New (and compact) ZVC design.

[Diego Diaz]

Hi all,

During the last few weeks I've had email discussions with some well known contributors who consider that there is a real demand for such a device.

First, Christoph Klug and soon afterwards, Sylvain Cote and Robert Prosperi; agreed on that, despite my initial doubts about the idea.

I was wrong, and when three "heavy weights" of this small community share a common interest it's time to rethink your (my) position, and give deserved credit to them for bringing this up. :-)

After a while I had a New ZVC converter design on the drawing board (AKA: PCB design app) and the parts on their way.

Yesterday I finally got the first prototype ready. But no ZEPROM to test it with... :-(

Luckily enough, the design is so simple that it's almost impossible to get it wrong... well, I know, (Err... Murphy and all that.) and yes, the LED limiting resistor should be a bit higher. (It looks way brighter in the picture though,: but still too bright IMHO).

Pictures in the links below.
https://photos.app.goo.gl/qHhKWV33fhpeQ6e49

https://photos.app.goo.gl/TXkUSTrmWwGzfPbh8


From the technical side, it's just a DC/DC converter (the same type used in the 82120D Power Bank) configured to provide a 12v output, a switch to select RUN or PRG (PRoGram) mode and one LED to give visual feedback of the latter; all these onto a gold plated PCB of the same type as used on the PicKit2 programmer for the NoV's and Clonix modules, to improve contact reliability.

As usual, comments and questions are most welcome.

All the best from the Caribbean.

Diego.

[Sylvain Cote]

Hello Diego,

This is great news !!!

Do you need ZEPROM's for your testing? I have plenty.

This new device needs a name ...

DVC → Diego Voltage Converter ?
ZVC2 → Zeprom Voltage Converter version 2 ?

Some background ...

• The ZEPROM is a 16K EPROM module for the HP-41 that was made by Zengrange.
  
• The module can be configured as
  • a flat 8K module
  • a flat 16K module
  • a banked switched 12K (4K+2x4K) [this is a banked switched 16K with a special setup]
  • a banked switched 16K (2x8K)
    
• The PROGRAMMMER ROM is normally used with the ZVC to program the ZEPROM. (The ROM was burned in each ZEPROM sold)
  
  Code:
  

  XROM   FUNCTION  DESCRIPTION
-----  --------  ---------------------------------------------------
09,01  ADDBSW    Add bank-switching code to initialised page
09,02  ADDMCF    Add M-code bank-switching functions
09,03  ADDUCF    Add user code bank-switching functions
       BGTOxx    User code bank-switching GTO
09,04  BLANK?    Test if the page in Reg X is blank
09,05  BNKSW?    Test if page in Reg X is bank-switched
       BRTNxx    User code bank-switching RTN
09,06  BURNUC    Burn user code program from RAM or ROM
09,07  BURNWD    Burn word in Reg X into address in Reg Y
       BXEQxx    User code bank-switching XEQ
09,08  CHKSUM    Compute & return checksum for specified page
09,09  COMPUC    Compile user code program in mai nmemory
09,10  COPYPG    Copy entire 4K image between pages X & Y
09,11  CPXYZ     Copy data as specified in Regs X,Y,Z
09,12  DECHEX    Convert decimal value in Reg X into hexadecimal
09,13  ENABLEP   Enable primary bank of ROM page in Reg X
09,14  ENABLES   Enable secondary bank of ROM page in Reg X
09,15  FRSPC?    Address and amount of free space of page in Reg X
09,16  HEXDEC    Convert hexadecimal string into decimal number
09,25  ILBURN    Burn page using image from IL mass storage file
09,26  ILSAVE    Save ZEPROM page image into HP-IL mass storage file
09,17  INITPG    Initialise a ZEPROM Page
09,22  PB09      Enable primary bank of Programmer ROM module
       PBxx      Enable primary bank of ROM with XROM-id of xx
09,23  PGX=Y?    Compare two 4K ROM pages for equality
09,24  PRGMLN    Return program length and number of LBLs
09,25  READWD    Read word from ROM page in RegX
09,26  REBURN    Recover from error in burning user code program
09,27  RRBURN    Burn ZENROM ROMREG + format data into ZEPROM
09,28  SB09      Enable secondary bank of Programmer ROM module
       SBxx      Enable secondary bank of ROM with XROM-id of xx
• Zeprom Programmer's Manual
• A UV light box is needed to erase the module.
  
