#retro-apple — Public Fediverse posts

Wild request but if anyone has a working logic board of a Classic of SE family, and a logic analyzer, can you send me a few captures like the ones I have in https://codeberg.org/arroz/MacDVI/src/branch/main/HOW_IT_WORKS.md? Try to catch the key moments, like a full line including h-sync pulses before and after, v-sync, and video polarity. I want to adapt MacDVI to those families mimicking a signal validated by the RGBtoHDMI but I’ve seen lots of inconsistent info on the intertubes. #retroApple

Look at this 1-bit art! John Calhoun is the best! #retroApple

I’m not the bragging type but I’m really happy with how well my MacDVI adapter works! 😃

I left v-sync between the Mac and the DVI output for another day but it doesn’t really seem to be a problem. #retroApple

https://codeberg.org/arroz/MacDVI

And then the infamous labyrinth! #retroApple

The swamps! 😍 #retroApple

Speaking about things that matter. Not sure why I can’t run it from the HD but floppy will do! #retroApple

Hey, look who showed up! Now if I remembered what to do with this. #retroApple

Well, it doesn’t like System 7.1 on this disk. TBF this was meant for an LC so I have no idea if it’s supposed to support the Plus. I installed it, huh, 30 years ago? The details may be a bit blurry. #retroApple

4MB! Imagine the possibilities! #retroApple

Well I didn’t kill it! #retroApple

Memory in! Still all in one piece. Now to take out the resistor. #retroApple

Memory out, it creaked and screamed but didn’t break! 😅 That was stressful! #retroApple

I will post the simple project I used to have another Pico generating a test video signal similar to the Mac one, after cleaning it up and documenting it, but please give me a few days since I've spent the long weekend writing all the documentation, cleaning things up and fixing a few bugs. 😅 Time to step outside and enjoy the sun. #retroApple #retroComputing

Introducing MacDVI, finally! 😁 Here's the ready-to-use binary, source code and a LOT of documentation on how to use a Pico 2 to convert your compact Mac TTL video signal to DVI! Bring new life to an old Mac with a dead CRT, or just enjoy it on a modern monitor!

There's extensive documentation on how the Mac generates the video signal and how MacDVI samples it. Hope it's good learning material for people interested in #retroApple #retroComputing!

👉 https://codeberg.org/arroz/MacDVI 👈

Question for #retroApple folks: I’m going to replace these 256K modules soon by the 1M modules (I know I need to remove the resistor). After 40 years, how brittle are the plastic hooks that hold these things in place? Should I be worried about breaking them when I pull them to release the modules?

Also, I'm currently cleaning up, heavily documenting the code, and fixing a few bugs, to make it public. More than a ready to use thing, I want it to be as much of a great learning material as I possibly can, so it can help people have the same fun and excitement learning and building things as I had myself! #retroApple #retrocomputing

After testing my TTL to HDMI converter on the Mac Plus logic board yesterday and seeing it working flawlessly 😁 I'm looking into the next phase of the project, and need help from #retroApple #retrocomputing folks. If you have any of:

-Mac 128/512/Plus analog board user-visible components (power switch, socket, battery holder and brightness knob, speaker) OR analog board (good or damaged, 120 or International);
-Mac Plus case/frame;

that you do not want, please ping me. https://mastodon.social/@arroz/116466320610054360

#RetroApple

Next steps are cleaning the code and pushing to somewhere public. Maybe it’s a good opportunity to try Codeberg? #RetroApple

The Pico is *very* overclocked, from 150 to 325Mhz. Not because of the sampling (although it helps!) but due to the required resolution on the DVI port (1024x768 for pixel perfect doubling). Sampling it entirely made with PIO, the CPU is just handling DMA interruptions to adjust read and write addresses. Tried a few implementations, most CPU based, but this was the final goal, and it works beautifully!

#RetroApple

The second Pico you see on the video is just a dev probe, it’s not doing anything. The Pico on the right is the one sampling and generating the DVI signal.

I still have to improve the 5 to 3.3V situation (it should be possible to do it with resistors only, hopefully) and a few finishing touches on the software but I couldn’t be happier!

Also it’s probably time to buy an external BlueSCSI. Poor Quantum lasted more than 30 years but it has its limits. #RetroApple

The 52MB disk apparently has decided 2026 is just too much. And the Mac does not have enough memory (yet) to boot from 7.1 that’s installed on the other SCSI disk. So we have to use the floppy. But…

Here’s a real Mac Plus booting of a floppy disk, with a video converter made out of a single Raspberry Pico! 😁 Still have to improve a few bits (the Mac sends random noise that messes the auto-adjust for optimal sampling) but look at it going! #RetroApple

HOLY DOGCOW it actually works! I’ve made something that works!!! #RetroApple

We’re entering crazy territory but yeah I’m borrowing the level shifters from the Guzman’s logic analyzers. Time to test with the real thing!

If I was careful I could actually connect directly since the Pico GPIO is 5V tolerant. But only when the Pico itself is powered! So… let’s do it with the level shifters just in case. #RetroApple

I stand corrected, the chip is fast enough. It’s the resistors that are not handling the high frequency and mess up the signal. #RetroApple

Here’s a fun one, I was trying to make sure the resistor based trick to shift from 5 to 3.3V worked but because my current generator is another Pico (that works at 3.3V) I’m using an HCT chip to bring it up to 5V. It works for both v-synch and h-synch but the chip can’t switch fast enough for passing the video signal properly, so the background checkerboard pattern turns to solid black! And you can see the slight delay it adds, as the image is shifted right a pixel or two. #RetroApple

Finally!! Perfect sampling! Still a bit of expected garbage on the vertical back and front porches but the sampling works, totally stable and pixel sharp! And even better, 100% PIO and DMA based! The only thing the CPU core is doing is pre-calculating a table with the sampling timing (based on Bresenham sampling) and adjusting the DMA addresses on interruptions. #RetroApple

Almost forgot, but the sample image I used for testing is not mine. Credit where it's due, it was downloaded from https://www.keacher.com/1216/how-i-introduced-a-27-year-old-computer-to-the-web/ #RetroApple

The horizontal offset is two pixels of what it should to display properly but meh it works! Those are things that can be easily adjusted if needed. EDIT: Also missing the first two lines of the image or so.

This took longer than it should but it’s hard to be dealing with such low level stuff in a language in a bit rusty at while learning a new platform, all after long work days. Try to calculate frequencies and offsets while almost falling asleep! #RetroApple