The original 576NUC+ case design was created by Steve Boswell (AtariAge: Mr Robot) who later released the STLs to the open source community, which I was able to modify to suit this new incarnation. This was also made possible through the use of a free online 3D CAD application called TinkerCad, a simple to use but very powerful 3D design tool.
 

New 3D Printer

I recently graduated to the Bambu Lab A1 mini 3D printer, and can now do some seriously good prints.

Previously I had been using an AnyCubic Kobra Plus that I picked up for ultra cheap as a customer return via eBay. It was good for getting my feet wet in 3D printing, but I got tired of constantly having to tweak all the settings in order to get good prints, and quite frankly the Bambu blows it away. And now I can do multi-color printing the easy way.

So the cases you see above are of my final design made on the Bambu printer.


3D Printing Station Update

I had to do some rearranging to make things fit into the allocated 3D printing station space in my shop, but in the end I think it came out quite well. And I also got serious with my filament storage, opting to use sealed containers with desiccant packs inside.

HeatSets are Out

In the previous 576NUC+ case design, the upper and lower halves depended upon heat set threaded brass inserts for the screws to screw into. However I wasn't thrilled about using these since they are very dependent upon correct insertion to avoid cross-threading issues. So in this new case design I've gone with screws and nuts, with both being recessed into the case halves, and black in color to make them virtually invisible.

I sourced these from McMaster-Carr, but probably something equivalent could be gotten at your local hardware store, not requiring a minimum purchase of 100.

P/N 91249A618  Black-Oxide 18-8 Stainless Steel Pan Head Phillips Screw, 4-40 thread, 1-3/4" long, pack of 100

P/N 90328A101  Black-Oxide Zinc-Plated Steel Locknut, 4-40 thread, pack of 100


Got Feet?

On the bottom of the case there are 4 circles showing the location of the rubber feet (Clear Vinyl actually). These reference circles were sized at exactly the same diameter as the feet produced by EverBilt which can be purchased either from Amazon or Home Depot.

P/N 158 724 1/2 in. Self-Adhesive Vinyl Surface Bumpers, 16-Pack


- Michael

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The clock is counting down, and in just a few hours it will be 2024 - a New Year!

So I thought before the change occurs I'd make one last blog entry, and of course it's going to be about my ongoing project the NUCplus4 daughter board for the 576NUC+.

So what's been happening?

Well I definitely lucked out with the FujiNet plug-in add on board, and it appears that it's first physical manifestation is good to go out of the box. After testing it for a couple of weeks now, it looks solid.

However on the actual daughter board there was one small correction that had to be made during testing and that has to do with the VCC for the PS/2 keyboard sub-processor (PIC12F629) which needs to go from 5V down to 3.3V. With 5V it was causing the A8Pico Cart to not be accessible via the USB connection. Drilling out the VCC pad and then running a short jumper wire will correct it on the present rev of the PCB boards I had manufactured, but in the long run the gerbers will get updated and the rev level will be incremented.

I also spent a good week working on case mods to create a new 3D printed enclosure for this new NUCplus4 version. And I gotta say it's looking pretty slick. Check out this quick video I did to  introduce it.

My 3D printer is not the best, or perhaps I just don't have it dialed in properly, but it still turned out pretty nice none the less.

This case is specific to the 576NUC+ with the plus4 daughter board and the FujiNet plug-in. As such it is 8mm taller than the standard case. Still very compact.

Currently I'm wrapping up the firmware development for all the PIC chips required to bring this system together, so that all aspects of control happen from the PS/2 keyboard. To make this a thing, it required two sub-processors, one on each board in order to recognize and respond to additional key shortcuts to control the SDrive, A8Pico Cart, and the FujiNet. The end result means you will find no physical switches on this new system - absolutely none! This aspect also played into making the case mods a bit easier to pull off.

I think I'll wrap this up for now and get ready to usher in the New Year. So my next post for the new year should hopefully be about the imminent public release of the system design, as well as a good demo video of the system in action.

Happy New Year everyone!

- Michael

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This is what the production unit looks like. Well at least the boards, I still need to rework the 3D printed case as well.

The NUCplus4-Main Board is now at version 1.5, having gone through two previous sample board runs and several on paper only design improvements. And the NUCplus4-FujiNet Plug-In Board is at version 1.4 due to several evolutionary advancements, although this is the first time its taken actual physical form.

