On 16/11/2006, at 23.53, Chuckk Hubbard wrote:
My plan was to send PWM from my serial port, then use a low pass
filter to obtain DC to
control a Moog synthesizer's pitch.
I don't quite understand how a PWM'ed signal put through a low pass
filter can give a voltage controlling signal. Care to explain? I'm
not even sure how to make the PWM signal at all - will it only be
using one pin? I might be daft.
I thought the easiest way to obtain such a signal from a serial port,
was to make a D/A converter fx with a transistor construction
(couldn't just find a diagram on the internet), such that each bit
sent to the port would translate to a DC signal. I know the precision
of the values might be sloppy and that there will only be 2^{# of
data pins on the port} different control values to mess with - but
still?
I read about it in Delton T. Horns Music Synthesizers: A Manual of
Design and Construction, if i recall correct, where the author
suggested to use a S/H in connection with such a converter to save
CPU power (when one wanted to keep a given CV for a period of time
(faster then the port)).
Christian Klippel, however, has kindly offered to create a USB->CV
adaptor for me, something others have suggested but which has
proven too confusing for me.
That's very nice. I'd really love to make such a lil' donkey myself.
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