[sdiy] MIDI for dummies

[Bob Weigel]

I think I put a few links on my site somewhere. 

But concisely

1) MIDI = musical instrument digital interface

2) http://www.scit.wlv.ac.uk/~c9725449/whatismidi.html is a brief history

3) MIDI is a serial data stream travelling as a current loop.  The 
middle pin of a 5 pin din connector is ground but is only used as a 
single ended shield usually.  It's not usually needed except with very 
long runs or in very noisy environments I would think.  As in EM pulses 
etc. :-) But anyway the two wires next to it...the 'out' port has one 
wire hooked from a 220ohm resistance to 5V.  The other to a buffer or 
inverter chip that is driven by a cpu or uart or whatever.  On the other 
end of the wire, the "IN" port's wores are hooked across a photo diode 
of an opto isolator after a 220ohm resistor also usually. A 'thru' port 
may also be set up to, if selected to do so if such an option exists in 
software which sometimes it does, send the in data on to the next device 
also.

4) the code itself consists of a "Status byte" which identifies the type 
of message and channel that is to follow.  First bit is high if it's 
status and next three are a code for the type of message (eg. note on, 
or bender) Next four are MIDI channel 1 - 16 represented by hex 0 - F

The following byte will have a zero at the beginning to signify it's 
data.  If it's note on for instance it is a two byte message and the 
first is the note number, second is velocity.  7 bits of data for each.

Messages that start with OxF are system messages.  F8 is clock as I 
recall,  F7 is a system exclusive message which can be of any length.  
F0 signifies it's termination.  THese messages usually begin w/ 
manufacturer's codes and so on then might contain patch information or 
some parameter change information that isn't provided for in the other 
types of messages.

There's a good start. -Bob

Dirk Vanden Berghe wrote:

> Hi,
> I'm looking for some kind of tutorial for MIDI. I'm a real dummy :-)
> where can I start?
> thx
> Dirk
>
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