo Gnerucci Wrote:  No.

So bad.
It would have been a nice chance to use a decent hardware with better firmware.
Is it an hardware limitation?
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10-10-2019, 12:31 PM (This post was last modified: 10-10-2019 12:33 PM by Sadsilence.)
Post: #4
RE: HP35s repurposing
(10-10-2019 11:39 AM)Marco Polo Wrote:  So bad.
It would have been a nice chance to use a decent hardware with better firmware.
Is it an hardware limitation?

HP20B and as a consequence it's hardware twin HP30B was a "gift" from HP. A general purpose development platform to realize own (calculator) ideas. Programming interface, curcuit schemes, documentation and and and were offered (for free). All in all a nice microcontroller demo board back in 2008 for a nice price. "Incidentally" HP showed, that platform can be base for a calculator.

Totally different approach for HP35s: Closed system, difficult to open, zero inside informations from HP. It is "only" what it is: a 21th century HP35.
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10-10-2019, 05:15 PM
Post: #5
RE: HP35s repurposing
(10-10-2019 11:39 AM)Marco Polo Wrote:  
(10-10-2019 10:41 AM)Massimo Gnerucci Wrote:  No.

So bad.
It would have been a nice chance to use a decent hardware with better firmware.
Is it an hardware limitation?

The 35S doesn't have flash ROM, so reprogramming it would require replacing either the ROM chip or the whole PCB.
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10-15-2019, 06:49 PM (This post was last modified: 10-15-2019 06:50 PM by jklsadf.)
Post: #6
RE: HP35s repurposing
I've looked into it before, but from the teardown pictures, the main processor is under an epoxy blob http://www.finetune.co.jp/~lyuka/interests/calc/hp35s/

The main processor uses a masked ROM, for cheaper manufacturing, and doesn't have any reprogrammable flash. From what I read, it was designed completely by Kinpo, and HP doesn't even have the source code for the firmware. Repurposing the HP 35s would likely involve replacing the entire PCB, and wouldn't be worth it. The most difficult part would probably be the connector to the LCD.

The only HP (non-graphing) calculators which are easily reprogrammable are their most recent ones, all of which happen to be financial models:
  • hp 20b
  • hp 30b
  • hp 12c (both of the new versions using arm processors)
  • hp 10bii+

All of the following calculators, although relatively new, are Kinpo designs with a non-reprogrammable mask ROM:
  • hp 33s
  • hp 35s
  • hp 17bii+
Which is unfortunate, because these calculators also have the best LCDs.
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10-15-2019, 07:19 PM
Post: #7
RE: HP35s repurposing
Is it possible to repurpose it like the Panamatik woodstock brain transplants? After all, the 35s display and keyboard are pretty nice.
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10-15-2019, 07:33 PM
Post: #8
RE: HP35s repurposing
It'd be possible if you replaced the entire PCB, but again I think it'd be a huge pain because of the LCD connector. There's no built in controller chip on the LCD, and if you look at the teardown pictures there's like a bajillion connections going to the (extremely fine pitch) LCD connector.
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Yesterday, 01:33 PM
Post: #9
RE: HP35s repurposing
(10-15-2019 07:19 PM)David Hayden Wrote:  Is it possible to repurpose it like the Panamatik woodstock brain transplants? After all, the 35s display and keyboard are pretty nice.

Yeah - THAT would have made a really nice WP34S-ish platform :-)
Jake
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Yesterday, 04:42 PM
Post: #10
RE: HP35s repurposing
A couple of guys have mentioned that the 35s has a nice display.

Really? That caught me off guard. I think it's horrid frankly, an ugly matrix of oddly-spaced characters. To me it's one of the machine's weaker aspects.

I greatly prefer the dual-line display on the WP34s, oops I mean HP30b. I guess it is fortunate for me that is the reflashable one!
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