It took me about 3 hours to build both of these, and then another few hours tweaking the firmware on the PIC chips to take it to where I wanted to go with the UI, which is entirely under PS/2 keyboard control - no push buttons, slide switches, or toggle switches.

I'm going to keep this blog post short, but I promise to reveal much more in the next one to come.

Stay tuned.

- Michael

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This project is suffering from a bit of feature creep, but it's all good and desirable stuff that's being added (trust me).

So because of also wanting to be able to incorporate at least the networking aspect of FujiNet into the project, a couple of extra headers were added, and a FujiNet Plug-In Module has been designed.

The PCB mock-up of this new FujiNet Module can be seen to the right. With the real thing nearly ready to have the gerbers sent off to the board manufacturer to get some sample boards made.

This is meant to plug in on the right of the A8Pico Cart module of the NUCplus4 daughter board. Taking advantage of the 576NUC+ internal SIO header, and a couple of small 2 pin headers on each of the bottom corners to stabilize the piggyback aspect of this module.

Everything from a WiFi aspect has been retained, so accessing TNFS servers, assigning remote files to virtual drives, and doing wireless printing to the PC is fully supported. However unlike the regular FujiNet implementations, SD Card access is separate being handled by the SDrive-ng.

For the firmware update aspect I chose to use a pre-made FTDI based RS232 Serial to USB-C board from AliExpress. Its cheap at just a tad over $3 (that price includes shipping), and has all the required signals broken out, including the ones that allow for Auto Program mode.

Being USB-C mimics the connector on the A8Pico Cart board, so only one cable need be stocked in order to load files to the A8Pico Cart, or to update firmware on either that or the FujiNet.

Individual physical switches have been eliminated for control of either the FujiNet, SDrive, or the A8Pico Cart, making use of the keyboard PS/2 signals broken out on the internal SIO header of the 576NUC+. This combined with individual PIC12F629 8-pin DIP 'slave' micro-controller chips on both the NUCplus4 daughter board and FujiNet module, allows all control to be done via the PS/2 keyboard. This method also allows for monitoring by the 'master' PIC16F1847 chip on the 576NUC+ so that certain actions can be modified and/or the present state displayed upon entering a key shortcut sequence. Having all actions controlled and coordinated by the single PS/2 keyboard, lets the 3D printed enclosure be much simpler and have far fewer holes, or any need for identification labels.

Speaking of having a PIC12629 on the NUCplus4 daughter board, yes that required a new board layout bringing it up to revision level 1.5.

I think that'll do it for this blog post. More to come...

- Michael

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AtariAge member electrotrains released his A8Pico Cart Project a few days ago on GitHub, and I've been busy integrating that into my design. Here's where things are at presently...

Everything is now 100% routed.

 I made a lot of changes on the component placement in the PCB layout, making it far more conducive to routing traces between components. This also altered the board shape slightly.

On the R-Time 8 aspect I changed to a larger battery same as was used on the original ICD variant back in the day (CR2430). I also have the power for this and the SDrive as an 'Always ON' situation taken from the 576NUC+ 5V Stand-By power connection, which is available from the internal SIO header. This means that so long as the NUC is plugged into wall power, irrelevant of whether the 576NUC+ is turned on, the R-Time 8 will run from the 5V power supply and not from its battery thus greatly extending the battery life. I wouldn't be surprised if the battery lasts for at least a decade with this setup.

Because the SDrive also gets its power in a similar aspect, drive assignments should be retained between power cycles.

Over the next couple of days I'll be double checking the PCB layout and schematics, and if all looks solid I'll be pressing the BUY button at JLCPCB soon after. Then when those sample boards arrive we'll see how or if I screwed up on something - always exciting.

-Michael

Update 9/13/2023:  I never pressed the buy button on this board version. After running some breadboard tests, and because of discussions in the A8Pico Cart AtariAge thread about protection circuits, and a change in direction on the SDrive aspect, everything changed. So much so, that an entirely different PCB layout was required, with the first sample PCB based upon this change having now been manufactured and awaiting assembly and test.

