HP Classic Series Display Driver

[Harald]

I am really impressed by what Bernhard (Panamatik) and Tony(teenix) have done.
I especially liked that it is possible to transform a wookstock calculator into any modle you like with Bernhards newACT. And I thought it would be nice to have a similar solution for the classics, but Tony's hardware and software (teenix.org) can't drive the original display drivers.
So I started a little project myself and go some results. Here is a little teaser:



Tony has been really helpfull providing a software for the PIC that scans a 5x8 rather then his usual 6x6 keyboard layout. Now once we get the display data sent from his controller to my controller, all I need to do is design a PCB and we have a drop in replacement board for the classic series main boards.

But don't hold your breath, there is still some work to do...

Cheers,
Harald

[PANAMATIK]

Hi Harald,
How did you manipulate the classic display driver to show alphanumeric characters? You would be able to emulate much more calculators than I could do with the woodstock display hardware.

Bernhard

[Harald]

(09-03-2016 09:57 PM)PANAMATIK Wrote:  Hi Harald,
How did you manipulate the classic display driver to show alphanumeric characters? You would be able to emulate much more calculators than I could do with the woodstock display hardware.

Bernhard

Hi Bernhard,

The classic display drivers can display any combination of segments you like. The only exception is the decimal point:
- The decimal point always takes up a whole digit. It can't be combined with other segments
- The left most digit can't display a decimal point
- Two consecutive decimal points are not possible

This is to do with how the display drivers work. The cathode driver is a shift register that gets clocked by the anode driver. The anode drive decodes 5 data lines. There are 4 data words per digit on those 5 display lines. So in total there are 60 data words for the 15 digits. Every 4 data words the anode driver issues a step signal which clocks the cathode driver. But if the anode driver receives a decimal point it issues an extra step signal before the decimal point is displayed. Which means every decimal point reduces the the data length by 4 words.
After the last digit has been written a 1 needs to be clocked into the cathode drivers shift register.
You also have to be careful to only issue consistent data to the display driver. Otherwise it gets damaged. The problem is, that the anode driver must not charge any of the inductors if none of the cathode transistors are turned on. Because that would mean the inductors can't be discharged through the LEDs. That results in a high voltage on the driver transistors and they get destroyed.

How does the woodstock display driver work in comparison? I assume it has a fixed character set? How is that transmitted to the driver?

Which other calculators do you have in mind for emulation? Currently I am planning to just output display data received from Tony's PIC controller. I have the feeling writing an emulator is way over my head..

Cheers,
Harald

[PANAMATIK]

(09-05-2016 09:45 AM)Harald Wrote:  The classic display drivers can display any combination of segments you like. The only exception is the decimal point.

How does the woodstock display driver work in comparison? I assume it has a fixed character set? How is that transmitted to the driver?

Which other calculators do you have in mind for emulation? Currently I am planning to just output display data received from Tony's PIC controller. I have the feeling writing an emulator is way over my head..

The Classic display driver works obviously rather complicated. The Woodstock is made already much simpler. It receives an 8-bit serial code per digit from the ACT during the 56-bit data/instruction cycle, where only 4-bit are used for 15 characters plus space, and 1-bit for an additional decimal point. After 12 digits a display reset signal is issued to reset the shift register. The character set is very limited therefore and contains only the ten digits 0-9 and five alpha characters, usually E r o F P, to display "Error" and "OF" for overflow, P is not used.

The next emulation I'm preparing for, is never emulated before. It will be a little surprise and needs some weeks, or only days if I'm lucky.

Writing an emulator for classic or woodstock nowadays is relatively easy after Eric Smith has made his "nonpareil" publicly available. But teenix has done it by his own. Hats off.

Cheers Bernhard

[Harald]

(09-05-2016 06:30 PM)PANAMATIK Wrote:  The Classic display driver works obviously rather complicated. The Woodstock is made already much simpler. It receives an 8-bit serial code per digit from the ACT during the 56-bit data/instruction cycle, where only 4-bit are used for 15 characters plus space, and 1-bit for an additional decimal point. After 12 digits a display reset signal is issued to reset the shift register. The character set is very limited therefore and contains only the ten digits 0-9 and five alpha characters, usually E r o F P, to display "Error" and "OF" for overflow, P is not used.

The next emulation I'm preparing for, is never emulated before. It will be a little surprise and needs some weeks, or only days if I'm lucky.

Writing an emulator for classic or woodstock nowadays is relatively easy after Eric Smith has made his "nonpareil" publicly available. But teenix has done it by his own. Hats off.

Cheers Bernhard

I tried alternating between two different outputs to display the few combinations that are not possible such as all decimal points. But the display became far less bright.
Now I think you are displaying a couple of characters that way. But I didn't notice any change on brightness.Any idea why this is not visible?

I'll be eagerly waiting for news on your website or here

Cheers,
Harald

[teenix]

(09-05-2016 06:30 PM)PANAMATIK Wrote:  Writing an emulator for classic or woodstock nowadays is relatively easy after Eric Smith has made his "nonpareil" publicly available. But teenix has done it by his own. Hats off.

