A2DVI: Apple II Digital Video

jeffmazur wrote:

I see you already have provisions for multiple fonts. Let me know if you're interested in supporting the font selecion protocol used by ROMX boards. Would love to see at least one more board out there that does that.

I saw the code for ROMX support in the analog VGA source base I used. It's still there but currently disabled for the A2DVI. My font selection support slightly differs from the original, due to the new "language switch" support. And I didn't fully understand what the "ROMX textbanks" were exactly meant to be doing. :D But it's certainly something that can be supported again. It's one of the topics where we could do with some help for testing...

CVT wrote:

Amazing work, guys! Are you sure you are not using a bootstrap paradox?

Thanks, yeah, not sure: I told Ralle several times, it couldn't work. But that was before finding the RP2040's two powerful slave FCUs (Flux Capacitor Units)... ;-)

@jeff, @michael: PM.

rjustice wrote:

I'm a little hopeful with you involved Macfly, that once this is finished off, then we might see some attempt to get a A/// version working.

Hahaha, the idea has crossed my mind. :) But with the A/// it always feels there's only three people interested in related projects (me included..). But, who knows...

Here's something I have added to the A2DVI firmware: optional debug/status lines - as an option in the configuration menu. It shows the status of all Apple II soft switches at the top (in the free space above the Apple II screen), and some extra data below: currently the execution program counter, the stack pointer and address of the most recent zero-page access. It's not an exact science, since you can't see every single address, of course. Originally this was meant to help debugging the A2DVI itself.

But I find it still interesting and useful even for A2DVI unrelated cases, e.g. when your machine doesn't boot or your program was stuck, and you wonder what the heck the 6502 was doing right now. It's also interesting to see what a running program is doing - for example, executing code from a a specific slot ROM, the main ROM - or when a program enables the AUX MEM soft-switches, in order to access the extended memory banks of the IIe.

Here's an example: shows the soft-switches are configured to "HGR" (hires graphics), "40 column mode" and "page 1". All other soft-switches are off. And below: current execution PC at $AF42, stack recently accessed at $1F8, zero-page accessed at $2E...

A2DVI_DebugStatus.jpg

That's not spcific to the HDMI output, of course, could be done for analog VGA in the same way. Just shows the PICOs direct 6502 bus connection is also useful for other stuff. A card like this could be turned into a little debug/tracing utility. It has access to every single memory cycle, every single address, every single data byte. Opens up possibilities, almost like in an emulator...