Colecovision > MSX

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By Grauw

Ascended (9737)

Grauw's picture

20-03-2014, 22:39

Looks sweet! I’ll take one (NL).

By jltursan

Prophet (2476)

jltursan's picture

20-03-2014, 23:18

Count me in, I want one!

By msxrestarter

Master (222)

msxrestarter's picture

21-03-2014, 00:50

Looks great, I want one !

By gdx

Enlighted (4247)

gdx's picture

21-03-2014, 04:54

ericb59,

The version of Pepper II from Muffie has some bugs in GFX and some sound effects have missing. It's not a good idea to put this version in a cartridge.

hbarcellos,

My work is based on Mission at start. At first I debugged and improved all Mission routines. Graphic and input routines are very different now. Sound routines have little changed. I also modified the interrupt routine (that I do not yet fully understand).

My process is as follows:

  • Of course I seek all access to the VDP to ports (IN, OUT, IN _,(C), OUT (C),_ INI, OUTI, IND, OUTD, INIR, OTIR, INDR, OTDR), joystick and sound calls in game ROM.
  • If the game still does not work properly then I place DI & EI instructions in sensitive areas. I also try to optimize some routines.
  • If the game still does not work properly again maybe it is caused by register mirrors, RAM address mirrors or interruptions problem.

The differences between ColecoVision and MSX harware:

ColecoVision

  • Main interrruptions are /NMI (caused by the VDP)
  • VDP it is same that MSX1 but I/O access is #BE/#BF (the mirrors do not seem to use)
  • Joystick status: It is easy. Write any value to #80 or #C0 and read port #FC or #FF. (Be careful at mirrors)
  • Sound chip: It is a SN76489AN. PSG with 3 sound voices + 1 noise voice. Used port is generally #F0 but there are mirrors used. Sound routines must replace some OUT of the Colecovision.

MSX

  • All interrruptions are /INT
  • VDP I/O ports is #98/#98 (Be careful at register mirrors that do not exist on V9938/V9958)
  • Input status: To play converted games on MSX, We need use keyboard and optionally joysticks. This is managed in the interrupt routine in Mission.
  • Sound chip: It is a AY-3-8910 (or a YM2149). It is a different PSG with 3 sound/noise voices.

The biggest problem is to adapt a /NMI to /INT configuration. Sound and input routines shift the progress of the program.

Where can I find your source code? Perhaps We can do better with our combined work. Perhaps it is possible to mix 3 PSG voices + 1 SCC voice. Mission use 3 PSG voices or 4 SCC voices. Only the following games use 3 voices on ColecoVision:

Donkey Kong
Donkey Kong Jr.
Mr. Do!
Roc'n Rope
Sammy Lightfoot

By andrea.denara

Expert (67)

andrea.denara's picture

21-03-2014, 08:44

Hi,
please take a look to
http://www.youtube.com/watch?v=vqFG_SGw6n8
this is Coleco PacMan prototype.
It's a must have for me, first of all is Atari game, second there's more than 4 sprites without flickering on the same line.
Unfortunately it doesn't go on Mission emulator.
If someone has some ideas to run it on a Msx....

Thanks

By hbarcellos

Hero (625)

hbarcellos's picture

21-03-2014, 13:23

@gdx
Here's the source code. You can find the SN emulator and the Keyboard/Joystick routines there. Let me know if it's working.
I converted Pepper 2 in 1 (one) day. Using the package that I had created for Tutanhkham.
I really don't believe there are sounds missing. Probably what happened is that noises sound like regular tones, but, as far as I can remember, there's nothing missing.
About the GFX bugs, can you give me some example? I would love to fix those before Eric ships the cart...

@andrea.denara
Do you have the Coleco ROM? Can you send me...

By ericb59

Paragon (1046)

ericb59's picture

21-03-2014, 13:47

Just one thing… In the aim of building a Cartridge set with other coleco Games, using SCC sound chip is not a good idea.
Because if you use SCC chip, you must use a SCC chip in the same slot as the ROM… Thus, in the same cartridge !
At this moment... the only way to do this is butcher Konami SCC cartridge ! No way for me !

By Manuel

Ascended (17747)

Manuel's picture

21-03-2014, 18:02

You may also find some (new) old stock of Konami SCC chips. The original Mega Flash ROM SCC was made with them.

By gdx

Enlighted (4247)

gdx's picture

22-03-2014, 03:37

Thank hbarcellos (Miffie ? andrea.denara ?) for the source code.

hbarcellos wrote:

About the GFX bugs, can you give me some example? I would love to fix those before Eric ships the cart...

The GFX bugs occur randomly when a stage display. Sometimes some characters appear at wrong place.

It even happens that the stage can not be clear because of it.

I had the same problem with several games. This is a problem of interruptions.

hbarcellos wrote:

Do you have the Coleco ROM? Can you send me...

I send it soon (with my conversion).

PS: Pepper II uses little the fourth voice so it is not very annoying..

ericb59 wrote:

Just one thing… In the aim of building a Cartridge set with other coleco Games, using SCC sound chip is not a good idea.
Because if you use SCC chip, you must use a SCC chip in the same slot as the ROM… Thus, in the same cartridge !
At this moment... the only way to do this is butcher Konami SCC cartridge ! No way for me !

I agree. If we exclude the SN76489AN I think the best way is a mix of 3 PSG voices and a optional SCC voice for the noise (A voice played by a SCC cartridge in another port.).

There are other more complicated solution: Switching a voice of AY-3-8910 when there is a noise.

By gdx

Enlighted (4247)

gdx's picture

22-03-2014, 05:21

gdx wrote:

PS: Pepper II uses little the fourth voice so it is not very annoying.

I was wrong. Peper II does not use the noise voice. I left the SCC sound in my conversion because I thought the music less aggressive thereby.

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