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I have been actively following the 15c ressurection threads around here and have a solution I would like to toss out. The OpenRPN project seems to be generally well recieved by the community and is a joy to manage... still, I'm always looking for ways to stir up more mischief:

The 10c form factor is still being produced by HP, and 12c's are readily available for a relatively low cost (less than 15c's to be sure). If a few people feel like taking on the task of reverse engineering the current 12c and creating a 15c ROM emulator for it we may just have a cheap and dirty solution on our hands.

Sure, this may not be a *perfect* solution. I think there may be a few LCD indicators missing. But if you can reach 99% of 15c functionality for under $100 who's going to complain. As for the keytops and overlay, we are developing a system for etching them using a commercial laser cutter as part of the OpenRPN project.

I don't have enough time to personally manage such a project, but I would be happy to provide assistance and perhaps take on doing production runs.

Comments?

Best Regards,

Hugh Evans
OpenRPN Project Manager

Where is Chris Woodhouse? What does he think!

I think I remember Nelson suggesting that he would try this, once the 15c ROM is extracted?

Regards,


Bill

I'd suggest the CPU+ROM replacement with a small "dauther" board with one MSP430F449 from TI running an emulator with the 15C ROM inside it. This chip has LCD controller also and runs from 1.8V to 3.6V directly.

Indeed I have plans to do that (I already have some MSP430s) but I don't have much time now (nor $$$...).

I think that Erik Smith has done good progress on the reverse engineering of the Voyagers (ROMs and CPU emulation).

Best regards,

Nelson

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Where is Chris Woodhouse? What does he think!

Well I think it is a great idea and something I am both willing and have the time to work on. However, I don't really know where to start. I have lots of programming experience and I am even relatively familiar with assembly, but only on an x86 machine. I have never worked with embedded stuff and the extent of my electronics experience is making a siren from two 555 timer/oscillators and that was back in high school. If someone is willing to help me get started I would love to work on this.

Chris W

Isn't the modern 12C rom combined with the processor, surface mounted under a blob of resin/plastic? How would you extract the ROM from the 12C and wire in a replacement when there is no socket or pads for it on the board?

Hi, Bruce;

you're right about the new Platinum, but I am not sure if the "flat" HP12C has the same construction. Newer HP12C produced in China (single 3Vcc battery units) still use "classic" SMT assy (wow! Have I lived enough to consider SMT as a classic technology or are new technologies dying into obsolescence too young?), so all terminals/pads to access both keyboard and LCD are still there. In these units there is ony one chip, so your concerns are right about ROM access. I'm not sure about new HP12C models after the HP12C Platinum wasintroduced; are they following the same "blob" scheme?

I know there are at least a few people hacking at voyagers. All of what I have seen involves the original machines, though.

What I would propose is to dissect one of the current production 12c's. If it does have a bubble of resin, try some of the following:

If you can afford it, have an x-ray taken of the machine. This will give you some idea of what is under that blob.

Get some dental tools and carefully clean the resin off (it's labor intensive, but will be worth the effort).

Once you find out how the machine is layed out, it may be as simple as soldering in a new memory chip to change the ROM.

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Once you find out how the machine is layed out, it may be as simple as soldering in a new memory chip to change the ROM.

The 12C has only had a single chip for quite a while now. Even if they've moved to chip-on-board (blob) assembly, there's still only going to be one chip.

Does that mean the 12C to 15C conversion project is DOA?

Chris W

Just that you have to replace one chip.

Even if the new 12C ones has only one chip, the replacement will be on another PCB attached to the main PCB without the original chip. This new PCB must have a NEW CPU/ROM combination - I'd suggest the MSP430F449 from TI, that works fine with the 3V coin battery cell, has LCD interface, 60KB of FLASH ROM and 2KB of SRAM, serial/I2C/SPI interfaces. This chip must be programmed with a NUT CPU emulator, then you can download on it any of the Voyagers' ROMs.

I have one "semi-dead" HP-11C that I'm planning on do that, I have the MSP430 ones, and the Voyagers' case has space even for a SD/MMC card interface on the side.

I have only 2 thinks to do:

1) build a replacement PCB (costs $$$, at least US$30 from www.olimex.com)
2) Build a NUT emulator to run on the MSP430

Anyone else interested on this idea?

Best regards,

Nelson

Why not try to find out what chip HP is using? AFAIK the ACO redesigned the 12c into it's current incarantion, in which case you may be able to pry an answer out of a hydrix employee.

If the chip is something that can be aquired without much difficulty, I would not hesistate to just replace it and leave the rest of the board intact. Why spend $30+ when you could cut it down to a few $$$ instead?

If a new PCB, etc. is the goal I would lean towards some sort of OpenRPN "lite." Where a replacement board can be dropped in place of the original but lack the extra forms of I/O and expandability. The only reason I would propose this is so that not much effort is used by two projects with very similar goals.

