The suutari20 is an 18-key modular macro keypad that uses 3.5mm audio jacks as its connection standard, keeping per-unit costs low by relying on commodity hardware instead of custom connectors.
Each 3.5mm jack supports up to three keys, including analog inputs like volume knobs and jog controllers. The brain is an RP2040 on a Raspberry Pi Pico, running QMK firmware. The case is 3D printed. That is the entire build complexity.
What makes this worth reading is the connector choice: audio jacks solve the modular input problem without proprietary parts. The GitHub repo from creator Squalius covers the full design, and the linked comparison to a 2022 macro pad where each key carries its own microcontroller shows exactly how far this design philosophy can scale in either direction.
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