Custom music instruments here at Hackaday range from wacky to poignant. OpnBeat by [Hiro Akihabara] focuses on something different: simplicity.
There are few buttons, the design and code are optimized to be straightforward and easy to modify, and the interface is slick. Eight musical keys complement three interface keys and a knob. An Arduino Nano powers the main brains of the system but the music generation comes from eight Nuvoton ISD1700s controlled over SPI by the Nano. The beautifully laid-out PCB is 110mm by 180mm (4.33″ by 7″), so cases can easily be printed on smaller FDM printers. All the switches are Cherry MX switches for the beautiful tactile feedback.
The code, PCB, and 3D case files are all available on GitHub. We love the thought that went into the design and the focus on making it easy to recreate. It might be quite as cute and simplified as this twelve-button musical macro pad, but the two together could make quite the band.
ISD15100 would give you 48 khz audio.
ISD1700 is a strange beast. It stores each sample in an EEPROM cell as an analog charge instead of using digital storage with ADCs/DACs and compression. It hails back to the late ’80s and its siblings were popular in greeting cards and toys as they were extremely cheap and low power yet had higher fidelity than the LPC mask rom chips that came before.
AI accelerator companies are just now releasing chips storing analog values in flash for in-memory compute, but they’re building on technology that was being sold by Hallmark three decades ago.
This looks really interesting, will there be any MIDI support?
here’s an unreated but related thread that might hep as a jumping off point for adding MIDI support via the Nano:
https://www.electro-tech-online.com/threads/midi-input-circuit-to-trigger-analog-synth-voices.158551/
It has no MIDI output. It only has mixed LINE OUT and headphone out.