Hi Glenn!
>>Does this make any sense to you hardware guys? :-)
>Since the 2600 has no interrupts, and no input buffer,
it's hard to do truly
>reliable general purpose I/O.
But what I want to do is 'special purpose I' only :-)
>I think you'd be better off building a MIDI interface
on the cartridge
>itself and maybe having a chip on the cart
automatically write to a RAM area
>(it can be read-only to the VCS, but read-write to the
chip on the
>cartridge). That way the RAM area can act as a FIFO
buffer and you can
>process the MIDI data that accumulates during VBLANK.
>You'd have to have a hot address the 2600 can hit to
indicate that it's
>processing the buffer (so that any new data gets put in
a secondary area if
>necessary) and another hot address that tells the chip
to clear the ram and
>copy the secondary buffer data back to the main buffer.
I see your idea... Hm... I'm not sure if I should like
it or not. It's too much cheating somehow :-)
Next step would be placing the TIA inside the cartridge
too, and throwing the VCS away :-)
One thing, that is part of my current concept, is that
no video output is necessary at all, not even a TV is
needed. So I don't need to care about VBLANK or any of
that stuff. I can use _all_ cycles for
decoding/processing.
>Along the line, the chip in the cartridge could
possibly do some
>pre-processing of the MIDI data so that it is presented
to the 2600 in an
>easy-to-digest fashion. For instance, you could pre-
quantize the 7-bit MIDI
>volume data to the 4-bit 2600 volume setting. You
could also interpret
>channel/voice data and convert that into direct
distortion settings in the
>bytestream.
All that preprocessing, if really necessary could be
done by the circuit plugged into the joystick port, too.
And this circuit is needed anyway, for the opto-
isolation.
>If you wanted to simplify things further, rather than
an expensive to design
>chip, you could have some kind of MIDI interface
software for the PC that
>performs the preprocessing in real-time before sending
the signal down the
>pipe.
Well, I have a PC, my brother still uses an Atari ST and
our friend with the studio equipment is running a MAC of
course...
>According to my rough calculations, at MIDI speed,
assuming that you are
>totally maxing out the MIDI bandwith just for the 2600,
you'd have 64 bytes
>per 60th of a second to process. I don't see how that
would ever happen in
>the real world, though, when controlling a device that
only has 2 sound
>channels.
Hm... everything sounds sooo doable. So why isn't any
MIDI stuff existing for the VCS so far? :-)
>The networking layer on the PCs could be peer-2-peer
and handle all the
>connection issues for the 2600.
Hehe... and I recently thought that creating a 2-Player
Roguelike game with 2 VCS connected via Joystick ports
is way over the top :-)
Greetings,
Manuel
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