Documentation of building a polyphonic MIDI synth & generative sequencer using the STM32F401 & STM32F746 discovery boards. If you want to build your own synth, sign up for a workshop @ http://workshop.thi.ng 

stm32f4/f7

Created during 3-day ACT Festival workshop, demo of 3-track sequencer (no MIDI) w/ interactive scale-locked transpose control

stm32f401 - polysynth + 3-track sequencer (ACT workshop)

Created during 3-day ACT Festival workshop, demo of 2-track sequencer (no MIDI) w/ interactive scale-locked transpose control. Sine oscillators only for more minimalism

Sign up for more workshops: http://workshop.thi.ng

stm32f401 - 2-track sequencer (sines only, ACT workshop)

2 track seq (each w/ 2 saw osc), high pass filter. Live modulation via via Korg Nanokontrol2

stm32f401 - saw - highpass - nanokontrol

Spontaneous improv with 2 STM dev boards and Korg Nanokontrol

stm32f401 - 2x synth - 4track improv

Demonstration of artificial bit saturation & overdrive (14bits, 12bits, 10bits, 8bits)

stm32f401 - synth - saturation & overdrive

Hardsaw => Hardfloor, a little homage to: https://www.youtube.com/watch?v=Un4CeV_l3pI

stm32f401 - synth - hardsaw (12bit saturation)

Testing new stack-based synth implementation. Each voice consists of 11 operator nodes (env, osc1, osc2, sum, LP filter, delay1, HP filter, delay2, delay3, madd, panning)

stm32f7 - synth - dsp node stack

Testing new stack-based synth implementation. Each voice uses 15 operator nodes, in order: env, lfo1 (pitch), lfo2 (vol), osc1, osc2, sum, foldback, mult, LP filter, delay1, HP filter, delay2, delay3, madd, panning

stm32f7 - synth- foldback distortion

2 detuned sawtooth oscillators, 3 stacked delays & tweaked formant filter implementation based on: http://www.musicdsp.org/showArchiveComment.php?ArchiveID=110 - uses all vowels (AEIOU)

Alas only monophonic (currently too slow). Also a bit too ringing in places...

Interested? Sign up for next ARM synth workshop @ http://workshop.thi.ng/

stm32f7 - synth- formant filters

New Formant synthesis oscillator type + Lowpass Filter (w/ random cutoff) + interactive delay feedback control

stm32f7 - synth - formant synthesis

4 voices + 1 formant osc + high pass filter (w/ random cutoff) + simplex noise based automation of delay feedback 

stm32f7 - synth - formant synthesis (drones)

2 detuned bandwidth limited square osc + LFO controlled PWM. PolyBLEP phase shaping is used to limit BW and reduce aliasing (though not 100% avoiding it). Code adapted from here: http://research.spa.aalto.fi/publications/papers/smc2010-phaseshaping/

stm32f7 - synth - polyblep + pwm

probabilistic sequencer + formant osc + sawsin subosc (w/ synced impulse freq mod) + initial aux bus implementation (still all mono)

stm32f7 synth - formant + subosc + aux

2 tracks (8 voices) of initial stab at Karplus-Strong (https://en.wikipedia.org/wiki/Karplus%E2%80%93Strong_string_synthesis) with randomized impulse length & filter coefficient + LFO-based stereo panning + delay. Second melody plays a 5th and has LPF linked to note to create more of a nylon string character

stm32f7 - synth - karplus-strong (2 track)

Experimental spiral oscillator (x 2, slightly detuned) + fixed LPF @ 11.8kHz. Oscillator takes y-value of 2d spiral equation to produce waveform (with PolyBLEP to smooth). No filter modulation. LFO is only used to modulate number of spiral turns/twists (0.5 - 3.5)

sin(lfo * phase) * phase / TWO_PI

stm32f7 - synth - spiral

Another bunch of variations (using different LFO settings) of the test bass step sequencer. More info: https://hackaday.io/project/9374-stm32f4f7-synstack

synstack - forth - bass seq variations

Some dirty easter beats made w/ Ableton + fat bassline and other synths brought in (sampled) from STM32F7, courtesy of http://thi.ng/synstack

20160325 sketch (STM32F746 + Ableton)

Best enjoyed with headphones! Recorded live set in hotel after last minute tech issues during my lecture. Turned out the Korg nanoKontrol lost its configuration earlier - such a shame, was looking forward to hear it on big speakers! :)

Synth is running on a £35 STM32F746-DISCO board and also implements a 2-track 8-step sequencer w/ interactive controls for osc waveform, filter, env, delay, LFO and global transpose all via Korg nanoKontrol... Activated notes are randomly picked from a fixed scale (only once, not random at every invocation)

STM32F7 live recording (Resonate)

http://thi.ng/synstack demo running on ARM Cortex-M7 / STM32F746-DISCO, full source code http://github.com/thi-ng/ws-ldn-12 (ex07)

stm32f7 - synstack - 3 osc + fb + sdramdelay (WS-LDN-12)

Another workshop example (ex06), more info here: http://thi.ng/ws-ldn-12

stm32f4/f7

forthcharlie