HP-97 enhancements

[Kees Bouw]

Some time ago, the magnificent Katie Wasserman found a way to enhance the functionality of a standard HP-97 by adding a Parallax SX28 microcontroller and a DS1302 clock. All this is described in detail in an article that can be found at https://www.hpmuseum.org/cgi-sys/cgiwrap...i?read=937. At the end a remark is added: "Etienne Victoria was successful in building this project and installing it in an HP-97 with the old style main circuit board." There is a link to pictures of Etienne's project but this link does not seem to work anymore.
Anyhow, Katie's project dates from 2009 and Etiennes from 2010 and in the meantime many new microcontrollers have appeared. Is there anyone who has enhanced the HP-97 with newer technology and would like to share this? I am thinking of hooking the HP-97 up to an Arduino somehow. One thing I would like to achieve is being able to show the complete stack (x, y, z, t) in real time on a display connected to the Arduino. Another is to be able to load and save programs from, for example, a USB stick. All thoughts and ideas are very welcome!

[teenix]

You never know, but I don't think the registers are directly accessible from any serial bus.

The clock project simulated key presses by placing values onto the PIK chip key data input lines at the right time and through the calculators normal key processing routines the value which ends up in the C register, was displayed.

I think the only time data is available is when the C register is being read or written to RAM. To extract this would require careful examination of the ROM instruction flow.

cheers

Tony

[Kees Bouw]

Just a few thoughts / questions.

The HP-97 has a "print stack" function, could this be used or modified so the output would be useable on the outside instead of it being printed?

Would it be possible to change or expand the rom code with extra functions?

Is there any equipment known that you could connect to the 50 pin connector of a HP-97S? Or did you have to create your own? And what about the software for it?

[teenix]

(02-18-2020 10:42 PM)Kees Bouw Wrote:  Just a few thoughts / questions.

The HP-97 has a "print stack" function, could this be used or modified so the output would be useable on the outside instead of it being printed?

Would it be possible to change or expand the rom code with extra functions?

Is there any equipment known that you could connect to the 50 pin connector of a HP-97S? Or did you have to create your own? And what about the software for it?

Same problem, the data paths for the stack registers are internal to the ARC chip.

Anything is possible. I am looking into a replacement CPU board for the 97 but still lots to do. It is more complex than the others I have done.

I did create a small circuit board, intending to make a 97 interface circuit, but I did not see the point. I may make something similar available if I finish the CPU replacement.

The driver software has to come out of your own grey matter. I think age is starting to get the better of me and mine is slowly morphing into don't matter :-)

cheers

Tony

[Kees Bouw]

(02-19-2020 12:01 AM)teenix Wrote:  Anything is possible. I am looking into a replacement CPU board for the 97 but still lots to do. It is more complex than the others I have done.
Tony

Hi Tony,

The HP-97 is like a small computer with a cpu, rom and ram, right? Which chip exactly is equivalent to the cpu? Is there a list or description of the instruction set? I have programmed in 6502 assembler long ago, is it anything like that? Is there a rom listing of the HP-97 anywhere (preferably commented)?

Thanks,

Kees.

[teenix]

(02-28-2020 12:01 AM)Kees Bouw Wrote:  

(02-19-2020 12:01 AM)teenix Wrote:  Anything is possible. I am looking into a replacement CPU board for the 97 but still lots to do. It is more complex than the others I have done.
Tony

Hi Tony,

The HP-97 is like a small computer with a cpu, rom and ram, right? Which chip exactly is equivalent to the cpu? Is there a list or description of the instruction set? I have programmed in 6502 assembler long ago, is it anything like that? Is there a rom listing of the HP-97 anywhere (preferably commented)?

Thanks,

Kees.

Hi Kees,

There is an instruction decoder in the ARC chip along with the registers, timing, access etc. The coding style is similar to other cpu's but more specific to calculator operation, although I guess you could get it to do other tasks.

Check out my HP-97 emulator. It should give you an idea of its source code and operation. You can also write your own source code as it has a compiler as well.

http://www.teenix.org

cheers

Tony

[Paul Dale]

The HP calculator processors are unlike the 6502.
It's still assembly code but the instruction set is quite different.

Pauli