[sdiy] avrsyn code

[Daniel Kruszyna]

dougall <dougalli at gmail.com> wrote:
> Velocity should probably control the sustain level of the evenlope but in 
> AVR-synth I'd say just the final amplitude. You could use one of the spare 
> switches to optionally route it to the filter cutoff as well.
> 
> It would be nice to improve the filter a bit. It might be feasible to 
> implement a 12dB SVF and add a switch to choose HP or LP. There is example 
> code on www.musicdsp.com <http://www.musicdsp.com> for 12dB SVF and there 
> are some good papers on avrfreak.net <http://avrfreak.net> on doing fixed 
> point dsp on avr's.

I will check out this reference. I still need to read up some more on
digital filters. I got the formula for the current high pass filter from
a suggestion someone made on this list.

I tried multiplying in velocity to the final dca level. It works, but I
think I'm running into glitches from the lookup tables again. A few more
tests...

> I don't think there are any spare knobs for the resonance control but 
> perhaps you could use a spare switch to select what function a certain knob 
> is controlling. When the avr reads the knob values, it could check a switch 
> value then load the knob value into the correct location based on the switch 
> setting.

I had this idea as well. Maybe use two switches as a "page select". The
code would have to keep an extra copy of all switch and pot settings
and only update the real parameters when an input changes. Another option
is to MIDIfy all of the parameters. I might do this in preparation for
another project I'm working on.

-- Daniel