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Robin Edwards (electrotrains at AtariAge) has been at it again, and recently starting talking about an entirely new version of the 8-bit UNO Cart, only this time based upon a Chinese clone of the Raspberry Pi Pico. On this go around it has no removable media such as what the original UNO Cart utilized via its micro-SD Card, and instead it stores its files to an onboard 16MB of non-volatile Flash RAM, updated via USB.

Note: The Chinese Pico Clone is not a drop in for a real Pi Pico, having a different pin-out, as well as more I/O and more Flash RAM. The clone was required for this A8 version.

So I started thinking (always a dangerous thing), and decided to make something akin to an All-In-One daughter board module for the 576NUC+ project which would incorporate this new Pico Cart idea, along with several other very useful peripherals.

And here's a sneak peek as to what that may look like...

Currently I've assigned the moniker RPSX to it, which stands for the 4 main aspects contained within this module.

• R = R-Time 8
• P = Pico Cart
• S = SDrive
• X = XRAM (1024K extended RAM)

The Pico Cart does have ATR capability, but just like it's UNO Cart cousin this has some limitations, such as not being able to launch a CAR and an ATR at the same time. So it rules out doing something like launching Basic XE as a virtual banked cartridge and still being able to load and save Basic XE source files to and from the built-in file space. Hence the reason for also incorporating the SDrive.

BTW, the default 576NUC+ platform has absolutely no inherent banked cartridge support what-so-ever.

And while I was at it, I decided to give it the full 1MB of RAM, as well as a battery backed real time clock, making this a very well rounded upgrade for the 576NUC+.

Now on the surface it may look like I have this all figured out, but I presently don't have a clue as to what I/O pin goes to what on the Pico board until such time that the A8Pico Cart documentation gets released to the public, something that I have no idea of when that may happen.

Anyway stay tuned, and hopefully we'll see this project continue to come together.

- Michael

Note: The development on this project continued and got merged back into the 576NUC+ topic. Take this LINK to read more.

Although it's not a mandatory must have upgrade for the NUC, having dual Pokey stereo output would none the less be very cool.

Normally if this were a stock Atari 8-bit computer I'd say go with the modern plug 'n' play PokeyMAX in place of the original Pokey chip. However there are two reasons that won't fly on the NUC, one being an incompatibility with the TK-II chip responsible for keyboard input, and secondly there were some clearance issues. Because the 576NUC+ is an extremely condensed version of an A8, there simply isn't a lot of room between chips and other required hardware. And due to a wider footprint of the PokeyMAX vs. the Atari Pokey chip, this presents problems, one being a standoff for the FujiNet daughter board getting in the way.

So not being one to throw in the towel when the going gets tough, I started looking at some of the old school solutions, namely Gumby as originally proposed by Chuck Steinman of Dataque fame. In his proposal he outlined a method of stacking two Pokey chips and then adding a circuit for address decoding to let them share space. Here's a link to the article he wrote in December 1989 about doing that very thing. What Chuck really accomplished back then, was to create the standard for dual Pokey addressing that lives on to this day, over 30 years after its initial development.

In Chuck's design he uses a single gate from an inverter chip to invert the A4 address line for connection to the original 'left' channel Pokey chip's CS1 pin, and then simply routes the non-inverted A4 address to the same pin on the stacked 'right' channel Pokey. This gives a flip-flop action between which Pokey chip is enabled, dependent upon the state of A4. To finish off the circuit, the 'right' channel audio output was handled in a pretty simple way with the addition of a single resistor and capacitor, using trim pots to balance the stereo output between channels.

Looking at the original Atari 8-bit circuit, a pull-up resistor was connected to CS1 creating a high (logic 1) on that pin, which can be easily overridden by external logic. Unfortunately I didn't do that in the 576NUC+ design, so for my upgrade that pin needs to be lifted.

In my design I wanted to match the characteristics of the already present 'left' channel audio circuit in the NUC, thus having the same output level in both channels and eliminating the need for any trim pots. I also had to keep what I'll call the Gumby Interface circuit relatively small, due to the lack of space in the NUC. So for the A4 inversion I was able to use two resistors and a 2N7000 N-Channel FET.

Next decision was where to locate the circuit board in order to avoid a point-to-point wiring mess of the required components dangling in mid-air. And because there was a limited amount of free space available, I chose to create an XRAM piggyback PCB to give both a secure and stable mounting platform, as well as to pick up power, ground, and the A4 signal.
Note: XRAM is my abbreviation for eXtended RAM.

