LisaList2

Good thought, Alex. Wouldn't hurt to try! The foam is still present both front and rear, it's just permanently compressed to perhaps 50% of its original height.

I know very little about the physical construction of Twiggy drives (I've never even seen a Lisa 1 in person other than in museums), so there might be a really obvious reason why this wouldn't work, but could you try pressing down on the disk with your finger to simulate the foam pad and see if that fixes all your problems? That way, you don't spend a bunch of time trying to find replacement foam if the problem ends up being something else entirely.

That is an impressive assessment of foam function, with the data to back it up! Thank you, sigma7.

This particular drive has trouble reading and writing disks with consistency. I have several new old stock 3M FileWare disks that work just fine in other Twiggy drives, but not this one. Generally, the Lisa prompts me to format / initialize the Twiggy disk and it fails halfway through the initialization process - LOS complaining that either the disk or the drive may be damaged. Sometimes, though, initialization completes successfully and the disk mounts on the desktop as normal. After a reboot or two, the disk inevitably fails to read properly and I am prompted to initialize it again.

Rinse, repeat.

My amateur brain guessed that ICs on the analog board that amplified the signals from the read/write heads might not be working properly, too weak for the old media in most cases, and that replacing those ICs would fix the issue. I replaced every IC on the analog board and... nope. Same behavior persists.

So, it seems there's another reason why it's not reading and writing the disks consistently. The foam is the only thing that's obvious. Otherwise, the drive is clean, has a new drive belt installed, and appears like it should be working fine.

When I first started working with Twiggies ca. 2008, I found the foam pads on the froggy only interfered with reading Twiggies due to increasing jacket friction, making it more likely the drive belt would slip, so I removed or disabled them.

However, as mentioned elsewhere, I've found one older Twiggy disk that turned out to be much more readable with the foam in place (for the front/lower head). (I've also mitigated the belt slipping issue which may or may not be relevant here.)

I don't know if the important effect of the foam was to affect speed variation, the angle across the head, or some other dynamic or geometric consequence. Perhaps it was subtly correcting a warped jacket or liner of this particular disk.

Incidentally, the way I discovered this was by pressing on the jacket beside the front head with my finger, experimenting with how the angle of the media crossing the front head affected read success.

So although I still postulate that it is better for media longevity to not use the foam (and no other floppy drive design uses it as far as I know), I admit there are circumstances where having the foam is useful.

My perception is that the foam is among the "softest" I've ever seen, so I tried the softest foam I had on hand and found it worked for the troublesome disk.

Hence this may not reflect the original specs of the foam, but it is what worked for me for the one particular disk.

The original foam is open cell, clearly low density and very soft to the touch.

The material I have on hand that is most similar is 5mm thick with adhesive on one side. This thickness seems about right.

I cut a rectangle out of it, slightly undersize for the front recess in the froggy: about 7.5 x 23mm

I cleaned the froggy with IPA and the adhesive already on the foam was sufficient to attach it.

I didn't apply foam to the rear position as this particular problem disk read fine with just the front foam.

So... how to characterize a random piece of foam?

I cut a length to make about 2 cubic cm of foam and weighed it on a scale having a resolution of 0.001 g but unknown accuracy:

0.070 g (with adhesive) (0.103 g with adhesive and backing paper)

which makes the density about 35 mg/cc

I might be able to manage a compression test to estimate the force applied by the foam.

Quote from: coffeemuse on January 12, 2026, 04:54:57 PMGood luck with the SDIO testing on the next iteration of boards. I am looking forward to seeing how the floppy emulation progresses.

Thanks! I really hope I can get it working; it would be nice to have an open-source alternative to the Floppy Emu out there. Granted, mine will probably never support 1.44MB disks, but at least it would do 400K, 800K, and maybe/hopefully even Twiggies.

