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Woodstock Low Power
07-25-2017, 11:54 PM (This post was last modified: 07-26-2017 12:28 AM by PANAMATIK.)
Post: #1
Woodstock Low Power
A Low Power circuit for all "Woodstock" calculators!

This printed circuit board will become a complete replacement for the woodstock calculator electronics. It includes the ACT (Arithmetic Control Timing chip) and display driver functionality. Thus it will replace all chips of the original Woodstock PCB including the switching power supply and make a modern version of these LED calculators. It will consume remarkable 5-18 mA when switched ON, compared to 110-180 mA of the original calculator. And when switched off it consumes only 100 uA and keeps all data like an LCD calculator for years. The calculator will wake up by key press or by the ON/OFF switch.

The firmware contains all features of the new ACT chip, described in the ACTManual.

Furthermore it contains an accurate Real Time Clock with date, time, stopwatch and alarm time capability, including a Buzzer.

Flash ROM size is 512kB!!! This is enough to keep all ROM images of all Classic, Woodstock and Spice calculators including the HP-67 in one hardware, you can switch between all calculator models just by key press. And there is plenty of space for your programs.

It has full 7-segment alphanumeric capabilities and can show your program steps in plain text. Also the programs of your program library can be given names.

A GPS module can be connected and Infrared Printing to the HP82240B is available.

[Image: uc?export=view&id=0Bwx8KUfOUL_RZ3VwVklGYkQ0Ums]

The layout is nearly finished, as you can see in the above image. It will be inserted below the LED display board and drives its digits and segments directly. It takes the space of the original display driver chips. I hope to get the prototype boards in two weeks.

Price will be 149,- Euro + shipping, including Infrared printing, without GPS module.

Bernhard

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07-26-2017, 02:16 AM
Post: #2
RE: Woodstock Low Power
Will it support the 67's mag card reader?

Tom L

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07-26-2017, 04:00 AM (This post was last modified: 07-26-2017 04:01 AM by BobVA.)
Post: #3
RE: Woodstock Low Power
FANTASTIC! (And congratulations on this excellent work!)

I've got a million questions, but for starters:

- It sounds like the installation is designed for a Woodstock logic board with all the IC's removed, yes? Is it necessary / advisable to remove the power supply components as well?

- Does it make any difference what Woodstock logic board is used as a host?

- Will it use the same GPS module? Given the component removal, can it be installed facing up (assuming that will make a reception difference...not really sure if looking "through" the keyboard will be a help or a hindrance in that regard)

- Where does the new low power module fit? On the section of the logic board now holding the ACT? or on the display end of the board?

- Is there enough code space / IO / processor power to allow for a 1 PPS triggered/synchronized GPS time display? (The current GPS display appears limited by the accuracy of the NMEA stream and subsequent processing.)

- Can the GPS time set the RTC?

- Any possibility for an externally accessible interconnect to load/save programs or updates? (Perhaps replacing the existing - and presumably now completely vestigial - charger pins with a recessed micro connector or something?)

Very nice!!! Thanks for all your work on these old gems!

Bob

PS And, of course, what printing mode will be used for the TRACE function :-)
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07-26-2017, 06:40 AM
Post: #4
RE: Woodstock Low Power
(07-26-2017 02:16 AM)toml_12953 Wrote:  Will it support the 67's mag card reader?

This board does not fit into the HP-67 calculator. It only can emulate the HP-67 in a Woodstock calculator. For repairing or upgrading a real HP-67 you need the new ACT, which however doesn't handle the card reader.

But a similar board, adapted for the HP-67 with its 15-digit LED display and different layout is thinkable. It would replace the HP-67 processor board. But the display drivers are located on the keyboard. I'm not sure how difficult it would be to achieve a low power version without desoldering them. Perhaps then I should try to implement the card reader.

Bernhard

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07-26-2017, 07:24 AM
Post: #5
RE: Woodstock Low Power
(07-26-2017 04:00 AM)BobVA Wrote:  FANTASTIC! (And congratulations on this excellent work!)

Thanks for these million questions.

