mDS - NDS and NDS-Lite MIDI Adapter - Complete Build

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mDS - DS slot-2 MIDI cartridge - Completely Built w / Shell

mDS is a Nintendo DS / DS Lite slot-2 (GBA Game Pak) MIDI interface built on an RP2040. It bridges hardware MIDI into the DS over the slot-2 SRAM bus so a DS app can be a MIDI synth. The DS is the synth; the cart is the interface - see the sDS synth app, the baseline ROM that runs on it.

One firmware, two jobs: mDS speaks the mDS `"STDS"` protocol (MIDI clock + a MIDI event ring), so the same cart drives both the sDS synth *and* clock-sync apps (e.g. stutter-ds) with no changes.

Instructions:

• Place the sDS ROM on the SD card of your favorite R4 or SD DS cartridge.
• Plug the cart into the DS before you turn the DS on.

Currently compatible with:

• sDS synth app (General polyphonic synth - free.)
  
• Stutter-DS (Glitch sequencer.)
• PadMe-DS (Atmospheric groove generator.)
• Moody-DS (Virtual analog synth.)
• Break-DS (Coming soon.)
• MIDIO-DS (Coming soon.)

Specs

MCU RP2040 - dual Cortex-M0+ @ 133 MHz, 264 KB SRAM

Host interface - GBA slot-2 SRAM region `0x0A000000`, 4 KB window (12-bit address), serviced by a PIO state machine

MIDI IN - 31250 baud UART, opto-isolated (H11L1) from TRS-A

MIDI OUT - 31250 baud UART, 2×220 Ω to TRS-A

Indicator - onboard green LED (GPIO25): status + MIDI activity

Power - slot-2 3.3 V

Compatibility - DS / DS Lite only (DSi+ dropped slot-2)


Build your own: https://github.com/HobbyChop/mDS