HP-48 FRAM Cards

[Dave Frederickson]

(08-19-2016 12:06 AM)JDW Wrote:  Seriously, from day one I was concerned about that FRAM card design (even the SRAM cards from that same seller) simply due to "static discharge." As you know, all the old HP and third party cards were made very well in that they were completely covered. Not only did that protect the expensive circuitry from death-by-static, but it also covered the PCB so your eyes are never distracted!

I can think of two possible solutions to the ESD issue.
1. Conformal coat the board. UR and AR conformal coating is available in spray cans. Don't forget to mask all the pertinant electrical connections first.
2. If spraying the board isn't your thing, you can apply Kapton tape.

Dave

[JDW]

(08-19-2016 12:20 AM)Dave Frederickson Wrote:  I can think of two possible solutions to the ESD issue.

Please don't suggest that to the seller, Dave. The price will likely go up $50! We need to find a way to make the FRAM cards drop in price! :-)

[Dave Frederickson]

(08-19-2016 12:32 AM)JDW Wrote:  Please don't suggest that to the seller, Dave. The price will likely go up $50!

Hi JDW,

The thought never crossed my mind. Next time a PM or email might be a better way to express your concern as the seller has probably read your post by now.

Dave

[JDW]

No doubt he is reading this thread. Which is why I dropped the ever so subtle hint that "lower prices" might yield "better sales."

I doubt he's offended. It's just business. If you can't sell at your preferred higher price, you simply offer a sale/discount.

I am thankful he exists though. He appears to be the lone soul on the planet who sells FRAM cards for the 48GX.

[matthiaspaul]

(08-19-2016 12:06 AM)JDW Wrote:  

(08-18-2016 09:56 AM)matthiaspaul Wrote:  I find the design and finish of that seller's cards somewhat distracting. There's so much that could be done better that I'm considering making my own design... (If I only had the time... ;-)

Maybe I should hold out for your edition then? :-)

Seriously, from day one I was concerned about that FRAM card design (even the SRAM cards from that same seller) simply due to "static discharge." As you know, all the old HP and third party cards were made very well in that they were completely covered. Not only did that protect the expensive circuitry from death-by-static, but it also covered the PCB so your eyes are never distracted!

So if anyone would kindly sell us FRAM cards at half the price of that EBAY seller, I think we could sell quite a few, with myself being first in line!

If I'd do it, these would be my design goals:

Mechanical design:

- thicker composite board 3D design to more closely resemble the original card dimensions. This will improve the stiffness of the card (to reduce the risk of damage by bending), it will eliminate "wobble" in the slot (for a better electrical contact, reduced wear of the connector contacts and longer life in industrial and/or vibrating environments), it will give a better and more secure grip when removed, and it will protect the "recess"-mounted chips from all too easy mechanical damage and being easily touched (ESD).
- possibility to fill the central recessed area of the card (where the chips are mounted) with epoxy to actually seal the chips - would reduce the ESD vulnerable area almost down to the card's contact area, but would make any repair impossible
- some kind of eject grip
- rounded corners
- (I spoke to a mechanical engineer about the possibility to design a spring-loaded flap to protect the contact area, but I doubt it will be possible to find an affordable solution for small batches)

Electrical design:

- 2 MB (if still possible to place with all the extras: 4 MB)
- high-quality FRAM chips (there are considerable price differences between chips up to factor 3: some of the cheapest chips I saw have read/write endurances of only 10^10 cycles, specified data retention times of about 10 years (at +85°C, though, but no specification for lower temperatures), and draw currents of up to 20mA active and 20µA in sleep, whereas some of the most expensive ones have 10^14 cycles, specified retention times of several decades (at less than +85°C, that is), and draw less than 12mA active and 8µA in sleep)
- better ESD protection (although perhaps not perfect)
- global hardware write protection switch
- reconfigurability to bankswitched memory for HP48SX compatibility (and to support 4 MB on 48GX without bogus error messages)
- micro-USB interface for easier and faster data transfer and card backup to PCs, possibly also as alternative power supply to save batteries (I would have to check HP48 schematics to see if this would be possible without modification) [EDIT: Unfortunately, an external power supply facility is technically impossible without a minor hardware modification in the calculator. A quirky and only partial solution would be a short external cable from the card to the serial port, but I don't think this would be very practical.]
- possibly integrated micro-SD card slot for local backups (peak power-consumption could be an issue - to be checked)
- possibly integrated wireless connectivity (BT? NFC?) (peak power-consumption could be an issue - to be checked)
- special power design to minimize power consumption
- quality placement and layout artwork adhering to established electrical design rules, not the result of some kind of wierd auto-placer and -router

Firmware design:

- Microcontroller emulating an USB mass storage device with virtual FAT file system to access the various HP ports
- Software configurable write protection of indivitual ports
- SD card could work as a "shadow" background storage medium to store "snapshots" of ports when set to read-only
- Possibility for a direct data channel to transfer individual values between a HP48 and a PC or smartphone application

Software:

- HP48 application software or library to enable/disable write protection and switch banks
- HP48 application software or library for directly transfer data

Finish:

- DIY parts kit? Self-assembled? Professionally made? Firmware / software a community project?

