teensy41-control-surface

midi2cpp | Device MIDI 2.0

Teensy 4.1 control surface

Hardware-driven USB MIDI 2.0 control surface on the Teensy 4.1. 4 pots send CC 32-bit, 4 momentary switches send NoteOn/NoteOff 32-bit, and any UMP received from the host is decoded and printed to Serial. Companion to teensy41-midi2.

Cores fork + USB names override. Built against the Teensy cores fork sauloverissimo/cores branch feature/usb-midi2-descriptors. Overlay teensy4/usb.c, teensy4/usb_desc.{c,h}, teensy4/usb_midi2.{c,h} onto your Teensyduino install. Manufacturer + Product strings come from src/usb_names_override.c via the cores' weak-alias hook (usb_names.h).

USB Type menu entries. The cores fork carries the USB MIDI 2.0 implementation, but the Arduino IDE Tools > USB Type menu entries live one level up in the Teensyduino install. Copy boards.local.txt into ~/.arduino15/packages/teensy/hardware/avr/<version>/ (Linux / macOS) or C:\Program Files (x86)\Arduino\hardware\teensy\avr\ (Windows, IDE 1.x), then restart the Arduino IDE. The snippet was contributed by h4yn0nnym0u5e via the PJRC forum thread #55239, post #368245, and covers Teensy 4.1, 4.0 and MicroMod.

USB identity

Field	Value
VID:PID	16C0:0485 (PJRC USB_TYPE = MIDI2 slot)
Manufacturer	midi2.diy (via src/usb_names_override.c)
Product	Teensy41 CS (via src/usb_names_override.c)
iSerial	per-board chip serial
Endpoint Name	Teensy41 CS
Product Instance ID	Teensy41-controlsurface-0001
FB 0	Control Surface (Bidirectional, Group 0, both protocols)

Hardware

Pin	Function	Wiring
A0, A1, A2, A3	4 pots → CC32	wiper to A0/A1/A2/A3, ends to 3V3 and GND. 10kΩ linear
D2, D3, D4, D5	4 switches → NoteOn/Off	one terminal to D2/D3/D4/D5, other to GND. INPUT_PULLUP, LOW = pressed
USB device port	USB MIDI 2.0 + Serial 115200

CC mapping (GM 2 conventions): CC1 Modulation, CC74 Brightness, CC71 Resonance, CC91 Reverb Send. Notes: C4, C#4, D4, D#4 (60..63).

Teensy 4.1 pinout: https://www.pjrc.com/store/teensy41.html.

Build

arduino-cli compile -b teensy:avr:teensy41:usb=midi2 .
arduino-cli upload  -b teensy:avr:teensy41:usb=midi2 -p <port> .

In the Arduino IDE: Tools > USB Type > MIDI2 before Upload. Requires Teensyduino 1.60+, the cores fork overlaid, and the midi2cpp Arduino library on the sketchbook (the midi2 core is bundled).

Hardware validated 2026-05-27 on Linux ALSA (/dev/snd/umpC*D0): all 4 pots emitting CC1/74/71/91 with 32-bit values, all 4 switches emitting NoteOn/Off on notes 60..63, JR Timestamp heartbeat at 500 ms, decoded natively as MIDI 2.0.

How it behaves

After enumeration the device announces UMP Stream identity (Endpoint Info, Endpoint Name, Product Instance ID, FB Info, FB Name) and starts a 500 ms JR Timestamp heartbeat. Main loop:

1. Pots: first-order EMA (v += (raw - v) / 8) + 32-LSB deadband (~0.8% of the 12-bit range). 12-bit ADC expanded to 32 bits by MSB replication.
2. Switches: millis-based 20 ms debounce. Press emits NoteOn velocity 0xC000, release emits NoteOff velocity 0x4000.
3. RX: midi2::Device typed callbacks decode NoteOn/Off, CC, PitchBend, ChannelPressure, Program, Per-Note PB, Tempo, Time Signature to Serial.

MIDI-CI is not configured here; see teensy41-midi2 for Discovery + Profile + Property Exchange.

What lives where

teensy41-control-surface/
├── README.md
├── board/
│   ├── hardware.png           assembled hardware (banner)
│   ├── pinout.png             Teensy 4.1 pinout
│   └── stack.jpg              top-down setup view
├── monitor/
│   ├── banner.png             page banner image
│   ├── monitor.png            Microsoft MIDI Services Console monitor
│   └── properties.png         Microsoft MIDI Services Console properties
├── teensy41-control-surface.ino     sketch entry (setup + loop)
└── src/
    ├── teensy41_control_surface.h   backend glue declarations
    ├── teensy41_control_surface.cpp backend glue implementation
    └── usb_names_override.c         Manufacturer + Product via weak-alias hook

Spec coverage

Area	Coverage
MIDI 2.0 Channel Voice (MT 0x4)	Note On/Off with 16-bit velocity (switches), 32-bit CC (pots)
UMP Stream (MT 0xF)	Endpoint Info, Device Identity, Endpoint Name, Product Instance Id, FB Info + Name (boot burst; cores fork answers GET_DESCRIPTOR GTB)
MIDI-CI (SysEx7)	Discovery, Profile Inquiry (GM 1), Property Exchange (DeviceInfo, ChannelList, ProgramList + built-in ResourceList), Process Inquiry
RX handling	NoteOn/Off, CC, Program Change printed to Serial

Not covered: SysEx8/MDS and Flex Data emission (control surface stays minimal: it is an input device, not a full-surface showcase). Profile GM 1 and the Process Inquiry MIDI report are registered.

License

MIT, inherits parent midi2cpp LICENSE.