[sdiy] question re: microcontrol of synths...

[Byron G. Jacquot]

>Does anyone know of a way to use an older micro (say a
>commodore 64 or TI99...something with a BASIC
>programming interface) to send CV/Gate to synths...I
>have seen it done (in fact there is a gentleman on
>musicsynthesizers.com with a picture of it happening)
>but can't find any information about HOW...want
>something less 'musical' than midi, but can't really
>afford the time/space/expense of a wall of analog
>sequencers/clock/boolean logic/sequential switches
>right now...

The Commodore 64 makes an interesting platform for some musical
experimenting.  It's got the SID synth chip that can be used for some decent
analog tones, and it also had an "experimenters port" on the back...I think
it was a parallel port, but it's been so long that I dont exactly recall.
Radio Shack used to sell a protoboard that would tie right to that port.
You could build a simple DAC with a latch and some resistors, if you don't
care too much about intonation.

In basic, you'll want to use the "peek" and "poke" statements, which allow
you to read & write the hardware registers.  You can poke values into SID
fron the command line.

The trick is in knowing the memory locations to peek and poke from, so
you'll need to find the memory map somewhere...the TI99 is probably similar
in this regard, but I don't know the specifics of the port details.

I had a book about programming the C64 which went into details about all of
this stuff, including a chapter or two about using SID.  It would be a good
resource to get started with.  It was a fairly common book, and if I reacll,
it had a grey cover and a spiral binding...

Byron Jacquot