This method of both mounting the PCB via piggybacking the XRAM and grabbing the prerequisite signals from that chip ended up working pretty well. And although it would have been super nice if I could have taken the more conventional approach, and piggybacked the original Pokey chip along with using sockets instead of soldering the Pokeys together, this simply was not an option so a compromise had to be made.

Here's how it looks installed in the 576NUC+ (the system ROM and 512KB SRAM have yet to be inserted). It turned out pretty clean if I do say so myself.

And now with the hard stuff out of the way, I can connect my amplified stereo speakers, and then sit back and enjoy some Stereo Pokey tunes. Life doesn't get much better than that.

Oh just to be perfectly clear... this project is purely a personal pursuit and will not see a public release for the gerber files, or ever get produced by someone like The Brewing Academy.

- Michael

I had one of Mr Robot's early prototype NUC-XE cases which was patterned after its big brother the XEGS. However this was not designed with FujiNet in mind, and would require some careful modding to get it to work. But I really wanted to house my naked 576NUC+ with its proto FujiNet board installed. So out came the files, drill bits, and a hot knife.

Luckily there appeared to be just enough headroom to pull this off. Although it would require creating holes right where the top and bottom of the case joined up, which was a tricky proposition to say the least.

After a lot of careful pencil marks and filing, I was able to create the initial holes for the LEDs and push button switches, and finished it off by holding the case halves together while spinning a drill bit to yield a smooth circle.

For the SD card, I heated up an X-Acto knife, and made a rough cut smaller than required, which I then finished off with a file to the proper size.

On the rear of the case I ended up making a square hole with a file for the reset button instead of a round hole like I had done on the front. I did this because the lid has a lip with an extra thickness which would have required some carving out in order to allow clearance for the body of the push button switch. And although I did this for the front buttons and LEDs, it was a lot work.

I also did something similar for where the serial programming header needed to protrude, but had to make it bigger all the way around so that the serial USB cable's Dupont connector would slide all the way in.

Luckily since the body of the toggle switch sits farther back, I was able to make a round hole between the case halves, same as what was done in the front of the case.

Note: I use a Prolific PL2303 serial UART to USB cable for updating the ESP32's firmware, but a FTDI cable would work just as well.

Next came some ventilation holes in the bottom, since things did get a little toasty with only the angled vents on the top side.

The holes were started with a small drill bit, and then followed up with a Uni-Bit to the desired size. I was able to get a chamfer by lightly touching the top edge of the hole with the next increment of the Uni-Bit.

Identical holes were added to the other side of the case for a uniform air draw from the bottom to the top via convection.


I am very pleased with the final result, although in the future, proper cases with FujiNet in mind will get designed by Mr Robot for production. In the meantime my NUC is now safe in its cozy little home, and is dwarfed by the XEGS sitting below.

And for that added a touch, a proper label was placed in the space already provided for it.

I got this from Sticker You and ordered a sheet of them to share with the beta testers on this project.

Also found some very nice self-adhesive clear silicone feet at Home Depot.

- Michael

Normally these chips which are re-programmable, go for $5 each as seen in other eBay listings. And I had previously bought a few at that price point. However they're no longer in production, so what you get are NOS ones that someone still has a stash of tucked away. What makes them really nice is that you don't have to have a UV light source to erase them, since it's done electrically instead. Making for a much better and faster programming cycle.

Now I can get OTP (One Time Programmable) 512K EPROMS by Microchip/Atmel for about $2.50 in single quantities, and they are in current production. But being a one time programmable device means that you better get it right the first time, and be happy with it forever. However unless you plan on investing in a chip programmer such as the TL866 Plus, this may not be many peoples cup of tea. Luckily for the 576NUC+ there really is no need, since The Brewing Academy will be selling them with pre-programmed ROMs when they go into production.

The 576NUC+ system ROM contains two different Operating Systems, two versions of BASIC, and two games. It could be handled by a OTP device as mentioned, and for most people that'll probably be OK. But for a few of you who love to be able to customize your system, a re-flashable ROM would be desirable, hence the reason I was looking for an inexpensive and readily available source of these.

