SFF 320XE - "designed in Sunnyvale California"

[Spanno]

Following on from the USB Keyboard Controller I hacked together for my Atari 800XL, I've now built this to replace the 800XL (which was making my desk look untidy):

 

 

I've named it "SFF 320XE" (SFF - "Small Form Factor" - it's 4" square).  Specs:

 

• Original Atari LSI
• Couple of ATF22V10C for the glue logic
• 512 KiB SRAM (320 KiB is decoded)
• 32/64 KiB E(E)PROM for the OS and BASIC
• Pico / RP2040 board provides the USB keyboard interface
• S-Video connector and 3.5mm audio jack

 

Audio/Video and SIO signals are exposed via a couple of headers.  I've built an A/V card, copying some elements from @mytek's 576NUC+ audio and video circuits (no vgate because I have a RetroTINK that will crop the video display as desired).  I plan to design an SD card adapter for the SIO header next (the RP2040 has a spare core that needs something to do!).

 

Some more pics:

 

Lashed up to a FujiNet:

 

 

Credits - this forum is awesome - I've learnt a lot lurking here for the last few years.  In particular, the Atari 800XL and @mytek's 576NUC+ schematics, and, @shoestring's memory tester have been invaluable getting this thing designed and debugged - thanks.

 

The hardware design files, schematics, gerbers and supporting source code are here (if you're so inclined): https://github.com/dpicken/atari-hw

Edited September 15, 2023 by Spanno

[_The Doctor__]

PBI / CART or bust

[reifsnyderb]

No PBI?  😢😢😢

[+x=usr(1536)]

1 hour ago, Spanno said:

Following on from the USB Keyboard Controller I hacked together for my Atari 800XL, I've now built this to replace the 800XL (which was making my desk look untidy):

Very cool!  A few questions:

1 hour ago, Spanno said:

• 512 KiB SRAM (320 KiB is decoded)

Why only decode 320K?  I'm guessing that it's using the RAMBO method of adding 256K to the board, but the whole 512K (or more) should be possible unless there's something I'm missing.

1 hour ago, Spanno said:

• 32/64 KiB E(E)PROM for the OS and BASIC

Does this arrangement allow for user-selectable OSes?

 

The lack of a cartridge port and PBI is understandable given the form factor, but are these something that could be possible by way of breakout cables or similar?  Echoing everyone else's opinions, they should be there if it's feasible.

 

Really nifty, and I've been pondering something similar myself.  Nice case, BTW 

[+mytek]

@Spanno that looks very nice, and is even more compact than the 576NUC+ that I designed. Great work 👍

 

At 4"square that matches the footprint of a 'real' NUC computer.

 

54 minutes ago, _The Doctor__ said:

CART or bust

 

[Spanno]

PBI, carts and more memory - maybe at some point.  BITD I had a 65XE and a small collection of games on cassette, so 40 years later a SIO port, some ATRs and 320 KiB is killing it for the moment :).  

1 hour ago, x=usr(1536) said:

Why only decode 320K?

It's simply as far as I've got.  Currently only Rambo mode is working.  I'm hoping the most recent revision of the board will support 130XE and 320 compy - but I've not finished debugging the PLD code for that yet.

2 hours ago, x=usr(1536) said:

Does this arrangement allow for user-selectable OSes?

Again, not yet.  I'm planning to use an RP2040 controller with more I/O for the SD card adapter and it'll have some spare I/O, so it's doable.

[Spanno]

1 hour ago, mytek said:

Great work

Thanks!  Your NUC inspired me (I have two 😀).

[+MrFish]

What's so great about Sunnyvale, CA?

 

[+Larry]

Perhaps I missed it, but how do you currently do I/O?  I saw the mention of an SD card, but can't see it in the pics. Maybe the little daughter card at the upper left?

[Spanno]

Right now I have it lashed up to a fujinet (see the final pic in the first post). 
 

Custom SD card adapter (and software to drive it) is the next task, it’ll plug into the RP2040 and SIO headers, here’s a mock up:

 

[_The Doctor__]

put heat sinks or, maybe a fan tunnel around all that. we already have heat related issues on some of these condensed version Atari 8 bit projects.

Edited September 15, 2023 by _The Doctor__

[Jfcatari]

Nice work!

 

Sounds like I have more projects on my plate to explore now.

[Jfcatari]

I am very interested in getting a few of these built from a doner 600Xl I have.

 

What version of your board do you suggest I work with?  1.2?

 

 

 

[Spanno]

Yes, 1.2.  The SD card adapter is still a work-in-progress, so you might want to hold off building that (I'm using a NUC FujiNet in the interim).

[+mytek]

I just figured out that your clam shell case is made from what appears to be PCB material. What a great idea 👍

 

 

I did kick around this concept for doing the back panel on the 1088XEL, but my PCB software couldn't create inner slots which was needed by some of the later I/O options.

[Spanno]

Yep, two blank PCBs. The lid has the logo on the top copper layer (enig gold plated) and the base has it on the silkscreen (to avoid shorts, should it come into contact with the rear side of the motherboard).