FW: [sdiy] Digitally controlled VCO core

[Anderson, Robert O]

BBD?  soap?  bubbles?  music?

>The frequency of the oscillator is determined only by the uC timer.

This really sounds like the CEM3396 scheme.  Take a look at:
http://www.synthtech.com/cem/c3396pdf.pdf
It talks about how to compensate for the amplitude dependence on frequency.

I link the cap more intimately with the uC in a feedback loop so that,
rather than crystal controlled frequency, the charging cap determines the
frequency and phase.

> waveforms (rectangle, pulse, square and maybe PWM sine and  triangle for
LFO) directly from the uC pins.

Quite a bit of flexibility for not much circuit and it's still a little
analog.

Bob A.