What you see in the photo above is a hand-made 4-oscillator synthesizer with MIDI input, multi-mode filter as well as a handful of modulation options. It was developed by [Matt], an AVR accustomed electronics enthusiast who made an exception to his habits for this project. The core of the platform is a DIP packaged 32-bit Cortex-M0 ARM processor (LPC1114), stuffed with ‘hand’ written assembly code as well as compiled C functions. With a 50MHz clock speed, the microcontroller can output samples at 250kHz on the 12bit DAC while being powered by 3 AA batteries.
Reading [Matt]’s write-up, we find that the firmware he produced utilizes 4 oscillators (sawtooth or pulse shape) together with a low frequency oscillator (triangle, ramp, square, random shapes). It also includes a 2-pole state-variable filter and the capability to change the attack-release envelopes (among others). The system takes MIDI commands from a linked device. We embedded videos of his development in action after the break.
