[sdiy] Using MIDI internally in a polysynth

Ingo Debus debus at cityweb.de
Sat Sep 1 11:30:57 CEST 2007


Am 31.08.2007 um 19:56 schrieb Colin f:

> Roland used MIDI busses internally between the assigner CPU and the  
> voice
> boards in the JX10.
> The assigner CPU only had a single hardware UART, as did the 8051s  
> on the
> voice boards, so they used the rather inefficient setup of having the
> external MIDI in connected to the assigner CPU, the assigner's MIDI  
> out
> connected to both voice boards ins, and the external MIDI out fed  
> by one of
> the voice board serial outs.
> MIDI transmitted from the assigner CPU has to be forwarded to the  
> outside
> world by a voice board.

Ugh.

I once built an 8051-based unit with two MIDI inputs. One was a  
"software-receiver", using the Programmable Counter Array (wait for  
falling edge, then sample the input at the appropriate moments). It's  
somewhat crude but works well, even at 12 MHz clock frequency.  
There's an application note from Atmel decribing this technique. I  
even built a three-into-one merger with two "software- 
receivers" (running at 30 MHz though). It worked well too.

Ingo



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