HP97 The journey begins

[Harald]

I have probably missed the answer to the following question.
Are these two separate PCBs clipped together with the original metal clips? Is there a spacer in-between the two PCBs?

[teenix]

Hi Harald,

Yes, they are clipped together in the image with the original clips. The circuit boards have the small locating slots machined into them. The clips are not actually required though, although the slight extra overall width may help in securing the board in place. The boards are separated by a dense foam sponge layer. The display has a dedicated socket.

cheers

Tony

[Mike T.]

(02-25-2023 09:39 AM)teenix Wrote:  The Spice is almost there (tongue in cheek) Way more work than I originally thought. The 34C is shown in the image but the module has selectable 31E, 32E 33C, 34C 37E and 38C.

That is just AWESOME !!

[teenix]

Hi all,

Here's a pic of the completed setup with the LiPo battery and USB charger board in place.

The original low battery indicator lights up ok and should come on when the LiPo is at about 25% of capacity.

Just have to run the software through its paces and make sure everything works.

I got a bug myself overnight so might be a bit longer :-(

cheers

Tony

[dmh]

Hi Tony,

Looks very nice!

A couple of questions:

- You mentioned the board clips, does this mean it only works/fits into the solderless versions of the Spice series?

- is anyone making overlays for the Spice series to aid in using the different models from the one keyboard (key labels will still be the same of course)?

(02-28-2023 12:02 AM)teenix Wrote:  Hi all,

Here's a pic of the completed setup with the LiPo battery and USB charger board in place.

The original low battery indicator lights up ok and should come on when the LiPo is at about 25% of capacity.

Just have to run the software through its paces and make sure everything works.

I got a bug myself overnight so might be a bit longer :-(

cheers

Tony

[teenix]

I don't have a soldered Spice model. I just assumed, for economics sake that the outer cases would be the same design. If so, the new setup should just lock in with the 6 plastic clips, 3 each side of the calculator.

I don't know about labelling, although a bit of web searching should find a manufacturer, or method of doing something that would work.

cheers

Tony

[Harald]

(02-28-2023 01:43 AM)teenix Wrote:  I don't have a soldered Spice model. I just assumed, for economics sake that the outer cases would be the same design. If so, the new setup should just lock in with the 6 plastic clips, 3 each side of the calculator.

I don't have a soldered spice either, but I think, since in this case it's is just a single PCB that is clipped into the shell, the clips will be shorter.
The soldered Spices probably are not as common as the solderless ones. I used to have one, but swapped it at since point. All the others I have are solderless.

Cheers,
Harald

Update: I found a picture of the calculator I used to have:
   
Looks like the single PCB and plastic frame have the same overall hight and this would also work fine.

[teenix]

Hi all,

Latest Spice board is constructed.

This one has display drivers on board so will give the processor an easy run instead of it trying to provide the LED drive which is outside the max current for the IO pins.

I haven't turned it on or programmed it yet - almost too scared in case it goes poof :-)

Fingers crossed.

Yesterday I also added another programmable function for the HP-34C model. It works on the emulator, so should do on the board as well. It will generate a random number in the range 0 to 0.9999999999 You can access this by pressing the key combination [g][0] which can also be used in programs. The random result is placed in the X register and pushes the stack up a level. So, if for example, you want a random number between 0 and 9, press [g][0], multiply by 10. and do an INT.

Edit: I forgot to mention a big thanks to Harald for helping to check over the circuit.

cheers

Tony

[teenix]

Hi all,

Thought I might mention I got some circuit boards to do HP-91 and HP-92 CPU replacements.

Some software is written but a bit to go yet.

If I find the quite large amount of free time required, I might even be able to add in the HP-95C, but this will require a different processor which is still not available.

cheers

Tony

[Harald]

(03-29-2023 03:15 AM)teenix Wrote:  I haven't turned it on or programmed it yet - almost too scared in case it goes poof :-)

Edit: I forgot to mention a big thanks to Harald for helping to check over the circuit.

cheers

Tony

Maybe you should wait and see if it goes poof or not before thanking me :-)

[teenix]

(03-29-2023 10:16 PM)Harald Wrote:  Maybe you should wait and see if it goes poof or not before thanking me :-)

I got some time and plugged in the dodgy Spice display with the exponent LED digits only held in place with the multiplex wiring and the segments lit up nice and bright.

It's like the movie "Never Ending Story", the keyboard is not being detected now, but I think I just need to check the voltage levels with the new display drivers and make sure then PIC can see them.

cheers

Tony

[teenix]

Hi all,

Here's a pic of the working Spice - 31E model selected. The blue glow is the battery charge LED with the calculator connected to a USB port. The new display/keyboard circuitry seems to be working ok and has a nice bright display. Thanks for the help :-)

I am going to fully charge the battery and test the low battery indicator. There might be a circuit tweak needed if it comes on too early.

The Continuous Memory circuit has had a few issues, but seems ok. Thanks to Harald for some help.