Quote:- It sounds like the installation is designed for a Woodstock logic board with all the IC's removed, yes? Is it necessary / advisable to remove the power supply components as well?

You have to remove only the two display driver chips. All other components, ACT, RAM, ROM and power supply components can be left in place. You have to cut just one copper trace to get the power supply disconnected. And you have to solder 7 wires from the new circuit to the keyboard pins.

Quote: - Does it make any difference what Woodstock logic board is used as a host?

No, all of them are suitable. Perhaps the location where to cut the power line and where to solder the wires are slightly different.

Quote: - Will it use the same GPS module? Given the component removal, can it be installed facing up (assuming that will make a reception difference...not really sure if looking "through" the keyboard will be a help or a hindrance in that regard)

Yes, it will use the same GPS module. If you remove the ACT chip you can locate it face up or face down at its place. Whether it makes a reception difference is still unknown. The keyboard does not shield measurable. But it could get better, because the noisy switching power supply is not longer there. I didn't yet test it.

Quote: - Where does the new low power module fit? On the section of the logic board now holding the ACT? or on the display end of the board?

It will fit at the display end of the board. The original HP board may not be removed. The pins of the new circuit are located exactly over the corresponding pins of the removed display driver chips and will be inserted into a low profile socket there.

Quote: - Is there enough code space / IO / processor power to allow for a 1 PPS triggered/synchronized GPS time display? (The current GPS display appears limited by the accuracy of the NMEA stream and subsequent processing.)

The GPS module sends the time every second and it will be displayed immediately after receiving the time string within 8 ms or so, one 12-digit display cycle is 3,5 ms. But I have no knowledge how accurate the time of sending the time string corresponds to the UTC second.

Quote: - Can the GPS time set the RTC?

Good question! Sure, I will provide a key sequence for it.

Quote: - Any possibility for an externally accessible interconnect to load/save programs or updates? (Perhaps replacing the existing - and presumably now completely vestigial - charger pins with a recessed micro connector or something?)

Yes, the 5-pin update connector on the upper left can be connected to an USB/TTL serial converter, where you can also upload and download your programs and you can remotely operate the calculator from the PC side!

Quote:PS And, of course, what printing mode will be used for the TRACE function :-)

MAN, NORM and TRACE mode selectable !!!!

Quote:Very nice!!! Thanks for all your work on these old gems!

Thanks!

Bernhard

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07-26-2017, 11:33 AM
Post: #6
RE: Woodstock Low Power
(07-26-2017 06:40 AM)PANAMATIK Wrote:  Perhaps then I should try to implement the card reader.

A micro SD card ought to fit into the card slot in the case and would make for a nice substitute for a magnetic card reader.


Pauli
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07-26-2017, 12:02 PM (This post was last modified: 07-26-2017 12:03 PM by PANAMATIK.)
Post: #7
RE: Woodstock Low Power
(07-26-2017 11:33 AM)Paul Dale Wrote:  
(07-26-2017 06:40 AM)PANAMATIK Wrote:  Perhaps then I should try to implement the card reader.

A micro SD card ought to fit into the card slot in the case and would make for a nice substitute for a magnetic card reader.


Pauli

Reading/writing SD cards needs an operating system or would consume lots of program space to implement the file system. Therefore I use the built in flash memory. An HP-67 magnetic card stores about 240 bytes, thus the 512k flash memory can store more than 2000 cards. And with loading programs into flash from PC it is virtually unlimited. No need for cards.

Bernhard

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07-26-2017, 02:01 PM
Post: #8
RE: Woodstock Low Power
Layout has undergone latest changes today and finally the prototype boards are ordered.

[Image: uc?export=view&id=0Bwx8KUfOUL_RWVdmVEZYc2kwODA]

This is a preview of the bare board, top and bottom view.
The gap in the board is made for the display holder/charger component.

Bernhard

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07-26-2017, 04:57 PM
Post: #9
RE: Woodstock Low Power
Wonderful!

What do you suggest for the power supply? Will two AA cells (ideally NiMH as I have plenty of those left from our son's toys which he has long outgrown) in the original battery holder be sufficient?

