Open Grid Controller

Open Grid Controller is an open-source 8x16 grid controller for music production, live performance, sound experiments, and interactive installations. It uses an RP2040-Zero as the main controller, appears over USB as a monome grid-compatible device, and bridges 128 key inputs plus per-key LED brightness control to two 8x8 I2C keypad/LED boards.

The project includes ready-to-build PlatformIO firmware, STEP files for the 3D-printed enclosure, and reference photos for assembly. You can use it as a complete DIY controller, or adapt it into your own sequencer, visual controller, media installation input panel, or monome-compatible hardware project.

Features

• 8x16 matrix layout with 128 independently readable keys.
• Per-key LED brightness control with 16 levels, from 0 to 15.
• USB serial protocol compatible with the core monome grid input and LED control workflow.
• Based on RP2040-Zero, Arduino Core, and Adafruit TinyUSB.
• Two 8x8 FREEPOET-Keypad I2C boards combine into a full 16-column grid.
• Supports key debouncing, hot-plug detection, full LED sync, and incremental LED refresh.
• Includes 3D-printable enclosure files for replication and customization.

Product Photos

The front panel uses a classic 16-column, 8-row grid layout, suitable for step sequencing, clip launching, parameter mapping, and mode switching.

The enclosure has a low-profile desktop form factor with a side USB port, making it comfortable to keep beside a synthesizer, controller, or computer.

Open Grid can be used alongside other hardware controllers. The photo above shows it working with Shield Pro on the same desktop, forming a more complete live performance control setup.

Hardware

Bill of Materials

FREEPOET OpenGrid kit: https://github.com/FREEPOET-OFFICIAL/FREEPOET_Keypad

• RP2040-Zero main controller board.
• Two 8x8 FREEPOET_Keypad key/LED boards.
• Eight 4x4 silicone pads.

Parts to prepare separately:

• 3D-printed top cover and bottom shell.
• 4 wires.
• 24pcs M2*6 mm self-tapping screws.
• 8pcs M2*10 mm self-tapping screws.
• 6pcs M3*8 mm self-tapping screws.

The firmware uses Pico I2C0 by default:

• SDA: GPIO 4
• SCL: GPIO 5
• I2C speed: 100 kHz

Select the address jumpers as shown by the red circles in the image below:

• Board 1: solder the address bit 0 jumper.
• Board 2: solder the address bit 1 jumper.

Repository Structure

.
├── enclosure/              # 3D enclosure STEP files
│   ├── OpenGrid-Bot.step
│   └── OpenGrid-Top.step
├── pics/                   # README and assembly reference images
└── sw/                     # PlatformIO firmware project
    ├── platformio.ini
    └── src/

Firmware Build and Upload

The firmware is built with PlatformIO. The target board is Raspberry Pi Pico.

1. Install VS Code and the PlatformIO extension.
2. Open the sw directory in this repository.
3. Connect the RP2040-Zero.
4. Build and upload the firmware:

cd sw
pio run -t upload

Software Compatibility

On the USB side, Open Grid uses a monome-style serial device descriptor and reports OpenGrid as the device ID. The firmware implements common commands such as grid size query, device ID handling, key event reporting, and single-pixel, region, and full-grid LED control. It is intended to work with music software, scripts, or custom toolchains that support monome grid devices.

The current firmware focuses on providing a stable 8x16 grid interaction layer. If your software depends on more complete monome protocol behavior, test it against your target application and extend sw/src/MonomeSerialDevice.cpp as needed.

Enclosure and Assembly

The enclosure STEP files are in enclosure/:

• OpenGrid-Top.step: top cover.
• OpenGrid-Bot.step: bottom shell.

Use Cases

• Sequencer and rhythm programming controller.
• Grid input panel for Max/MSP, norns, SuperCollider, Pure Data, and similar creative environments.
• Lighting, visual, and media installation control surface.
• monome protocol learning and open-source hardware experimentation.
• Hardware foundation for custom MIDI, OSC, or USB controllers.