I thought I might list the features now

Supported models 31E, 32E, 33C, 34C, 37E and 38C

Plug and play - no soldering required
New membrane keypad assembly
BT connectivity
LiPo battery powered
Internal USB battery charger, runs calculator as well
Continuous Memory storage - requires no battery power - new circuit saves an IC too :-)
HP34C has random number generator - can be used in programs
Decimal/Binary/Hex/Octal convertor
Storage for 300 programs each for 33C 34C and 38C
Text editor for creating names for stored programs
Option for display program text instead of numbers
Battery backed real time clock with alarm, +/- 5 PPM
Separate count up and count down timers with alarm
Selectable DDMMYYYY or MMDDYYYY date format
Printer interface to PC, same font as Topcat printers
Menu activated right switch (in case user's model does not have one)
Selectable key debounce
Menu selectable US or Euro mode
Beeper - selectable OFF/ON Loud/Soft
Menu selectable sleep function
Power on model display
Temperature display
PC interface - transfer options and programs - compatible with Teenix Spice emulator
Reprogrammable through serial port or external programmer

cheers

Tony

[dmh]

Wow!!!

Excellent work Tony!

When can we order and how much?

What is the best donor calculator or it doesn't matter?

[Steve Simpkin]

Tony, that is beyond awesome! This solution replaces so much of the original hardware that it almost seems like if we could get a new housing and keys made for a reasonable price, you could have a brand new HP calculator.

[teenix]

(04-21-2023 02:50 AM)dmh Wrote:  Wow!!!

Excellent work Tony!

When can we order and how much?

What is the best donor calculator or it doesn't matter?

Thanks, not too much longer I hope, just have to run a full test. Some bug will be there, and then write up the user manual.

Not sure on price yet, have to add everything up, but same deal as the others, not so much for profit. Just enough to keep the web site and development going.

Doesn't matter. If the module is used with a 31E calculator, there is a menu option to replicate the right switch in software, if say, you wanted to use it as a 34C. I won't have keyboard overlays though.

I forgot to mention there is also a menu option for a display dimming feature. This will dim the display to half normal brightness. Apart from using it in low light, with less average drive current, it may be useful to prolong the LED displays a bit longer.

cheers

Tony

[dmh]

I'm not far away if you want someone to do some testing ;-)

Will see what I have I could use...

(04-21-2023 04:23 AM)teenix Wrote:  Thanks, not too much longer I hope, just have to run a full test. Some bug will be there, and then write up the user manual.

Not sure on price yet, have to add everything up, but same deal as the others, not so much for profit. Just enough to keep the web site and development going.

Doesn't matter. If the module is used with a 31E calculator, there is a menu option to replicate the right switch in software, if say, you wanted to use it as a 34C. I won't have keyboard overlays though.

I forgot to mention there is also a menu option for a display dimming feature. This will dim the display to half normal brightness. Apart from using it in low light, with less average drive current, it may be useful to prolong the LED displays a bit longer.

cheers

Tony

[Massimo Gnerucci]

Well done Tony, as usual.
Can't wait to add at least one to your other boards.

[teenix]

Hi all,

I've been playing around with the low battery detect all morning. It has been a bit of a challenge to get the low battery LED to come on when required with the LiPo battery. It has a different voltage vs discharge curve than the old NiCads.

The Spice low battery LED basically has three states - off, partially on, and fully on.

When the LiPo gets near the low battery state, there are only 10's of millivolts change so it is a bit difficult to work with the original circuit. The change in low batt LED indication from partial to fully on is also a few 10's of millivolts. Anyway, I have it about as close as I can get.

I have been writing the user manual, and going over the software as I was writing it to make sure everything works ok. The calculator had a half charged battery and I have had the calculator on and off for the last 4 days. It is still working ok, so a fully charged battery should last for a good amount of time. I connected a 100 ohm resistor across the battery to speed up the discharge and the calculator should work right down to the last bit of charge left in the battery, although I was under the impression that LiPo's should not be completely flattened. The low battery LED should begin to light around the 20-30% remaining charge point.

I have the battery charging via the USB port, so I'll see how that goes. The calculator is still usable during charge.

cheers

Tony

[mfleming]

Modern batteries don't really fit the old voltage decline under load as cell discharges model. A voltage trip point would be pretty fiddly, and it might occur without informing the person if you're drawing current when off to maintain state.

Probably too late in the design for this suggestion but you could calculate the amount of energy consumed versus battery capacity, then use appropriate setpoints for warning vs. charge now annunciation. Normally you'd measure voltage drop across a low series resistor, but a simple formula could be a static discharge constant plus sum of lit segments. Not particularly accurate without a bit of tuning and tweaking, but good enough as a "horseshoes and hand grenades" level approximation. And it would be repeatable, inspiring confidence.

Perhaps use a low priority heartbeat interrupt handler to calculate and accumulate, reset when battery under charge?

[teenix]

I had thought of that. Seeing it is a software mod, perhaps at a later date. The battery LED will probably light at a low level sometime before the battery is discharged enough to be warrant recharging, but when the HP circuit trips the LED to the high brightness level it would be something to consider.