Atari ST or Amiga Mouse on 7800. Possible?

[Synthpopalooza]

I am thinking of writing a game on 7800 which would use the Atari ST or Amiga Mouse as a pointer. Would this be doable?

 

I found all this information for using such mice on the Atari 8-bit:

 

http://atariage.com/forums/topic/106973-mouse-on-800xl/

http://atariage.com/forums/topic/100282-standard-mouse-for-atari-8-bit/

http://lepix.cvs.sourceforge.net/lepix/lepix/mouse.asx?revision=1.3&view=markup&pathrev=MAIN

 

The other question is, would both mouse buttons be readable?

[RevEng]

I haven't tried myself, but looking at the pinouts I'd say that mouse movement and the left button look quite possible . Given that the 2600 and A8 can use them, I'd be surprised if the 7800 couldn't do it as well.

 

The second mouse button is iffy. Its connected to a paddle line, which is good. But the second mouse button would need an internal pullup resistor to be reliably/repeatedly used with the 7800/2600/A8 paddle line. I have no idea if the ST or Amiga mouse has one or not.

[Synthpopalooza]

ST does not but it can be modded for such while maintaining ST compatibility. Amiga, no idea.

[Trebor]

Trak-ball support possible too? Being essentially a mouse with the Axis inverted, if it helps, there are some schematics in the spoiler below:

 

 

 

 

 

The file named 'block diagram' in the above spoiler (First image) is the original Jan 84 schematics for a 7800 trakball.

 

The others ('CX22-Patch' & 'TTL') are self-explanatory and perhaps leveraged for the 7800 Trak-ball the Video61 sells with the independent fire buttons.

[gambler172]

I can hook a PC mouse on my 7800

[RevEng]

I'm no wiz with circuit diagrams, but it looks like the 2 buttons on the 7800 trackball use 7800 2-button mode. (unsurprisingly) The ST/Amiga mouse would need to use the 7800's 2600/single-button mode, and read one paddle input for button 2. (providing that pull-up is in place).

 

It's worth mentioning that the trackball (in arcade mode), the ST+Amiga mice, and the 2600 driving controller all use 2-bit quadrature encoding for each axis' position encoding. Support for one could fairly easily be modified into support for another.

 

I believe you'd need to sample the codes fairly regularly for the trackball and mice - maybe setup an NMI for each visible zone, and run the code there. After the delay from one visible screen to another, you'd wouldn't use the first code to position-update, but just as a "previous value" for comparing against the next fetched code for the position-update. That effectively throws away any motion that happened during the non-visible portion of the TV frame, but I think the position updates during the visible screen should serve to capture the overall motion pretty well, without severely limiting the CPU available to the game.

 

The driving controller is fairly coarse and you turn it a lot slower than the other devices, so it can usually get by with checking and comparing codes once per frame. That's how 2600 games usually do it, anyway.

[Synthpopalooza]

The game is not going to be CPU intensive. It's a 2 player chess like board game so you're only going to be pointing and clicking to move pieces.

[Synthpopalooza]

I also have an Amiga mouse so i can test the buttons on real hardware to see if they register.

[EricBall]

I did some proof of concept work in the past which might be useful: http://atariage.com/forums/blog/7/entry-140-dli-sampling-proof-of-concept/

 

See also http://atariage.com/forums/topic/68937-7800-centipede-trak-ball-conversion

[Lynxpro]

Trak-ball support possible too? Being essentially a mouse with the Axis inverted, if it helps, there are some schematics in the spoiler below:

 

 

7800trakball-blockdiagram.png

7800trakball-cx22-patch.png

7800trakball-ttl.png

 

 

 

The file named 'block diagram' in the above spoiler (First image) is the original Jan 84 schematics for a 7800 trakball.

 

The others ('CX22-Patch' & 'TTL') are self-explanatory and perhaps leveraged for the 7800 Trak-ball the Video61 sells with the independent fire buttons.

 

 

Video61 only rigged those CX80s to have an independent fire button. It doesn't have any other mods to it that GCC designed for the original CX22. And it certainly won't work as a native Trak-Ball with the commercial original 7800 Centipede either which is why it's rather dishonest to call it a "7800 Trak-Ball".

 

For the record, Dan Kramer - creator of the CX22 and the CX53 - highly dislikes GCC's hack there and believes it wouldn't have been cost-effect either in 1984 or 1986.

Edited August 5, 2017 by Lynxpro