25th anniversary of 15C's introduction in 2007



#2

Happy New Year for everyone! And maybe happier in 2007??? Who knows about any good news - will HP bring back 15C or not?!

Cs.


#3

Great idea! I would highly appreciate it!!!

#4

The limited resources of the HP calculators division favors the NOT alternaitve!!!

#5

Why not force a 25th anniversary edition? Given that nonpareil now supports voyager ROMs, it should be possible to gut a 12c, put in a new board (and perhaps better tactile domes), silkscreen on new labels and sell it. By 2007 OpenRPN will have the facilities to make a conversion kit. Perhaps the threat of unauthorized 15c's would be enough to get HP working on it?

I would propose an ultra low-power MCU, and no I/O. To make the PCB fit properly we can invest in a heat-stake press. If anyone wants to do it, I am willing to supply web space and manufacturing/design help.

Let me know if you want to take on a project like this.

regards,
Hugh


#6

Any of the MSP430F4xx would do quite easily:
builtin LCD driver for up to 160 segments, up to 60KBytes of in-system programmable flash, 2KBytes of ram, up to 48 bits of programmable i/o (for the keyboard scanner -- you don't even need a multiplexer). All you need is a case, buttons and a 32KHz oscillator...


#7

As has been mentioned many, many times before, the electronics is (relatively) easy. It is easier still to make grand plans that never appear all whilst making vague promises.

Sadly designing, building and producing the hardware on a large scale is quite hard. Unlike pure software project it requires many different skills - programmers, engineers (electrical and mechanical), technicians, industrial designers etc. Finding all these people and getting them to work for free is a challenge.

Then you have to consider the money involved. Even though the money required is very small compared to the value of time spent people are still reluctant to invest cash. Production tooling isn't cheap. Almost every single "open hardware" design involving production to date has failed.

Please note that I am not talking about 'IP cores' - designs written in hardware design languages like VHDL / Verilog. These skip the whole mass-production phase. Problems still exist with IP cores as seen here

#8

Quote:
Any of the MSP430F4xx would do quite easily: builtin LCD driver for up to 160 segments, up to 60KBytes of in-system programmable flash, 2KBytes of ram, up to 48 bits of programmable i/o (for the keyboard scanner -- you don't even need a multiplexer). All you need is a case, buttons and a 32KHz oscillator...

I've done several MSP projects, and yes, in principle it is quite easy, really! But, and this is a very important "But": it is one issue to write a hello world program with the provided compiler - there is even a gcc available - and download it via boundary scan pins to the chip - the real challenge then is the final system, the prototyping and the production.

The above is basically unrealistic blurb copied from the data sheet, unfortunately: You almost never run the MSP with a single 32kHz quartz - for calculator purposes this is way too slow; you'll have to add a second one, and then lose those uA power consumption - the MSP will need more current. The 32kHz are realistic for power-down mode mainly.

Also: you either have 160 segments LCD (multiplexed!) or 48 I/O pins, so you'll have to carefully check what display you hook and how you merge it with the keybord scanner. Of course there are also some interdependences between the available pins and features like I2C bus, RS-232, A/D-D/A converters - if you start just straight forward, you'll find yourself blocked eventually with competing requirements - choose among 3 of the 7 requirements that you need; the chip can do all 7 things but only 3 at a time (typical effect).

The MSP chip itself is not easy to handle for a hobbyist, you better look at the TSSOP SMD package in the datasheet to check that you can solder this beast (you can - I learnt it, but if you are accustomed to DIL and std SMD SO packages, the pin distance is a challenge. There are of course adapters and prototype boards from Olimex and Elektronikladen.de, resp., but they are not useful for the product.

The LCD brings up a different question: the HP calcs have numerous special annunciators on their displays (low bat, flags, DEG/RAD mode, function keys) etc. As a hobbyist, you have to use an available LCD; you cannot produce a custom one - too expensive for the experiment. Unfortunately, you either find standard alphanumeric ones, with an own controller and incredible current requirements - you cannot use the MSP's LCD driver feature, or you find just normal 3 1/2, 4 1/2 digit multimeter displays (designed for ICM721x multimeters, which are unusable). You can try to cannibalize an alphanumeric display and control it by the MSP to reduce chip count and current, but the display itself has similar pin distances as the MSP itself, so better find a good PCB layout program and a good PCB producer (Sure there are some - but you'll have to find out the good, the bad, and the ugly yourself).

Of course, besides well-considered system design, you have to program the chip as well. This is no longer MSP specific, but still important. For a calculator, you want to have correct mathematics, so don't just take some multiplication/division routine or some trig functions, etc. from some text book, but invest a minute or two (or some thousands) on optimized and accurate algorithms. This is commonly neglected in almost all hobbyist projects - it was hard to get it compile at all, in all the hacking nights, so "someone else" should add the missing 5% (which turn out to be another missing 95%).

But then, the MSP might be a viable solution for such a project. However, numerous other controllers are then as well - concentrating a project on some single chip which appears attractive is seldomly successful. One better does not start with the chip, but with the design.

Holger


#9

Holger,

Quote:
For a calculator, you want to have correct mathematics, so don't just take some multiplication/division routine or some trig functions, etc. from some text book, but invest a minute or two (or some thousands) on optimized and accurate algorithms. This is commonly neglected in almost all hobbyist projects

That sometimes goes badly wrong even at big companies. One of the first TI LCD calcs, the TI-25 can't calculate 7^8 correctly. It yields 5764800 (exact integer!) instead of 5764801. It looks like the calculation goes IP(8*10^LOG 7).

Marcus


P.S: Are you the XFree OS/2 guy working in Birlinghoven?


#10

Quote:
That sometimes goes badly wrong even at big companies. One of the first TI LCD calcs, the TI-25 can't calculate 7^8 correctly. It yields 5764800 (exact integer!) instead of 5764801. It looks like the calculation goes IP(8*10^LOG 7).

IIRC, the TIs were well-known for lousy math for long time. Known problems with TI-52, TI-56, TI-58/59 were reported 20 years ago in the German Funkschau magazine. But HPs, particularly also older ones - no need to talk about Kinpo crap - also have certain artifacts even with or probably particularly because of BCD arithmetics.

Quote:
P.S: Are you the XFree OS/2 guy working in Birlinghoven?

Yes.

#11

Quote:
You almost never run the MSP with a single 32kHz quartz - for calculator purposes this is way too slow

With a 32kHz external quartz, you get around 2MHz of MCLK: not a speed demon but still quite fast for the HP15C standards...

Quote:
you either have 160 segments LCD (multiplexed!) or 48 I/O pins, so you'll have to carefully check what display you hook and how you merge it with the keybord scanner.

With the full 160 segments you still have more than 30 gpio pins available, plus some input only or output only pins. With 16 pins you can control a very large matrix scanned keyboard. This if you don't plan to use an external binary decoder for the column scanner.

Quote:
The LCD brings up a different question: the HP calcs have numerous special annunciators on their displays (low bat, flags, DEG/RAD mode, function keys) etc.

We're talking about the hypotetical possibility of gutting an HP12 here, so the LCD is quite the easiest part...

Quote:
The MSP chip itself is not easy to handle for a hobbyist, you better look at the TSSOP SMD package in the datasheet to check that you can solder this beast

In fact even the smallest form factor may be TOO BIG for the intended use...


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