Greetings,

Matthias

[JDW]

Matthias,

I spotted your excellent post the day you posted it but I waited until today to reply just to see if anyone else would respond. No one did. So despite your excellent idea for a vastly superior FRAM card, it would appear that the only person interested in such a card besides you is me! That would indicate the 48GX users among us either already have cards and don't need another, it it means they don't feel they need one, or it means they've moved beyond the 48GX to the 50g.

Regardless, I still like your FRAM card concept very much and even if it was a DIY kit that required soldering I would still be interested, should such an item ever make an appearance in the future.

--James

[Han]

I would be interested in such a card (in fact, several) if the price was affordable. So that makes one more user.

[matthiaspaul]

Unfortunately, external power via USB is impossible in the HP48, as the card connector does not carry the necessary supply signal. It has two unused pins (card pins 38 and 39), so it would be possible to modify the calculator to connect this to "VBAT" (battery "+" and CPU pin 145), but I guess most users wouldn't want to open their calculator for this.

Unfortunately, I have no information about the internals of the Yorke chip, in particular the circuitry between "VBAT" (CPU pin 145), "VH/V+" (CPU pin 130), "VDD/VCC" (CPU pin 125) and "VCO/VCC-ON" (CPU pin 126).

It very much depends on the internals, but there is a slight chance that it is possible and electrical safe to either reverse-power the calculator through VCO/VCC-ON (which is available on the card connector pin 1) or through the 4-pin serial connector (which is connected to VDD/VCC via 75R, so that a cable could be connected between the USB-powered expansion card and the serial connector), but unless I know for sure, I won't try, as it could easily damage the calculator as well. However, it is possible that someone has already investigated this in the past...

Another important question to answer is how much current can be drawn by an expansion card through VCO/VCC-ON. Does someone know? Is this documented somewhere?

Greetings,

Matthias

[gege]

I also thought about creating my FRam card because the one available on ebay is too expensive (for hobbies usage), but currently I have no the time to do it, so your card interested me.
I was thinking to add GPIO to connect external hardware to the HP.
And perhaps an esp8266 module to have wifi connection.

I have 2 HP48Gx and one HP48G upgraded to 256Ko of ram internaly.

[matthiaspaul]

(08-25-2016 03:19 PM)gege Wrote:  I also thought about creating my FRam card because the one available on ebay is too expensive (for hobbies usage),

Of course, a 2 MB or 4 MB card would still be expensive (when compared with flash or SRAM), simple because FRAM is a comparibly expensive technology.
Prices could be reduced significantly by using older generation FRAM chips, but at the expense of significantly lower endurance (10^10 to 10^13 cycles rather than 10^14 to 10^15 cycles), a lower data retention time (although all chips still seem to allow 10 years) as well as a significantly higher power consumption. Since I see it as a one-time investment and this is a battery-powered device, I would tend to use the best chips available (within reasonable price limits), not the cheapest.
Things would be different, if we could use MRAM, as this is available in larger capacities and for much lower prices - however, all MRAM chip specs I studied so far also indicate a significantly larger power consumption in active mode than FRAM, and longer startup times, which would make it impossible to implement some power management schemes. So, they do not seem to be the ideal choice for battery-powered devices.

Quote:but currently I have no the time to do it

Same here.

Quote:I was thinking to add GPIO to connect external hardware to the HP.

I was thinking about that as well, but not in form of "raw" GPIOs on the card, but more by providing a connection to some external hardware and control GPIOs in that external hardware through some standard protocol. I2C would be a possibility, but TTL-serial might be a much better choice given that the HP48 already has a RS-232 interface, and I2C could be implemented only by indirect means. Having the GPIOs in an external hardware would also eliminate ESD and power supply issues.

(Sidenote: If I would design a 128 KB card for slot 1, I would try to include a port replicator for the LCD interface, so that it would be possible to use the overhead unit in parallel to a memory expansion card, or even better, reroute the outgoing LCD data through USB (or wirelessly) to display the LCD contents on a PC or smartphone display.)

Quote:And perhaps an esp8266 module to have wifi connection.

