103 Music for ASICs
103 : Music for ASICs
- Author: d5smith
- Description: Autonomous generative ambient music chip using LFSR composition, scale quantization, and DDS synthesis
- GitHub repository
- Open in 3D viewer
- Clock: 25000000 Hz
How it works
Music for ASICs is an autonomous generative ambient music chip. It creates musical structure with pseudo-random LFSRs, maps the resulting note values onto musical scales, and renders the result with two direct digital synthesis voices.
The audio pipeline is:
LFSR composition engine -> scale quantizer -> DDS sound engine -> DAC/PWM output
Three maximal-length LFSRs, 5-bit, 7-bit, and 12-bit, produce deterministic pseudo-random sequences with co-prime periods. The short LFSRs shape note choice and melodic variation, while the 12-bit LFSR adds slower movement. A combinational quantizer maps raw note values onto pentatonic, minor 7th, blues, or fallback tuning tables.
The sound engine contains two DDS oscillators: a bass voice and a melody voice. Each voice supports square, triangle, and sawtooth waveforms. The voices are envelope-smoothed, mixed digitally, and exposed as both a 4-bit parallel DAC output and a single-pin PWM audio output.
How to test
- Apply the Tiny Tapeout 25 MHz clock.
- Hold
rst_nlow, then release it. - Music starts automatically after reset.
- Connect an R-2R ladder to
uo_out[3:0]for 4-bit DAC audio, or low-pass filteruio_out[0]for PWM audio. - Use
ui_in[1:0]to select scale:00pentatonic,01minor 7th,10blues,11fallback. - Use
ui_in[3:2]to select tempo:00slow,01medium,10fast,11very fast. - Use
ui_in[5:4]to select the bass waveform:00/11square,01triangle,10sawtooth. - Use
ui_in[7:6]to select the melody waveform:00/11square,01triangle,10sawtooth. - Optional: connect LEDs to
uo_out[7:4]to view debug activity.
External hardware
- 4-bit R-2R DAC ladder on
uo_out[3:0], for example using 10k and 20k resistors. - Or an RC low-pass filter on
uio_out[0]before a high-impedance audio input or amplifier. - Optional LEDs on
uo_out[7:4]for sample tick, voice-active, and LFSR debug signals.
Do not connect low-impedance headphones directly to a GPIO pin. Use an amplifier or a suitable high-impedance input stage.
IO
| # | Input | Output | Bidirectional |
|---|---|---|---|
| 0 | scale_sel[0] | DAC bit 0 (LSB) | PWM audio out |
| 1 | scale_sel[1] | DAC bit 1 | |
| 2 | tempo_sel[0] | DAC bit 2 | |
| 3 | tempo_sel[1] | DAC bit 3 (MSB) | |
| 4 | wave_bass[0] | Debug: sample tick | |
| 5 | wave_bass[1] | Debug: bass active | |
| 6 | wave_melody[0] | Debug: melody active | |
| 7 | wave_melody[1] | Debug: LFSR-12 MSB |