Sequencer microprocessors

[Stewart Pye]

Hi There,

An 8051/8031 would do the job. You could use a keypad interrupt enabling
you to change from write to play mode while running. The built in uart will
handle midi. You shouldn't need too much discrete logic. A 4 input and on
the keypad matrix outputs could trigger an external interrupt. So you can
scan a heap of switches without using too much port space you can use a
74138 (3 to 8 line decoder) for the outputs to the keypad, permitting a 4
by 8 switch matrix using only 7 bits of the 8255 port C. An 8255 PIA would
be useful for the keypad and the led's.Hey, I might do this myself !!

Of course you could also use a Motorola or PIC microcontroller, I'd use an
8031 because thats what I know and I've found the instruction set to be
flexible and relatively easy to understand.  

Do you want to have midi control of the sound triggering or sound tone. The
triggering would be pretty easy, The tone/pitch would be harder. You'd need
a DtoA for a cv and then have the sound source parameters voltage
controllable.


Regards,

Stewart Pye


At 13:11 12/01/99 -0600, you wrote:
>"Budweiser [FTS]" wrote:
>> 
>> I am really interested in the idea of a cloning the 909 drum machine,
>> now that i have enough information about the circuits (especially the
>> the sample playback circuits for the hihats/cymbals).
>> 
>> What sort of processor would be best for such a design? Keeping in
>> mind I want to add more recent features found on modern instruments
>> like realtime midi control of the sounds, and leaving the sequencer
>> running while changing from play to write mode (like the 606).....
>> 
>WEll, a PIC would be good enough just to control the interface and
>memory. You would still prlly have to go down and dirty and use discrete
>logic otherwise you will be debugging forever with a play/write
>simultaneous mode.
>Rob
>