The main problem with WLAN is power consumption. The suggested module would consume 130 to 220 mA in typical use. That's way above of what I would want to draw from the HP48 - in fact, even though I don't know the exact figures yet, I doubt the HP48 can provide this much current without being damaged. In comparison, BLE is more like 10 to 15 mA - this is in the region of what I expect the HP48 is able to deliver on a card slot without problems. After all, the HP48 was designed to supply SRAM cards only.

(BTW. This may also rule out SD cards. Some SD cards can draw currents beyond 200 mA, although typically in faster modes only. I would find it unsuitable if the user had to select a special "low power" card for usage with the HP48 instead of using whatever is in reach. This wouldn't be a problem for as long as there is also a USB cable plugged in at the same time, but having a direct connection to a PC makes an SD card pretty much obsolete anyway. So, it seems, this combination of features does not make much sense.)

WLAN may also cause EMI problems.

Greetings,

Matthias

[JDW]

gege mentioned that his 48GX was upgraded internally, adding 128k to the existing 128k. How does that affect usage of cards in Slot 1? Is Slot 1 still restricted to 128k? And can a 128k card in Slot 1 still be merged with System RAM, yielding 256k + 128k = 384k?

Next, even if a wireless interface were added to this concept FRAM card, wouldn't the data throughput be roughly the same as what we get via cable anyway? If so, it makes little sense to invest the time, energy and expense to include it. The convenience benefit would be marginal at best. It would be more of a neato feature than anything else.

As to FRAM chip tech, I would agree that any new card design should use the latest chips, even if they are marginally more expensive.

--James Wages

[Ron Ross]

Do the FRAM chips share the same footprint and pinout assignments of the previous RAM chips used by earlier 48GX ram cards? It would be great if that were the case. Simply buy an older card and replace the RAM chip with a FRAM chip. It would also be a nice way to upgrade an older card (thinking of me, as usual!!).
.
However James, I believe I had recommended the Hp 48G series to you earlier when you were looking for an Hp 28s replacement. And I had warned you about buying the GX!
.
There was a German reseller who upgraded and overclocked Hp 48Gs. I believe Walter bought/owns one. I suspect he was satisfied with it. I kind of feel that if you are doing this for yourself, you might consider just buying an Hp 48G in excellent condition and doing that type of upgrade. I upgraded an Hp 48G in similar manner (did not mess with overclocking though). It was kind of tedious, but I used a SMT 128K chip and a 512K DIP with socket for the expanded memory. I kind of wished I had tried a 512K SMT directly on the board and tried to re-route the multiplexing pins. Why? Because my 512K cludge was always the bulky and poorly fitting ugly work of this project as I soldered my socket onto the socket joints reserved for the 48Gx ram card receptors via a ribbon cable. Why did I do this? So, I wouldn't damage a 512K ram chip and could simply pluck the RAM chip in later. However, I suspect I always had a cold solder joint or short as I would get the 512K ram chip to read correctly and work about 90% of the time ie it would look like it was working, but if I handled the calc I would often lose anything in the upper ports, no errors, just the loaded programs in the upper ports would be gone. My 128K SMT worked fine.
.
Regardless, I bought Klotz cards shortly thereafter and was very happy with his product versus my own workmanship. If you think about the hours you will end up investing in your own cards, I suspect you will begin to re-assess the value of these $200 cards.
.
Regardless, I was never enamored by any graphing calculator. I like my Hp 48Gs better than any other graphing calculator, but if I actually had to use the graphing capabilities, I would switch over to an Hp 50G pretty damn fast. No, I use it as a number cruncher. And truth be told, it actually isn't as good of a number cruncher as my Hp 42s for EE work (especially after I enter programs, however I got burned in the past by a memory reset on my beloved Hp 42s too). But the Hp 48Gs are easily replaceable, and much more versatile for ANY engineering work. So it is the tool I keep in my desk at work without regard to any work or office hazards.
.
I mention the last information to warn you of any significant investment to the Hp 48G series. It will appeal to a very small market. Very small. My own antidotal evidence is that 19 out of 20 Hp 48G users would be even more happy with an Hp 50G for the PRICE and extra features versus having to spend 2X for a calculator with 1/2 the speed and features. And the other 1 in 20? They are happy with their second backup calculator and either already have the cards or don't need them. Just my opinion.

[JDW]

Thank you for your reply, Ron.

Yes, I do remember your recommendation of the 48G over the 48GX. But after much thought and comparisons I nevertheless decided upon that GX. A lot of the prices I was seeing on eBay showed the 48G to be rather high. So if I paid a little bit more I would get more RAM and an expandable calculator too. That's why I ultimately went with the GX. I also purchased a refurbished 50g at the same time, and of course the 50g is superior in many ways to the 48GX. But to me it's not a waste because I can keep one at home and the other at the office.

Now let's get back to the question I asked in my previous post which so far no one has answered.

