[sdiy] Using MIDI internally in a polysynth

[John Speth]

> How easy/difficult is it to talk to multiple voices
> with a SPI connection?

Using non-bussed SPI is no problem.  It's just point
to point.

Muliple device bussed SPI is more complex.  For
multiple device bussed systems, if you're trying to do
one way communication, SPI is easy.  If you're trying
to go two way comm, then you need to look at protocol
to control when devices enable their outputs.

It sounds like you need multiple bussed one way SPI. 
You can use chip selects to enable which devices
should listen.  Or you can skip the chip selects and
add some addressing protocol in your messages (usually
called the transport layer of your interface, the MIDI
messages are the payload).  The chip selectt method
gives you the capability to send the same message to
all devices in the same instant.

Of course, as someone else replied, you're free to
make your own changes to MIDI since the network is
private and internal.

As usual, it's all tradeoffs.

JJS



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