A Lisa Inside An FPGA

[AlexTheCat123]

I've given up on the speed selection switches for the moment. I was able to get it going so that the Lisa would run at double speed (40MHz DOTCK, 10MHz CPU clock), and you could tell that it was a good bit faster, but it wouldn't boot anything except the Selector because I somehow managed to break the floppy controller pretty badly. And no matter what I did, I couldn't figure out why it was broken. So I've reverted back to the version before the speed switches were added and started working on other things from there.

The good news is that I fixed the I/O board parity issue that was keeping the contrast from working in LOS! I just had the parity backward from what it should be, so inverting it fixed things and now contrast works fine!

And over the past few days, I've been trying to get USB peripherals working. I've written the full interface modules for both the USB keyboard and mouse, and the mouse one actually works! It's so cool to be able to directly control the Lisa with a modern mouse! The mouse scaling is a little weird and so I'm trying to come up with a good algorithm for making it slower without sacrificing small mouse movements, but that's a minor detail.

The keyboard, on the other hand, is still having some problems. The keyboard module took forever to write thanks to the Lisa's weird keyboard protocol, the challenge of converting USB HID scancodes to the key down/key up codes that the Lisa uses, and the weird way that the USB keyboard handles modifier keys like control and alt, but I think the logic itself is fully-functional at this point. The problem is that it doesn't work! After probing it with a scope and comparing it to a real keyboard (actually a USB to Lisa adapter since I don't have a real Lisa keyboard), I discovered that I'd actually gotten one of the timings waaayyy wrong, so I just changed that and now I'm re-synthesizing to see if that helps at all. It really seems like the keyboard module is doing exactly what it should other than that; hopefully this is the only thing that's wrong with it. Aside from maybe some keys that I mapped incorrectly!

[AlexTheCat123]

The USB keyboard works too! That timing issue was the whole problem. I've tested every key in LisaWrite and the only ones that don't work are the tilde, left option, numpad +, and numpad enter. Probably just a mistake with the scancode mapping, so any easy fix. And then we'll have a fully-functional USB keyboard interface!

[stepleton]

I believe I have experienced some strange mapping issues with my regular Lisa keyboard and tilde vs. option sometimes. Could be a coincidence, but you may want to check what you're seeing against real hardware.

[AlexTheCat123]

I believe I have experienced some strange mapping issues with my regular Lisa keyboard and tilde vs. option sometimes. Could be a coincidence, but you may want to check what you're seeing against real hardware.

Yep, you were right! The tilde and option weirdness is the same on an actual keyboard. So the only issue was the numpad stuff, which is now fixed!

My next task is getting the USB mouse scaling to feel right, which is proving to be quite a challenge...

[stepleton]

I haven't confirmed it, but there might be a difference in the behaviour of tilde/option when booting the Office System directly vs. booting via the Selector.

I base this suspicion on the fact that I can't imagine Apple would have shipped a LOS that swaps the keys like that, and I've observed it happen in basically-fresh LOS installs where the only thing different from 1984 is the presence of the Selector in the boot process.

If the Selector is indeed responsible, then the problem lies somewhere in here, though I have no theory that can account for why it should cause that trouble.