t-picoc3-device-midi2

midi2cpp | Device MIDI 2.0

LilyGO T-PicoC3 (RP2040 side)

Full-spec USB MIDI 2.0 device on the LilyGO T-PicoC3, RP2040 side. Headless single-file showcase of every MIDI 2.0 message category beyond MIDI 1.0. Pico SDK build, no Arduino IDE.

The board carries two MCUs sharing one USB-C jack via a physical orientation switch on the connector edge: the RP2040 in the canonical orientation, an ESP32-C3 in the flipped orientation. This recipe targets the RP2040 side; the C3 runs its own firmware. See t-picoc3.md for the full hardware reference.

USB identity

Field	Value
VID:PID	cafe:4079 (development-only)
Product	TPicoC3
Manufacturer	github.com/sauloverissimo

Build

Requires Pico SDK 2.x (with PICO_SDK_PATH exported), arm-none-eabi-gcc, CMake 3.14+.

cmake -B build         # first run fetches TinyUSB
cmake --build build -j

Pointing at a local TinyUSB checkout: cmake -B build -DPICO_TINYUSB_PATH=/path/to/tinyusb.

Flash

Hold BOOTSEL on the RP2040 side, plug USB-C in the canonical orientation, drag build/t-picoc3-device-midi2-showcase.uf2 to the mounted RPI-RP2 drive. Or picotool load build/t-picoc3-device-midi2-showcase.uf2 -fx.

If the host enumerates 303a:1001 instead of cafe:4079, the connector is in the flipped orientation (ESP32-C3 connected); flip 180° and replug.

Hardware

Pin	Use
USB-C	MIDI 2.0 device (shared with ESP32-C3 via orientation switch)
GP0 / GP1	UART TX/RX debug print @ 115200 8N1
GP25	Red LED, lit while USB is mounted
GP22	PWR_ON for ST7789V display + peripherals (left LOW, display off)

The default UART debug on GP0/GP1 collides with the ST7789V TFT_RST/TFT_DC lines. The recipe keeps PWR_ON low so the display bus stays idle and UART is safe. To use the display, disable UART stdio in CMakeLists.txt and route debug elsewhere.

Validation

lsusb | grep cafe:4079
amidi -l
PORT=$(aseqdump -l | grep -i TPicoC3 | awk '{print $1}' | tr -d ':')
timeout 30 aseqdump -p ${PORT}

Spec coverage

Full spec. The RP2040's 264 KB SRAM affords the complete UMP + MIDI-CI surface.

UMP MT	Spec	Notes
0x0 Utility	M2-104-UM §3	JR heartbeat 500 ms, Delta Clockstamp
0x4 MIDI 2.0 Channel Voice	M2-104-UM §7	32-bit CCs, Per-Note family, Note Attribute, RPN/NRPN, Relative RPN/NRPN
0x3 SysEx7	M2-104-UM §7.7	up to 6 bytes per packet, auto-fragmented
0xD Flex Data	M2-104-UM §10	Tempo, Time Sig, Key Sig, Metronome, Chord Name, Start/End of Clip
0xF UMP Stream	M2-104-UM §11	full Endpoint + FB Discovery

MIDI-CI: Discovery + Profiles (1 custom registered) + Property Exchange (3 properties: static, dynamic, subscribable) + Process Inquiry, all via the m2ci Appendix E convenience responder.

Showcase

Always on while mounted: JR heartbeat (500 ms), UMP Stream + MIDI-CI Discovery responders, 1 custom Profile, 3 PE properties, Process Inquiry replies. GP25 LED lit.

Per cycle (~22 s):

Scene	Content	MIDI 2.0 only because
A. Flex Data	Tempo (120 BPM), Time Sig (4/4), Key Sig (C), Metronome, Chord Name (Cmaj7), Start of Clip	MT 0xD + 0xF
B. Per-Note	Sustained C4 with Per-Note Pitch Bend (5 Hz vibrato), Registered Per-Note Controller #7, Assignable Per-Note Controller #74, Per-Note Management Reset	Per-Note family is MIDI 2.0 only
C. Resolution	Chromatic walk C5→G#5 with 16-bit velocity ramp, 32-bit CC #74 sweep, 32-bit Pitch Bend, 32-bit Poly Pressure, 32-bit Channel Pressure	MIDI 1.0 caps at 7/14-bit
D. Program + Bank	Program Change with bank MSB/LSB in a single UMP	MIDI 1.0 needs three messages
E. RPN/NRPN	RPN 0/0, NRPN, Relative RPN (+delta), Relative NRPN (-delta)	RPN/NRPN first-class + Relative
F. Note Attribute	Note On with attribute_type=0x03 (pitch_7_9), E4 +50 cents	Microtonal attribute
G. SysEx7	Universal SysEx Identity Reply, 12 bytes, auto-fragmented (Start + End)	MT 0x3
H. Delta Clockstamp	DCTPQ=480 + Delta Clockstamp=240 ticks	MT 0x0 utility
I. PE Notify	Broadcast OverlayRate change to subscribers (value increments per cycle)	Property Exchange
J. End of Clip	Sequencer End of Clip marker	MT 0xF status 0x21

Every scene logs to UART on GP0 @ 115200 8N1.

License

MIT, inherits parent midi2cpp LICENSE.