Regards
Max
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07-26-2017, 05:14 PM
Post: #10
RE: Woodstock Low Power
In thanks for your answers, here's another question :-)

- Will the LP board work OK if all the IC's on the logic board are removed? How about the rest of the components (power supply, passives, etc.)?

Quote:MAN, NORM and TRACE mode selectable !!!!

I'm completely sold now! :-)
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07-26-2017, 05:46 PM (This post was last modified: 07-26-2017 05:47 PM by PANAMATIK.)
Post: #11
RE: Woodstock Low Power
(07-26-2017 04:57 PM)Maximilian Hohmann Wrote:  Wonderful!

What do you suggest for the power supply? Will two AA cells (ideally NiMH as I have plenty of those left from our son's toys which he has long outgrown) in the original battery holder be sufficient?

Regards
Max

Thanks for your question about the batteries.

The circuit is specified from 2.3V to 3.6V. Also lower voltages down to 2.0V are possible but flash write (storing your programs) probably wouldn't work with these low voltages. Remember the HP-25 indicated low Battery at <2.5V. Either 2xAA cells non rechargeable= 3.0-3.2V , or rechargable AA cells = 2.5-2.7V are suitable. I also tried my prototype with the external charger, which produces 3.3V and this will also work. If you are having lots of standby time, then so called precharged AA cells with low self discharge would be best.

The original battery holder is best for all of these.

If you are using non rechargeable AA cells you will have a slightly brighter LED display,because of the higher voltage. But as this is a Low Power version I would accept the normal display brightness and suggest to use rechargeables.

Bernhard

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07-26-2017, 05:52 PM
Post: #12
RE: Woodstock Low Power
(07-26-2017 05:14 PM)BobVA Wrote:  In thanks for your answers, here's another question :-)

- Will the LP board work OK if all the IC's on the logic board are removed? How about the rest of the components (power supply, passives, etc.)?

Yes, you can remove everything if you want.

But please leave the connector prongs and the LED display, and the big resistor and diode if you want to use internal charging of batteries.

Bernhard

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07-28-2017, 05:51 PM
Post: #13
RE: Woodstock Low Power
HP-25 Emulator and real HP-25 calculator can communicate!

Today I connected my HP-25 PC Emulator application with my HP-25E ACT calculator via USB/serial converter. The intention was to test the interface between the PC and the coming HP-25 Low Power. Because the latter is not yet there, I used an HP-25E. I added a serial interface to the HP-25 emulator application and the corresponding interface into the HP-25E firmware.

Now when the converter is attached and you click one of the PC emulator buttons the real calculator gets the key code and calculates! It is like pressing the original keys, also when you hold down the SST key it behaves like holding down the SST on the real calculator until released. Also when you press a real calculator button, the LED display contents will be shown on your PC.

This is not the main goal I wanted to achieve, but a nice addendum. Mainly the interface will be used to upload/download programs and data (yes, in both directions) between the PC and the huge 512k flash memory of the HP-25 LP circuit. I programmed these routines already, but cannot test them until I get the first prototypes next week.

The PC HP-25 emulator program will be updated to contain all Classic/Woodstock/Spice calculators in one application. If you switch from one calculator to another on the real calculator, automatically there will appear this calculator on your PC.

I got a slight headache to solve a problem when writing a single HP-25 program into the flash area, while keeping the other programs as they are; a normal procedure. But not with a small PIC processor, because a complete 4kB flash area must be erased before you can write 49 bytes to it. The previous 4k contents has to be read first, then altered, and written back into the flash. But the PIC does have only an 80 byte RAM buffer! I solved the problem.

If all goes well, the HP-25 LP will become a unique calculator.

Bernhard

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07-28-2017, 10:03 PM
Post: #14
RE: Woodstock Low Power
Bernhard,

Are you "The Doctor"? I am just noticing that these Woodstock calculators are becoming much bigger on the inside than they are on the outside. :-)

Regards,

Everett
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07-29-2017, 06:12 AM
Post: #15
RE: Woodstock Low Power
(07-28-2017 10:03 PM)everettr Wrote:  Bernhard,

Are you "The Doctor"? I am just noticing that these Woodstock calculators are becoming much bigger on the inside than they are on the outside. :-)

Regards,

Everett

If you ENTER the calculator, there is a special key for it, this could be true.