I say find out what's running the thing and if you can source the parts. Perhaps even HP would sell a few chips if you ask nicely.

Best Regards,

Hugh Evans
OpenRPN Project Manager

Quote:
Why not try to find out what chip HP is using?

AFAIK, it's still the 2AF1-0001 chip, manufactured by
Agilent.

Quote:
If the chip is something that can be aquired without much difficulty, I would not hesistate to just replace it and leave the rest of the board intact.

What good does that accomplish? If you do that, you've taken a perfectly good HP-12C, and turned it into... [tada!] an HP-12C. Not very exciting, IMNSHO.

Quote:
Perhaps even HP would sell a few chips if you ask nicely.

Yes, I know for a fact that HP will sell you the chips. They are available through all the usual HP resellers such as Office Depot. They will cost you approximately $70 each. The good news is that you get a bunch of other parts with the chips, at no extra charge!

Here's one attached to the current spare parts kit:

You're right. My mistake: I was thinking of the Platinum's.

Here is a picture of the insides of a modern 12C. No blobs in site but still a single chip.

Here is my point again: as you cannot replaced its INTERNAL ROM, is much easyer to build a small header board with one MSP430F449 like this one, take the original chip off, rewire the LCD/keyboard/power connections and - voilĂ ! A new platform to do whatever calculator you think of with 60KB of assembler 16 bits routines of MSP430... with even 2K of SRAM, and with the very low power of the MSP430 the battery could last for years...

This is why i'm excited about: it is easy, and I think that $23.95 isn't too expensive to do that (plus $9.95 of the JTAG adaptor).

As this can be a side project from OpenRPN, this can be faster and cheaper to start the hardware/software development.

Of course, one can build another PCB with a discrete LCD controller (like the I2C ones from Philips) and a small LPC2106 (or LPC2214 with external memory bus) ARM based microcontroller on it do to the ARM version of the calculator.

Best regards,

Nelson

This sounds like an excellent plan to me. I think we can pull this off by using a portion of the OpenRPN hardware (CPU and memory). At moderate production volumes we could get the ppu around $10.

That said, would anyone here pay under $100 for a brand new 15c? :-)

Hi, Bruce;

thanks! Your picture is perfect!

This is the same internals of the last HP12C before the HP12C Platinum. I thought they would change the HP12C to follow the Platinum internals, but I see that this was not done. Strange... why not to use these internals and add the new processor only? Well, forgive me: I forgot that the Platinum needs ALG versus RPN "extra" annunciators, so... "why not to design a new one?" And I guess that keeping the earlier HP12C design also means "Don't touch it!!"

Cheers.

Luiz (Brazil)

Edited: 20 July 2004, 11:51 a.m.

... is there any chance that some "extra featues" are added? (memory+, 14-segment LCD, etc.) I know it means extensive SW changing, but... why not to ask?

Cheers.

Luiz (Brazil)

I think that the LCD must be the original, I don't know any of-the-shelf LCD display of the same size of the Voyager's. I found some COG character modules that *almost* fit inside the case, but you'll need to "shape" the case accordingly. I'm planning a entire PCB replacement with only one chip - CPU from TI (MSP430F449, with segment LCD controller) and maybe one RS-232 level converter, all operated with the same 3V coin cell of the China made 12Cs.

About the software, as it has FLASH ROM, you can run an emulation OR any other modification you want on the original ROM (more ROM up to 32K(??), more RAM up to 1KB+1KB for the system) or any other software you want on it - even with realtime clock. The battery can lasts years with one of those MSP430 from TI, search for its datasheet to see its (very) low power needs... This CPU costs < US$15 on the market.

I only need one these new HP-12C to "play" with - I'll not sacrifice my USA made flex-PCB near-mint 12C!! It only need to have a case/keyboard and LCD intact, the CPU can be "toasted" ;)

I'll try to do it first with one prototype header PCB for the CPU and manually wired on the LCD/keyboard contacts to begin the OS/emulation develompent. Maybe I can get some help from Erik Smith for the NUT emulation?? ;)

Anyway, I haven't yet the prototype PCB, only the bare 100-pin SMD chip and some ideas...

I accept any help that the comunity can give!

Best regards,

Nelson

P.S. About the internal pictures I promissed you - I was without internet on my home on the weekend, I'll manage to sent to you tonight.

I'll be bringing up the topic over at the OpenRPN boards soon. Chances are we will do a similar approach only using an ARM7 CPU, a flash chip, and perhaps our new *fix programming language.

I agree with Nelson that it would be crazy to modify the machine using anything beyond a header board. If you want a ton of extra features OpenRPN will probably be your best bet. I will talk to my cohort, Chad, about all this... We're working on a method to achieve triple molded keys at relatively low cost.