[sdiy] "AVR synthesizer"

[Jaroslaw Ziembicki]

----- Original Message ----- 
From: "Rainer Buchty" <rainer at buchty.net>
To: "Jaroslaw Ziembicki" <aon.912230836 at aon.at>


> With y[i]=x[i]-x[i-1]+m*y[i-1] you would have the simplest digital
> high-pass filter, just in case there's still some space left in program
> memory.

Thanks, Rainer! That formula of the 1st order high pass seems to be
known for me...
But I don't like high pass filters very much, so I never thought of
implementing one.
What would be interesting is a 2nd order variable state filter - with
switchable "low pass", "band pass", "high pass", and "band stop"
outputs. No big problem with implementing - assuming an ATmega
is being used...
By the way - an implementation of such filter in an FPGA would cost
some 20K gates... Anyone is going to try?

Regards
Jarek