MicroTone Synthesizer 6502
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Built a 4-note microtonal synthesizer using the vintage KIM-1 microprocessor and 6502 assembly.
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Implemented a phase-accumulator Direct Digital Synthesis (DDS) engine with PWM audio output.
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Stored frequency control words for microtonal tuning (e.g., 31-TET) and used a sine wave lookup table for waveform generation.
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Interfaced with GPIO via 6522 VIA; used the onboard keypad for real-time note selection.
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Optimized timing-critical IRQ routines and zero-page memory access for cycle-accurate waveform playback.
The above code was written and assembled using ASM80. The lst and hex code is available.