Piano Synthesizer & Loop Machine

Piano keys rendered on a VGA display with several keys highlighted in cyan — the piano rendered on a VGA display. active keys light up as you play them.

the goal was to build a musical instrument that converts a user input into an audio tone, modelled on a traditional piano. it has 13 unique tones mapped to 13 unique inputs.

input is captured from a PS/2 keyboard, which passes through a PS/2 controller into the DE1-SoC board. the piano logic runs on the board and drives two outputs at once: a VGA display for visual feedback, generated from ROM through a VGA adapter and a digital to analog converter, and a set of stereo speakers through the audio controller and audio codec.

the tones are synthesized additively. every active input, whether it is live PS/2 input or a stored input read back from memory, is summed, fed into a square wave generator, and the resulting square waves are summed together. that combined waveform is then scaled into a final wave and passed to the audio controller and codec for playback.

on top of live playing, the synthesizer records up to 10 seconds of user input. a recording button (O) writes the PS/2 input into RAM, and a playback button (P) reads the stored input back out of RAM into the DE1-SoC so it can be replayed at will. the capture lives in the board's on-chip memory, and the pipeline is designed to run with under 5 ms of audio latency inside the 50 MHz timing constraints.

in the future it could take an external MIDI keyboard controller in place of the PS/2 keyboard. the plan would be to use a microcontroller such as an arduino to receive MIDI input and convert it into a bitwise code or PS/2 signal that the FPGA can read.

The physical setup: DE1-SoC board, PS/2 keyboard, and stereo speakers on a desk — the full setup: DE1-SoC board, PS/2 keyboard, and a pair of stereo speakers.

System block diagram from PS/2 keyboard through the DE1-SoC to VGA and audio output — system block diagram. PS/2 input runs through the PS/2 controller and DE1-SoC out to the VGA display and the audio codec.

Audio path diagram: inputs summed, square-wave generated, combined, scaled to the final wave — the audio path. live and stored inputs are summed, run through a square wave generator, summed again, then scaled into the final wave.

Record and playback flow diagram showing input written to RAM and read back on playback — record and playback. the recording button writes PS/2 input into RAM, and the playback button reads it back into the DE1-SoC.

VerilogQuartus PrimeDE1-SoCPS/2VGAFPGA