This cart uses the built-in analog components of a single PIC microcontroller (op-amps, comparators etc) to implement 3 analog channels, each with different filter characteristics.
- Tone: Dual rectangular waves with low-pass filter and switchable resonance (bridged-t filter)
- Click: Single pulse with extra-resonant bass filter for 808-like percussion (twin-t filter)
- Noise: Analog noise generator with higher frequencies, medium resonance bandpass filter (bridged-t filter)
The noise channel may also play two detuned, XORed square waves.
In this video, all filters are on, resonance is set to maximum and the tone channel's cutoff is controlled via buttons.
My goal was to use only the PIC and the usual bunch of passive components (Rs and Cs) to do as much analog as possible. The PIC acts as a hybrid soundchip here, somewhat similar to a SID, with a very specific character.
The whole circuit fits into a nanoloop one-like flat cart. Sound plays through the Game Boy's headphone output.
Last edited by oliver (May 13, 2016 3:26 pm)