There are a few things that will need to be addressed when connecting a midi
system to the GBA...
The first issue I see is the voltage difference - midi is a 5V interface
whereas the GBA comm system is 3V. While this isn't necessarily a problem
(as the nocash xboot cable works fine), it could potentially hurt the GBA's
comm system.
As far as whether the communications should be handled in software or
hardware, the only difference is what kind of a challenge the implementation
is. An external hardware system that buffers and retransmits data is
relatively simple to create, and much less of a pain to code for. It is also
possible to do the communicaitions on the gba itself. When in general
purpose comms mode, the GBA can be instructed to interrupt when SI
transitions from high to low, which will detect the beginning of an incoming
UART transmission. After that, at 31250bps, the gba has approximately 537
cycles per bit to deal with incoming data, so many means of collecting the
data (timer interrupts, or just wait loops) could be used.

In my opinion it doesn't really make much difference whether the
transmission and receiving is done in hardware or software... hardware has
the potential to be a bit more stable, but software won't require as much
external work.
-Stephen

----- Original Message -----
From: "douglas edric stanley" <destanley@...>
To: <gbadev@yahoogroups.com>
Sent: Tuesday, March 29, 2005 8:59 AM
Subject: [gbadev] MIDI->GBA interface




I'm trying to get MIDI into the GBA through the
serial interface. I've done lots of experimenting
with this serial port (cf.
http://hypermedia.loeil.org/playmobile/user/douglas/)
but getting MIDI in looks like it's going to be a
little uncomfortable. Has anyone already done
this? (I already know of all the GBC MIDI
projects -- pushpin & firestarter -- I'm
interested in a GBA-specific solution).

The main problem is that MIDI working at 31250
baud whereas the GBA supports only 9600, 38400,
57600, and 115200.

I was thinking of using the serial port in
General-Purpose mode, and trying to figure out
all the timing. This is cleaner than building a
PIC-based MIDI->UART converter, but I don't
really have any experience with General-Purpose
so I wanted to get someone's (anyone's?) opinion
on this matter before getting my hands dirty.
--
/*

// Douglas Edric Stanley
<destanley@...>

// Artiste
http://www.abstractmachine.net

// Professeur d'Arts numeriques, L'école supérieure d'art d'Aix-en-provence
http://www.ecole-art-aix.fr/hypermedia/

// Chercheur, Laboratoire Esthétique de l'interactivité, Université de Paris
8
http://www.ciren.org

*/






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