A previous poster spoke of adding 128k to the existing 128k in a 48GX. How does that affect usage of cards in Slot 1? Is Slot 1 still restricted to 128k even after you have 256k of onboard RAM? And can a 128k card in Slot 1 still be merged with System RAM, which in that case would theoretically yield 384k?

Why even talk about 48GX upgrades? Because, from what I see, many people still like the 48GX, and many surveying engineers apparently still use them too, keeping prices of cards high due to that demand. As such, I don't see FRAM cards being a worthless discussion that would benefit only 10 to 12 people. Sure, it wouldn't be "thousands upon thousands" potential buyers either, but FRAM card demand would probably be enough to warrant development as evidenced by the EBAY seller who spent time and money to develop his FRAM cards for the 48GX. He should have his 128k cards back on sale soon, but he doesn't sell large cards like 1MB to 4MB, nor is the design protected from static or accidental damage due to drops, hence the FRAM card "concept" presented by Matthias.

Because of its expandability, you can do more with the GX than with the G. We all know the HP48 is slow versus the 50g, but the full versions of Meta Kernel or Speed UI can make the 48GX into a very snappy machine, but only if you have the RAM. And that is yet another reason this FRAM card thread has merit. Sure you could just buy an SRAM card, but for me, I am getting older and less mindful of things with each passing year, such that I'd rather not have to remember to swap batteries on a card inside a calculator to avoid losing all its contents. An FRAM card using the latest technology chips solves that problem. And of course there's the "awesomeness factor" as well.

Some guys like to tinker with old cars. That never has been me. I'm a nerd. I love to tinker with vintage Macs, even using RetroBright to deyellow plastics. (Here are my Flickr photos. Here is my GCC Hyperdrive Mac 512k video.) And my love of the 28S led me a couple months ago to enter the world of the HP48 and 50g simultaneously. To me, FRAM cards make the 48GX exciting just as newRPL makes the 50g exciting. That's also why I love this forum, seeing my fellow geeks share the same excitement with me. It's great to see so many people love these old machines and keep them not only alive but kicking strong too.

Best wishes,

James W.

[gege]

I have upgraded my HP48G not the HP48GX simply because it's easy (no expansion connector). I remove the original 32KB ram and replace it with a 128KB and after I add another 128KB (on top) and connected it like an expansion card on Slot1. This ram is merged with the internal to have 256KB of RAM. Maybe I do the same (with begger memory size) on Slot2to store librarys, it's for that's I thinking about FRam.
HP48GX can be upgraded like this (internaly) but you lost the external slot usage, so it's preferable to use expension card.

I also have an HP50 but prefer to use my old HP48.

[matthiaspaul]

(08-26-2016 04:13 PM)Ron Ross Wrote:  Do the FRAM chips share the same footprint and pinout assignments of the previous RAM chips used by earlier 48GX ram cards? It would be great if that were the case. Simply buy an older card and replace the RAM chip with a FRAM chip. It would also be a nice way to upgrade an older card.

There are some subtle differences, but, yes, many FRAM chips use pinouts compatible with SRAM chips. However, the HP48 uses 5V CMOS technology and most modern FRAM chips are 1.8V to 3.6V, so you'll have to add level translators to use them in the HP48. I still found a few 5V FRAM chips, but they seem to be older generations and lower capacities only.

Greetings,

Matthias

[JDW]

A previous poster spoke of adding 128k to the existing 128k in a 48GX. How does that affect usage of cards in Slot 1? Is Slot 1 still restricted to 128k even after you have 256k of onboard RAM? And can a 128k card in Slot 1 still be merged with System RAM, which in that case would theoretically yield 384k?

James W.

[gege]

Upgrading the G or GX to 256KB is like to put a 128KB memory card in Slot1, so yes you lost the Slot1 usage and yes the memory can be merged to have 256KB of main memory.

[JDW]

(08-29-2016 05:32 AM)gege Wrote:  Upgrading the G or GX to 256KB is like to put a 128KB memory card in Slot1, so yes you lost the Slot1 usage and yes the memory can be merged to have 256KB of main memory.

Thank you for confirming that on an upgraded (256k) 48GX:

1. You cannot put any cards into Slot 1 anymore.
2. You can only use Slot 2 for cards.

[gege]

You can only use slot2.

[Han]

I still am not quite clear on the read/write cycles. While there may be more than 10 billion times the number of cycles as FLASH (according to an earlier post), what exactly happens during a read cycle? Does the entire content of FRAM get re-written? Or just the bits that got read? What happens when FRAM gets mapped to parts that get read frequently? For example, if the display data is mapped onto FRAM, then there are lots of read/write cycles without the user ever doing anything but having their calculator on. Can someone comment on this?