Welcome and let me introduce some of my projects and ideas.
My prototype. I was too lazy to place descriptions over the pots and switches...
AVRSYN is a monophonic "virtual analog" synth based on an Atmel AT90S8535 microcontroller. My aim was to check if a simple micro can be used for sound synthesis purposes. And the result? The 8535 managed to do all the tasks: front panel switches and pots services, receiving and processing MIDI messages, and sound generating! The synthesis architecture is simple: two DCO's, a DCF, and a DCA. There is also an LFO and an AR/ASR envelope generator.
The schematic is here
The source code is here (all comments
translated to English by Laurie Biddulph and me)
The Intel hex code is here. NOTE: the
code has been updated for ATmega16 and now
supports MIDI channel selection.
Visit also the Laurie's
webpage where you will find many informations, eg. how to
order a PCB.
Daniel Kruszyna added some
interesting features to the AVRSYN.
Here is how Gergo Palatinszky, Arto
and Laurie Biddulph built their pieces:
It is an idea of another Atmel-based musical project. The
ATmega8 microcontroller acts as a "virtual analog drum"
synthesizer. The sound path consists of two sine wave oscillators
and a noise source. There are 3 simple envelope (decay-only)
generators: one for the sine waves' amplitudes, one for noise
amplitude and one for pitch bending. 6 parameters are controlled
by potentiometers: SINE1/2 MAIN TUNE, SINE2 DETUNE, SINE1/2 DECAY
TIME, SINE1/2 PITCH BENDING, NOISE DECAY TIME, NOISE LOWPASS
CUTOFF FREQUENCY.
I built a small PCB and developped the code. Nice sounds can be
produced, and I like the possibility of getting a variety of
sounds just by turning the knobs.
Some years ago I had an idea of building a polyphonic synth with each voice consisted of a triple DCO followed by an analog Moog ladder VCF and a VCA. The triple DCO was an AT90S1200 (now obsolete). Its main task was to generate three sawtooth waveforms. The AT90S1200 was digitally controlled from a "master CPU" through an 8 bit bus, and generated 8 analog voltages (external 8 bit DAC + 4051 + sample&hold). Three of the voltages were sawtooth waves, the remaining five were control voltages.
The schematic you'll find here
The source code is here
Note: instead of trying to understand the whole source code, better concentrate on the triple DCO part (interrupt routine "INT_EXT0"). There is a mix of Polish and English comments in the code; nevertheless I hope you'll be able to understand how it works!
me
my wife in the Synthesizer Museum in
Klagenfurt/Austria
our son, a future musician
me at the Vienna City Marathon
my workshop
Last update: Nov 1st 2008