• A Zeprom Voltage Converter (ZVC) or the new module from Diego is needed to program the module.
  
  
  
  

There are lots of programmed ZEPROM modules floating around on eBay.
Until today, the ZVC rarity and the associated asking price prevented to reused those modules.
For sure, the ZEPROM is not as powerful as the Clonix-D module, but if they can be reused why wasting them.
Thank you Diego!

Oh! and BTW, I will take three units when available. ;-)

Best regards,

Sylvain

[PeterP]

Diego, what wonderful news!

I would love to sign up for a couple of them when they are available. Also, you mentioned it is a very simple design, will you releasing the schematics / gerber files potentially?

Thank you for keeping on innovating!

Cheers

Peter

[bxparks]

(05-19-2024 02:17 PM)Sylvain Cote Wrote:  

• Zeprom Programmer's Manual
• A UV light box is needed to erase the module.
• A Zeprom Voltage Converter (ZVC) or the new module from Diego is needed to program the module.
  

Thank you for providing this informative context for people like me who don't know the HP-41. (I've always wanted one, but could never afford one, and when I had the money, I had no need for a calculator).

So this ZEPROM requires a UV light to erase, which can be inconvenient if recall. An EEPROM (aka "flash memory") would be a lot easier.

Are there any HP-41 ROM modules that use a modern embedded microcontroller with built-in flash memory to emulate the HP-41 ROM module? I'm thinking along the lines of an ESP-8266 with 1-4 MB of QSPI flash memory. I think the cost for that combo is somewhere in the $1-3 range. I would expect the 80 MHz CPU could bitbang the HP-41 I/O interface in software. And the deep sleep power drain of the ESP8266 is in the range of 20 microAmps, which I would think is low enough for an HP-41 ROM module.

If the ESP-8266 isn't fast enough, there are many other cheap, powerful, and low-power ARM-based microcontrollers: the 48 MHz ATSAMD21 Cortex M0+, the 120 MHz ATSAMD51 Cortex M4, the RP2040 with its dual-core 133 MHz Cortex M0+, to name just a few.

(Apologies if I'm regurgitating a well-beaten topic... I don't follow the HP-41 world.)

[Didier Lachieze]

(05-19-2024 08:08 PM)bxparks Wrote:  Are there any HP-41 ROM modules that use a modern embedded microcontroller with built-in flash memory to emulate the HP-41 ROM module?

Yes, since 20 years with the Clonix and Nov modules from Diego Diaz and their PIC microcontrollers

(See The Clonix-41 module turned 10 for more details)

[bxparks]

(05-19-2024 08:29 PM)Didier Lachieze Wrote:  Yes, since 20 years with the Clonix and Nov modules from Diego Diaz and their PIC microcontrollers

(See The Clonix-41 module turned 10 for more details)

Ah got it. I saw a reference to that when skimming through the various references posted by @Sylvain Cote, but I did not realize what it was. Most of the product names related to HP-41 peripherals and software are opaque and non-self-descriptive to me.

[ThomasF]

(05-19-2024 08:08 PM)bxparks Wrote:  Are there any HP-41 ROM modules that use a modern embedded microcontroller with built-in flash memory to emulate the HP-41 ROM module?

Hi,

First, this is to help with existing (old) modules (and not as a new device for the 41).
And secondly yes, there are of course other alternatives!
Search for Clonix and you will find a PIC solution, or take a look at the work done with a RP2040 here.
There are several other topics as well regarding this path (with the Pico) on this forum, and there are some hardware designs coming up soon as well.
Both of these use more modern devices to extend the HP41 family.

Cheers,
Thomas

[Diego Diaz]

Hi Sylvain, Peter,

Thanks for your kind words. :-)

@Sylvain: I really appreciate your offer to send a ZEPROM for testing, however, I'm about to leave (back to the Canay Islands) in a couple of weeks, so chances are that it doesn't arrive on time.

Also, I don't have any previous experience programming ZEPROMs, hence I think I'd better send you one of the prototypes for you to evaluate whenever you have the time.

