On Thursday 08 January 2004 00:27, you wrote:
>     Actually, Koen's proposal looked like straight PWM; I'm sure the
>     PICLIST archives contain numerous examples of PWM sine-wave
>     generation using a quarter-period lookup table.  Lancaster's
>     "magic sine waves" are different in that they cancel harmonics.

There is nothing magic about it, but its not PWM either (at least, I use only
full on/full off).
The thing that makes it look like a sine wave is the integrating amplifier.
See the attached PNG:
Green the sine I want to achieve, blue the PIC output and red the integrand of
the PIC output.
In binary the PIC output is 11110110 10010000 00001001 01101111,
which is 0xF6, 0xF6 flipped&inverted, 0xF6 inverted, 0xF6 flipped.
So you need a quarter-period lookup table of 1 byte. That's not a large
table...

I hope this makes something clear :o)

Koen

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads