HP97 The journey begins

[teenix]

Hi all,

After playing around with the PGM/RAM banking it is a bit clutzy to use.

The functioning of this is quite complex as my software has to interact with the original HP code and make minor changes to the data as the HP code does its normal processing. Even though it "appears" to work, the HP code is written in a way that preserves the precious ROM space and some code parts are shared with different routines. Some code also jumps into mid points to subroutines as well. This means that tracing the code as it operates can be tricky and as my code relies on things happening in certain sequences, something may happen that only appears that the sequence was working as expected.

Anyway, the long and short of it is that this will take some time to get going properly without modifying the HP code which I don't want to do. There are lots of other modifications required for the memory storage and PC software to cater for the different program/RAM sizes as well.

This will happen eventually, but for now the HP-97 seems to be functional although I'm sure some bug will surface when someone else uses it. I get too close sometimes and can't see the weather through the weather. The boards can be re-flashed so new software shouldn't be a problem.

I have written the 97 code in such a way that re-flashing can take as little as a second depending on what the uploader has to do. This should help to minimize re-flash errors. To help protect the print heads if re-flashing fails and the software goes crazy, the chip will revert to a special boot mode in protected code space, and the only thing it can do is wait for another re-flash.

Some extras that were added are battery-less Continuous Memory, Message printing, time/date printing, battery backed clock with alarm, 97S mode, text displayed program key codes, program storage for over 800 cards, Bluetooth and USB connectivity, re-flash via USB, quick disconnect printer ribbon, original battery charger and protection circuit, and HP 82240 IR interface. Installation is direct plug in replacement, however, the two wires for the charge socket need to be unsoldered and then soldered to the new board. If external charging is preferred, then this can be omitted. You could also discard the battery and run an external 5V 3A plug pak to power the unit if required. All other wiring for the printer and paper advance switch are connected from the top of the board and are easy to plug in.

I have a few PIC chips, other parts and circuit boards available to build just a few boards.

If anyone wants one then please PM or email me. I'll leave them for a day or so, and if I there are more queries than I have parts available for, I will "spin the bottle" at the names and the first that pop out can have first go with the ones that I have.
.
cheers

Tony