HP-71b - Future "SD-RAM" Module - viable ?

[JanS]

Hello Everyone,

you might have seen my earlier post about the newly aquired 71B. I really like the machine and I'm still at the beginning of the learning curve. While examining all it's different parts, I could not help but notice this coincidence in dimensions:

   
   
   

From a mechanical point of view, this seems doable, however, as I'm not an EE and have no real microcontroller programming expirience, this is something that I'll probably never achieve - but one can dream.

Maybe someone more familiar with the intricacies of building something like i.e. the FRAM module can voice their opinion with regard to viability of something like this.

Stay healthy and keep calculating,
Jan

[mfleming]

Interesting observation! The angle the SD card makes to the horizontal plane would make using a standard PCB mount SD card holder a challenge. Spring contacts would likely be needed. Logic level translation aside, how would the SD card appear to the 71B O/S? HP-IL disk drive? Feel free to speculate (or dream).

[KeithB]

I keep trying to decide whether it would be better to write code to get the 71 to access the card directly, or get a small MCU to translate between the 71 and the card using FatFS:
http://elm-chan.org/fsw/ff/00index_e.html

I lean towards the latter.

But it would have to get in line behind all my other half baked projects.

[JanS]

@mfleming:
The PCB inside the housing could pick up the angle determined by the slot - so using a standard "clicky" sd card holder should be possible. With regard to what the device should do, i think FRAM alike operations in addition to HP-IL device Emulation (if possible at the same time) for Disk Drive and possibly a printer like device that logged output to a text file.

@keithb
Definitely MCU based, so as to be able to pull itself into operation by just having the right files stored on the SD Card and having them presented to the 71b.
An ESP32 would probably fit into the enclosure space and add WIFI & BT to the mix. Thos could even be toggled by the 71 and stay off until needed. LEX files and I/O data could be shared via Wifi, somewhat similar to what your FatFS on a Flashair is doing.

Who knows - two such devices could probably do HP-IL over the airwaves.

Again, I'm not an EE, so I'm not sure about power consumption / startup times etc.

So, just a dream at the moment....

Stay Healthy and keep calculating,
Jan

[HP-Collection]

I dont think, the MicroSD Card has to be accessable from the side. It could be included in the cardreader housing.

[Jeff_Birt]

A friend of mine came up with this serial interfaced SD card 'drive' a while ago. Primarily he made it to emulate the Tandy Portable Disk Drive 2 for the Model 100, etc. We had a batch made up and then the chip shortage

He has since developed firmware to support the Epson HX-20 and PX-8. It also works with the Sinclair Z88 with a few TPDD-2 clients that were written for it back in the day. He just added XModem support so any RS232 device that supports file transfers with XModem would work as well. So 'if' you had the RS2332 interface for your HP-71 and XModem transfer program, but that sort of defeats the purpose.

He did bring power and the SPI lines out to the DB25 but all other signals are RS-232 levels. Is three TTL level lines enough to do HP-IL? Just thought I would bring it up as an idea of what is out there. I find the size of the device makes is convenient and it runs on a single AA battery.


Link is my website, for informational purposes. They are not available at this time anyhow.
TPDD-2 Backpack

[KeithB]

"Is three TTL level lines enough to do HP-IL?"

No.

http://www.hparchive.com/Journals/HPJ-1983-01.pdf

[Jeff_Birt]

I glanced quickly though the PDF, thanks for that. I was not meaning to imply 'only' three I/O pins and nothing else would be required.

Looking at page 14, Figure 7, Ignoring the components needed for the differential bits of the circuit to the right you have a Tx line and an Rx line. There are no other control lines used. Thus with the other parts added to create and decode the differential signal you 'could' use only 2 I/O lines.

[mfleming]

(09-06-2022 02:23 PM)JanS Wrote:  An ESP32 would probably fit into the enclosure space and add WIFI & BT to the mix. Thos could even be toggled by the 71 and stay off until needed. LEX files and I/O data could be shared via Wifi, somewhat similar to what your FatFS on a Flashair is doing.

Tony (teenix) has a similar arrangement with his Classic CPU board replacements. The boards have a Bluetooth transceiver that can be turned on and then linked via a COM port connection to a program to transfer data back and forth. For the 71B you'd probably want to emulate an HP-IL peripheral controller and interact with the pyilper program on a nearby computer.