Cheers Bernhard

I did have some help from some kind Forum members :-)

cheers

Tony

[Harald]

Has anyone seen socketed anode and cathode drivers in the classic series yet?

Since I am playing with the display drivers right now, I sourced a couple of spare parts and received this:



Never seen anything like that before. Has this left HP like that?

[teenix]

(09-18-2016 09:18 PM)Harald Wrote:  Has anyone seen socketed anode and cathode drivers in the classic series yet?

Since I am playing with the display drivers right now, I sourced a couple of spare parts and received this:



Never seen anything like that before. Has this left HP like that?

Might have been a repair job way back when, and gives it some easy repair insurance if the fault reappeared.

[Harald]

A little update on the progress. The first prototype boards are here:



Mechanically they fit quite well. I think the holes for the connectors to the keyboard PCB could be 1/10 of a mm smaller, but they work OK.

The large Microchip PIC on the left (yes, I could have used a smaller surface mount package, but decided against it) runs Tonys (teenix) emulation. IC3 is the eeprom to emulate the card reader for the HP65 and HP67. IC4 is an FTDI chip to connect the PIC to the PC via USB. It should be possible to cut a hole in the battery compartment and plug a cable in from inside the battery compartment.
Finally the square chip on the right is a renesas microcontroller running my software that reads the display data sent by Tonys PIC and outputs that to the original display drivers on the keyboard PCB.

Now the software needs more work. So far the HP35, 45 and 80 work.
Tony has already been very helpfull and has done a lot of work adapting his code to scan the original 8 rows by 5 coulums keyboard rather than the 6x6 setup he is using in his hardware emulator.
Some of the caluclator models don't run yet and I am not sure why. I struggle a bit to work my way through Tonys (impressive!!) PIC assembler code. I am sure there will be progress when Tonys time permits to work on this again.

Cheers,
Harald

[teenix]

Hardly any difference at all :-)

Awesome.

cheers

Tony

[Harald]

There is a difference here though:

[Hans-Peter]

Hi Harald

It seems to be a very interesting project, not just a display driver (more a calc driver:-).

I have a non working HP65. There are only two segments shining.
Is there a chance to give him a new life with that Project?
Where is now the powersupply on the new board?

Best regards
Hans-Peter
   

[Harald]

(11-10-2016 10:31 PM)Hans-Peter Wrote:  Hi Harald

It seems to be a very interesting project, not just a display driver (more a calc driver:-).

When I started this thread it was about the original display drivers. Now it has become about a cpu board replacement for the classic series calculators. I will probably start a new thread once the board is fully working.

(11-10-2016 10:31 PM)Hans-Peter Wrote:  I have a non working HP65. There are only two segments shining.
Is there a chance to give him a new life with that Project?

That depends on what the problem is. If there is a problem with the anode or cathode drivers, I don't have a replacement for those,
If it is the main PCB, theoretically I could make a replacement PCB for that. The HP65 has a smaller PCB than the 35, 45, 70 and 80. So this would be a new design. But it wouldn't be possible (at least I would not know how) to use the card reader.

(11-10-2016 10:31 PM)Hans-Peter Wrote:  Where is now the powersupply on the new board?

The power supply is the little 5 pin IC next to the connector and the capacitors around it. This generates the supply voltage for the display driver. The two controllers run directly off the battery.

(11-10-2016 10:31 PM)Hans-Peter Wrote:  Best regards
Hans-Peter

Best Regards,
Harald

[PANAMATIK]

Hi Harald,

"Make Classics great again".

A very nice and awesome project. Impressive! My congratulations.

It is a full repair kit for the classic models (not display drivers and card reader).

How can I order?

If you need some help for the HP-55 and 70 emulation, please ask.

I made a similar design for the woodstock models, which replaces the complete board, but still no prototype made. If I finally make it, it will consume only 20mA when display is on and nothing in sleep mode. It will have real Continuous Memory because it never will be powered down, and it can display alphanumeric like yours, and of course Infrared printing and GPS.

Bernhard

[Harald]

(11-14-2016 07:45 AM)PANAMATIK Wrote:  Hi Harald,

"Make Classics great again".

A very nice and awesome project. Impressive! My congratulations.

It is a full repair kit for the classic models (not display drivers and card reader).

How can I order?

If you need some help for the HP-55 and 70 emulation, please ask.

I made a similar design for the woodstock models, which replaces the complete board, but still no prototype made. If I finally make it, it will consume only 20mA when display is on and nothing in sleep mode. It will have real Continuous Memory because it never will be powered down, and it can display alphanumeric like yours, and of course Infrared printing and GPS.

Bernhard

Hi Bernhard,

most of the work was done by Tony. The PIC is running his code and he adapted it for the different keyboard layout and wrote the code to send the display data to my controller. I struggle a bit with the huge, but very impressive PIC assembler code he has written. I have done a bit of assembler programming on Atemels, but no where near to this level.

I was going to give a few prototypes to people who would like to play with them. I'll put you on the list

Harald