There's a small label at the back of the PCB: "ZVC Replica DD May 2024". Yep, not a great effort of imagination I'm afraid.

@Peter: As usual, the most difficult part is finding/purchasing modules to reuse the shells and (specially) the connector. More about that on a forthcoming thread.

I think in selling the populated board (tested) to those users who already have a spare module and the will/skills to solder the connector to the ZVC. This may go for about 40Eur including registered shipping as usual.

The assembled unit will be on the 80Eur mark. Again, registered shipping included.

Picture of the internals during assembly in the link below:
https://photos.app.goo.gl/Qb6TARLuqJ8bq8Kt5

These are quite likely to be on That Auctions Site you all know.

Still pending a few electrical test, mainly AC noise, since (contrary to the HP-41 itself) the ZEPROM module does not have much filtering at its input (if any).

Best wishes.

Diego.

[rprosperi]

This is indeed great news Diego, it will allow all those ZEPROM modules out there with Surveying applications to be readily repurposed into something actually worth using!

I wish I had known about this before I sent the recent pkg to you, I could have sent a ZVC for study and measuring, etc. but I nevertheless have confidence you'll get this right the first time, even without an original to study.

I will be buying 2 of these when ready. I thought about getting three units, but I want to preserve the option of calling Sylvain out for having more of any given 41 accessory than anyone else.

Looking forward to seeing these. Although the concept is not complex, and the process of burning is the very essence of simplicity, it is somehow also very satisfying using a 41 to burn it's own EPROM module. It just seems it shouldn't be this simple. but it is.

[Ángel Martin]

Diego, Just adding my voice to those already here - this is indeed a worthwhile and very welcome addition. The photo shows a clean and well-rounded design, please put me down for ONE assembled unit when possible. Thanks much!

Saludos,
ÁM

[Diego Diaz]

Hi Bob, Ángel, all,

Thanks for the positive welcoming you've given to this small new project.

@Bob:
I'd rather prefer sending you a prototype. First, you've done the ZEPROM programming previously; and second, the ZEPROM itself and the ZVC are far more valuable items and having them shipped back and forth may pose an unnecessary risk.

Will keep in touch.

Best.

Diego.

[Ángel Martin]

(05-21-2024 04:19 AM)Diego Diaz Wrote:  I'd rather prefer sending you a prototype. First, you've done the ZEPROM programming previously; and second, the ZEPROM itself and the ZVC are far more valuable items and having them shipped back and forth may pose an unnecessary risk.

If it helps the (sending) logistics, I also have available Zeproms (and in fact also the original ZVC from Zengrange) - so once you're in Canarias you can send me via domestic mail a prototype for testing... (of course I'm assuming there's more than one available, I'm not trying to snatch Bob's unit here)


Ángel

PS. To add to Sylvain's excellent recap on this subject - the Zeproms have a unique feature that still make them valuable to the intrepid user: they support bank-switched FOCAL programs, imagine...

[rprosperi]

(05-21-2024 06:59 AM)Ángel Martin Wrote:  If it helps the (sending) logistics, I also have available Zeproms (and in fact also the original ZVC from Zengrange) - so once you're in Canarias you can send me via domestic mail a prototype for testing... (of course I'm assuming there's more than one available, I'm not trying to snatch Bob's unit here)

@Diego - Please send units to Sylvain and Angel well before me. I have used the ZVC only 3-4 times, basically just enough to learn to use it, and then to restore some ZEPROM modules to their as-shipped condition with the "-PROGRAMMER" ROM, so I'm certain Angel and Sylvain can test your new device better than I can. I do simple, vanilla 'copy this ROM to EPROM' while they are doing complex tasks which will probably more quickly find issues, if indeed there are any.

[Diego Diaz]

Hi all,

Currently, I have three complete (with shell and contacts) prototypes built and another three barebones boards.

All of them have already been requested from the 'usual suspects' and will be shipped as my spare time allows. Some from Dom. Rep. and some from Spain.

Six more will be available once I'm back in the Canary Islands (and have overcome the nasty jet-lag)

Will be contacting you as parts and shipments become ready.

Best wishes.

Diego.