~Mark

[Garth Wilson]

I, too, have kept hoping someone would introduce such a product; but instructions should be compatible with the HP-IL file-access instructions that are already in the HP-IL module, and I think it would have to be an HP-IL device. This goes for the 41 also, even though a MicroSD card would fit in a top-port module which mechanically would be a neater solution (assuming you have a port available).

I am not aware of any bluetooth transceivers that can interface to lots of things at once like HP-IL can.

[mfleming]

Think of the Bluetooth module as a wireless PIL-Box . . . driven by an emulated HP-IL interface.

[J-F Garnier]

(09-06-2022 08:39 PM)Garth Wilson Wrote:  I, too, have kept hoping someone would introduce such a product; but instructions should be compatible with the HP-IL file-access instructions that are already in the HP-IL module, and I think it would have to be an HP-IL device. This goes for the 41 also, even though a MicroSD card would fit in a top-port module which mechanically would be a neater solution (assuming you have a port available).

No, it doesn't need to be a HP-IL device, actually linking it to the HP-IL would be complicate, do you image two HP-IL cables coming from the HP-IL module to the SD card module, and then going outside to regular HP-IL devices? Well, the HP-IL ROM is able to manage 3 HP-IL loops, so it could be possible to emulate a separate HP-IL interface dedicated to the SD card. Still quite complicate.
An other possible approach would be to manage the SD card as a new device type for instance XMEM (like the 75C POD) or EDISC. The HP-71B system is designed in such a way that the HP-71B will poll the LEX files for a handler for unknown device types (this is how the HP-IL ROM extends the built-in command CAT, COPY , ...). So all you would have to do is to write a LEX file to manage your SD card, in the way you want.

(09-06-2022 09:35 PM)mfleming Wrote:  Think of the Bluetooth module as a wireless PIL-Box . . . driven by an emulated HP-IL interface.

Something like this: HP-IL Bluetooth PIL-Box ?

Let me also remind you the IL Drive (a HP-IL disc emulation using a SD card) built by Tobie several years ago based on the PIL-Box.

J-F

[Garth Wilson]

J-F Garnier, it has been so long since I last used the 71 that I had to review how it handles the files, and I am reminded that it does make it easier than the 41cx does to do file operations at different locations and specify the location. What I use every day is the 41cx whose file operation commands are one set for XMEM, another set for HPIL, and if there were a module with MicroSD, it would have to be yet another set.

However, I have two tape drives, which I've used for both the 41 and the 71, and if one had the conversion to accept SD card (it wouldn't have to be MicroSD), the same drive could be used for both machines. (Actually I have a 75 also, but it was given to me in very beat-up condition, with no manuals, and I've never used it except to verify that it does work. Further, I have two 71's.)

[mfleming]

(09-07-2022 07:15 AM)J-F Garnier Wrote:  An other possible approach would be to manage the SD card as a new device type for instance XMEM (like the 75C POD) or EDISC. The HP-71B system is designed in such a way that the HP-71B will poll the LEX files for a handler for unknown device types (this is how the HP-IL ROM extends the built-in command CAT, COPY , ...). So all you would have to do is to write a LEX file to manage your SD card, in the way you want.

So, if I understand you correctly, you start with creating a new device and hook its LEX handlers into existing commands (CAT, COPY, ...) and add new commands to reflect the device storage model. Commands like CD, PWD, MKDIR for a FAT-based storage model or MOUNT, UMOUNT if you want to keep a LIF disk model of storage. If hardware is implemented in the card reader slot the LEX code would manage hardware via the card reader device address.

BTW, with regard to the thread title, a microSD card or any flash device for that matter, would not be ideal for continuous use even as a ROM. Flash draws tens of mA current in use and so would be best for secondary storage.

(09-07-2022 07:15 AM)J-F Garnier Wrote:  Something like this: HP-IL Bluetooth PIL-Box ?

Let me also remind you the IL Drive (a HP-IL disc emulation using a SD card) built by Tobie several years ago based on the PIL-Box.

J-F

Thanks for the reminder! Forgot these, especially the second one

[Maximilian Hohmann]

Hello!

(09-07-2022 02:14 PM)mfleming Wrote:  BTW, with regard to the thread title, a microSD card or any flash device for that matter, would not be ideal for continuous use even as a ROM. Flash draws tens of mA current in use and so would be best for secondary storage.

When I saw this thread and the photo in the first posting I thought: Now this must be the most clever idea of the month! Use an SD card just as you would use a magnetic card (if you were lucky enough to find a card reader and cards). Plug it into the card reader, use the standard commands of the calculator for reading and writing and pull it out again.
128MB SD cards can be found for less than 1$/Euro/GBP on the internet, a lot cheaper than the few remaining magnetic cards.

