Wednesday, February 13, 2013

More Results

Hey...just a guick update with a couple of links...

PALpable Interest

I found some helpful Dragon folks that were interested in this project.  One of them ran the code on his PAL Dragon and posted the results on this thread.  Surprisingly enough, the code seems to more-or-less work "as is".

I know that the PAL CoCo's and Dragons use the same (NTSC-only) 6847 VDG chip as the NTSC machines.  They have added circuitry that basically puts the VDG to sleep while extra lines are added to drive the PAL display.  I had presumed that those extra horizontal lines would be visible to the software, but apparently that isn't true.

I guess the lack of visibility for those extra lines is good news for this project.  OTOH, I had thought that the horizontal sync signal could be a good timing source for sound/music playback.  Now I would guess that those extra "invisible" lines would break any code using the horizontal sync signal for music playback.  So, if I ever want to support PAL machines in some future music-enhanced version of Fahrfall then I will have to find another way to make it work...

Show Me, Show Me, Show Me!

I posted a few more examples of pics displayed using the 44-color technique on my CoCo.  They are available in an album on my Facebook page.  Have a look!

Saturday, February 9, 2013

Back At It

Hey...anyone still there?  Oh, yeah?  Awesome...

CoCo Coding Contest

There is a coding contest in progress for CoCo enthusiasts, with the winner to be picked at this year's CoCoFEST! in Chicagoland.  You know that I can't sit that out!  But what to do?

After a little thought, I decided to use my 44-color display mode as the basis for a sliding puzzle game.  I doubt if that will be the most amazing CoCo game ever, but at least it should earn me a ribbon for participation... :-)

Prep and Clean-up

I left the code for this project a bit undone last Summer.  It would load in my local environment, where I use a monitor program over a serial port.  But it wouldn't load under a normal Color BASIC-based environment on the CoCo or Dragon.  I took a little time today to relocate the code and generate the necessary images for loading the code in such an environment.

Want to PAL around?

The code for my 44-color display mode counts display lines in order to coordinate VDG register changes with which lines are currently being displayed.  This counting requires the code to know how many lines are displayed in each frame, and that number is different between NTSC and PAL video modes.  I only have NTSC CoCo machines, including my Tano Dragon.  So, I don't have any way to test PAL-aware code.

If you are using PAL hardware and you are interested in seeing my 44-color mode in action, then maybe you can help me?  It should be as easy as increasing the number of non-displayed lines to count, but that number might need to be tweaked a bit depending upon exact cycle counts and such.  If you want to help me figure that out, then let me know!

For everyone else, watch this space while I roll-out my 44-color sliding puzzle game!