Regards
Bernhard

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08-15-2017, 06:44 AM
Post: #16
RE: Woodstock Low Power
I received the Woodstock Low Power prototype boards last week. And spent some days to finish the software, which is not yet done. And will need more time, which I don't have at the moment. I hope all of you, which have interest in the HP-25/29 Low Power are in summer vacation anyway.

But everything is on track. The board is already running with display and keyboard functioning, battery voltage display, Real Time Clock running, and only minor layout issues are discovered. I hope to get all things done until mid of september. Thanks for waiting.

My fully functioning Pre Prototype HP-25 LP has become my only daily calculator. It makes so much difference if you don't have to switch off the calculator. Smile

Bernhard

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08-15-2017, 07:01 AM
Post: #17
RE: Woodstock Low Power
(08-15-2017 06:44 AM)PANAMATIK Wrote:  It makes so much difference if you don't have to switch off the calculator. Smile

I can appreciate this. My HP 45 at work is starting to have on/off switch problems.


Pauli
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08-15-2017, 03:03 PM
Post: #18
RE: Woodstock Low Power
(08-15-2017 06:44 AM)PANAMATIK Wrote:  I received the Woodstock Low Power prototype boards last week. And spent some days to finish the software, which is not yet done. And will need more time, which I don't have at the moment. I hope all of you, which have interest in the HP-25/29 Low Power are in summer vacation anyway.

But everything is on track. The board is already running with display and keyboard functioning, battery voltage display, Real Time Clock running, and only minor layout issues are discovered. I hope to get all things done until mid of september. Thanks for waiting.

My fully functioning Pre Prototype HP-25 LP has become my only daily calculator. It makes so much difference if you don't have to switch off the calculator. Smile

Bernhard

I'd be willing to sign up for pre-release, beta testing. And, if received in time, could take it to HHC 2017 in Nashville.
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08-15-2017, 08:11 PM
Post: #19
RE: Woodstock Low Power
I would appreciate that, but don't know whether I will be ready in time for sending a Woodstock Low Power unit to you before the HHC. But there is a friend here in germany who will join the HHC. I will ask him to carry a HP-25 LP to you and I will send you a manual in advance, hoping you will have some time to make a presentation.

Bernhard

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10-15-2017, 07:52 PM
Post: #20
RE: Woodstock Low Power
After Jim Johnson has shown the pre prototype of the "Woodstock Low Power" at the HHCH 2017 - thanks Jim for having made this presentation - there seemed not much news about the Low Power circuit.

I had to struggle with unexpected difficulties. But now the "Woodstock Low Power" circuit made more progress in the last week, than in many weeks before. The reason for the long delay was a layout problem with the first prototype PBC some weeks ago, which I couldn't resolve, whatever I tried. I couldn't get the processor running stable and spent a lot of time with it. Then I threw the PCBs away and made another layout and ordered more PCBs, which arrived last week.

This time I got the processor running as expected and very relieved I could work on the software. Meanwhile all components are working, including the RTC and the serial Flash memory. And the display is more bright than before because I added another driver chip. Today for the first time, I could switch via keyboard between several calculators. For programming of the 512k flash chip I had to write PC <-> ACT communication software for downloading the flash images containing all calculator ROM codes and keyboard code tables, and print and display mnemonics and and and..... There will be about 20 calculators integrated in the final version. For now only the Woodstock and Spice Models are working, but the Classics will follow soon. There is plenty of space for thousands of RPN programs in the flash memory. The GPS module will be tested in the next days.

Until now all promised specifications of the "Low Power" will be met. I'll keep you informed about the next steps and further progress.

P.S. No photos of the prototype this time, because I gave my camera to my son for traveling in australia, will get it back not before next summer. Sad

Bernhard

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