Quote from: AlexTheCat123 on January 12, 2026, 04:07:24 PMAll this to say that the relocation of the buttons will probably be an issue for further down the road when I'm sure that they'll actually be on the board to begin with. And if the floppy emulator ends up working out, then I'd probably stick the buttons and OLED (along with the power, reset, and other control switches maybe) on a little breakout board that plugs into the mainboard with a ribbon cable. Then you can just screw that to the top of your (presumably 3D-printed) enclosure. How does that sound?

That sounds like a great approach. A breakout board with a ribbon cable would make enclosure design much more flexible. I wasn't trying to request any design changes; just wanted to confirm what enclosure considerations were on the radar.

I've had a 3D-printed case with 1980s-era aesthetics in the back of my mind, so that setup would work really well down the road. Good luck with the SDIO testing on the next iteration of boards. I am looking forward to seeing how the floppy emulation progresses.

Quote from: coffeemuse on January 12, 2026, 07:23:40 AMI noticed the OLED display, buttons, and switches for floppy emulation are mounted on the top surface of the PCB. I totally get that this makes sense for prototyping and early testing, but for those of us thinking about eventually housing a finished board in some kind of case or shell, are there any thoughts around this?

I honestly haven't thought about that at all! The floppy emulation is still in a really preliminary stage, so I'm not even sure if I'll be able to get it fully-working yet, and if not then those parts won't even be present on the final board. I think I've got all the code written to do floppy disk reads properly, but it hasn't been tested yet, beyond making sure the DC42-processing stuff works and that conversion to GCR and loading the data into the RMT is working properly. I can't test it until I get the v2 boards since I only have enough RAM to hold 2 sectors at a time (they take up a lot more space when in RMT format, a full 4 bytes of RAM per flux transition), which means that I have to access the SD card a lot, and SPI just isn't fast enough for this. So I need SDIO, which will be present on the v2 board.

All this to say that the relocation of the buttons will probably be an issue for further down the road when I'm sure that they'll actually be on the board to begin with. And if the floppy emulator ends up working out, then I'd probably stick the buttons and OLED (along with the power, reset, and other control switches maybe) on a little breakout board that plugs into the mainboard with a ribbon cable. Then you can just screw that to the top of your (presumably 3D-printed) enclosure. How does that sound?

Hi Alex,

Quote from: AlexTheCat123 on January 09, 2026, 09:24:35 AMIf anyone has any suggestions of other stuff to add/change on the v2 board, I'd be happy to listen!

Taking you up on your invitation for v2 board suggestions! This is more of a question than a suggestion, but I'm curious about enclosure options for the standalone board.

I noticed the OLED display, buttons, and switches for floppy emulation are mounted on the top surface of the PCB. I totally get that this makes sense for prototyping and early testing, but for those of us thinking about eventually housing a finished board in some kind of case or shell, are there any thoughts around this?

Specifically:

• Is there any consideration for providing headers to allow these controls to be relocated/extended?
• Are they positioned with any particular mounting orientation in mind?

Totally understand if this isn't a priority right now given everything else on your plate. I'm curious if it's on the radar.

Quote from: Jacexpo on January 10, 2026, 06:06:48 PMOpinions on what's wrong with the second memory slot?

I'm betting on a flaky connector right now. He bought the RAM slot connectors from Aliexpress, and the quality might not be all that great.

Quote from: stepleton on January 09, 2026, 01:55:03 PMDon't go out of your way on my account at least! This seems like a good option to me.

Happy to chip in to the development fund.

Perfect, that's exactly how I'll do it then.

And thanks so much for the offer! Maybe I'll PM you as I get closer to being ready to order the boards.

Quote from: coffeemuse on January 09, 2026, 05:15:55 PMIn the meantime, I would be happy to contribute toward offsetting some of the costs for your next board run. Feel free to send me a PM and we can work out the details.

Thanks again, I sure will once the time comes!

Quote from: coffeemuse on January 09, 2026, 05:15:55 PMIf you end up doing a bulk order for the final standalone boards, I would definitely be interested. I would be thrilled to have one of these sitting on my desk someday. Thanks again for all your hard work on this!

Yeah, hopefully enough people will be interested for the bulk order idea to work out. Obviously it's not very useful if only 10 or 15 people say they want one!