So I went in search for that cheaper EEPROM, once again going back to eBay. This time I found another seller for the SST EEPROMS that was advertising a deal that I knew was too good to be true, but part of me was game to find out for sure since the seller was only asking for about $1.00 a piece.

Here's that eBay listing.

About 2 weeks after my purchase I received the EEPROMS with all 20 pieces appropriately packaged in several standard IC anti-static plastic tubes. So far so good.

I then proceeded to plug them into my trusty TL866 Plus programmer and initially tried to flash them with the 64KB system ROM image for the 576NUC+, at which point, no real surprise they all failed one after the other.

Next I tried to erase a few of them, and once again no dice with the same error. So I tossed in a known to be good chip, and it programmed without issue. But then I noticed a crucial difference in the chip ID. The one from JK Parts showed 0X DA 08, whereas the working chip was 0X BF A4. So I checked my stock of good chips, and all of them returned the same ID (0x BF A4). Next I checked several of the chips from JK Parts, and they all had that different chip ID of 0X DA 08. Obviously the JK Parts chips were not really SST 27SF512s but something entirely different (what are they really??? - initially I didn't know - hint: see note at the end of this blog post for the answer).

So with that revelation, I scrutinized the appearance and labeling on the top of what I will now call a 'REAL' 27SF512, and compare it to a 'FAKE' 27SF512 better known as the chips I purchased from JK Parts on eBay. As can be seen below it's rather obvious that something is amiss with the FAKE chip's labeling. For one the numbering is way too crisp and clean, yet the SST label looks a bit rough around the edges. And although you can't really see it all that good in the photo, the depth of the indentation is much more shallow on the FAKE chip, as if someone sanded off some of the material (which they probably did in order to prep it for the new label). The printing is resistant to acetone, which was the strongest solvent I had on hand, and it might even be etched like the original would be.

So what's on the bottom of the REAL chip? Let's find out.

Yep that looks like something one would expect. Now let's check out the bottoms on those FAKE chips.

Oh yeah... that probably shouldn't look like that. Did the seller have a picture of the chip bottom on his listing? No certainly not. Apparently they couldn't be bothered to sand off and reprint the bottom of the chips like they had obviously done to the top side. At this point it was pretty clear that these were not genuine SST 27SF512 EEPROMs that I had gotten from JK Parts. But what could I do since the seller clearly stated "No Returns" on his listing.

This story has a happy ending...

Thanks to a AtariAge member Mr Robot's sleuthing skills, he matched the FAKE chip ID to a Winbond W27C512 EEPROM. And when I plugged those parameters into the XG Pro TL866 Plus programming app, everything fell into place allowing me to do multiple re-flashes of the chip as seen below.

So long story short, JK Parts sold me a relabeled Winbond W27C512 chip instead of the originally sought after SST 27SF512 I ordered. Both chips are EEPROMS, and they can both be repeatably re-flashed and erased. So bottom line I still ended up with a good deal that still works for my application, but I'll have to relabel the chips to avoid confusion. And now thanks to the seller's substitution I also know of an alternate chip for what I was originally looking for.

BTW, I was able to flash all 20 chips successfully as Winbond W27C512's.

However even though in the end this will work for what I need, I can't in my right mind recommend ordering from this seller without at least verifying what the heck is going on, although it's probably a case of Cha Bu Duo (aka: "close enough" - thanks to Mr Robot for that bit of insight). I won't be posting a link to that eBay auction, and I won't change the title of this blog post either, since it really is a fake, or in other words a substitution of another chip meant to fake the characteristics of the one it replaces..

- Michael

Since the procedure for loading cassette (cas) files is uniquely different for the NUC/FujiNet combination I thought it good to outline that procedure.

The following assumes that you have your FujiNet Program Recorder configuration set to use the 'Pulldown Resistor' option. This selection is made using the FujiNet web UI via a browser, and then  saving it.


NUC-FujiNet Cassette Loading Example

1. Select a cas file (e.g., O'Riley's Mine from FujiNet.online) via the config menu, press ENTER, and it will be placed in disk drive slot 8.
2. Press OPTION (F4) and hold it, then press START (F2) and hold it until the system reboots with the characteristic BEEP, then release both the START and OPTION keys.
3. To begin the file load, momentarily press the START key one more time... the RED LED will light up, and then just a tiny bit later the loading tones will commence.

 

- Michael