What would it matter how many Milliamperes this cards draws during the few seconds that it is connected? The HP-71B has four (rechargeable) AAA batteries in it's belly, this is plenty for filling thousands of SD cards!

I would be more than willing to upgrade one of my HP-71Bs to a card reader replacement that accepts SD cards in lieu of magnetic cards. Unfortunately my embedded programming skills do not go beyond Arduino and this is clearly not sufficient here. A solution that requires a "PIL-Box" and some "Pil-software" running on either Windows or Linux (neither of which I have installed anywhere) and "LEX"-files of some kind in EPROM Modules is over-over-overkill for what is actually required here. But maybe I am just thinking too simplistic?

Regards
Max

[mfleming]

To be honest, my initial reaction was two-fold; Why would you want a removable SD card (when's the last time you took one out of your phone?), and wouldn't the card slide in at an angle? So I decided to try placing a microSD card in the slot - near perfect fit and it did go in parallel to the face of the 71B as the OP indicated in his third photo. So I'll have to admit, using a microSD card like it was a mag card would be kind of cool, especially given the greatly expanded storage capacity.

So, acknowledging the cool factor, how would you use such an accessory?

~Mark

[Maximilian Hohmann]

Hello!

(09-07-2022 06:54 PM)mfleming Wrote:  Why would you want a removable SD card (when's the last time you took one out of your phone?)

With the phone it really is awkward because in order to get to the SD card I have to remove the phone from it's case and then use a tool to pry the card out of the phone.
With my camera it is completely different. I have the choice of either using a cable or WiFi to transmit the photos to my computer but find it easiest to just remove the SD card from the camera and plug it into the computer.

(09-07-2022 06:54 PM)mfleming Wrote:  So, acknowledging the cool factor, how would you use such an accessory?

I guess I would reserve a couple of cards for the more often used programs (of which I have none at the moment to be honest... but maybe this is due to the lack - or awkwardness - of permanent storage available to me) and another one to tranfer programms for permanent storage on the computer. It would be easiest if programs would be stored as plain text files so that they can be edited on the computer using a simple text editor.

Regards
Max

[rprosperi]

(09-07-2022 09:28 PM)Maximilian Hohmann Wrote:  I guess I would reserve a couple of cards for the more often used programs (of which I have none at the moment to be honest... but maybe this is due to the lack - or awkwardness - of permanent storage available to me) and another one to tranfer programms for permanent storage on the computer. It would be easiest if programs would be stored as plain text files so that they can be edited on the computer using a simple text editor.

Regards
Max

Hi Max,

All of that is easy with a PIL-Box, which lets you easily move files back and forth, and with a bit of practice, it's nearly as easy to convert the programs BASIC <=> Text, though the 71B's need to use native (essentially tokenized) program code, it's still a bit of a pain, but that will remain true, regardless of the media. You can create a small script-like program which uses TRANSFORM to do the conversion on the device (not fast, and needs RAM) and then automate COPY commands to move the text file in/out.

And while I hope this discussion does lead to such a product, it won't be cheap in the small qtys involved. But I'll support anyone that makes them.

[Maximilian Hohmann]

Hello,

(09-07-2022 09:38 PM)rprosperi Wrote:  All of that is easy with a PIL-Box, which lets you easily move files back and forth, ...

Yes, but for that I need a computer and a box and my HP-71B and IL cables (impossible to find since quite some time). And software running on my computer which doesn't run on my computer.

I think in order to be really useful it needs to be contained inside the HP-71B without requiring any external connection or additional software.

(09-07-2022 09:38 PM)rprosperi Wrote:  And while I hope this discussion does lead to such a product, it won't be cheap in the small qtys involved. But I'll support anyone that makes them.

Let's see if the "usual suspects" have anything to say about it !

Regards
Max

[vassilisprevelakis]

(09-06-2022 07:13 PM)mfleming Wrote:  [quote='JanS' pid='163806' dateline='1662474226']
For the 71B you'd probably want to emulate an HP-IL peripheral controller and interact with the pyilper program on a nearby computer.

Hi Marc,

Unfortunately emulating an HP-IL peripheral controller may not be possible as the card reader interface is missing the !INT and OD signals (which exist on the HP-IL connector).

It can still emulate a card reader, pretending to read-in cards, which will be a bit cumbersome as you won't have a view to a file system but to a single file (on potentially multiple virtual cards).

**vp
http://www.series80.org