[sdiy] DIY digital VCOs?

[Antti Huovilainen]

On Fri, 16 Jan 2004, denshi wrote:

> my brother is without internet connection, but wanted
> me to ask if there are any simple designs for DIY
> digital VCOs, he was particularly interested in basic
> stamp, or a solution like that.  two octave range at
> least.  thanks all!

You could use a MCU to act as half of a DCO.
I once designed (but never built) an Atmel microcontroller based DCO. One
output pin provided the reset pulse and eight of them acted as an
el-cheapo resistor DAC that provided the current to oscillator core.
Basic stamp is not fast enough to do this, as frequency resolution is
directly related to the speed of the mcu.

I would NOT recommend using an MCU to directly provide sawtooth with a
DAC. It will alias badly and sound quite horrible.

Antti

Give a man a fire, and he'll be warm that day,
Set him alight and he'll be warm for the rest of his life