sparkle-fw16

sparkle-fw16 is an alternate firmware for the Framework Laptop 16 LED Matrix Input Module, written in C using the RP2040 Pico SDK¹. Developed by vddCore, it was created as a leaner alternative to the official FrameworkComputer/inputmodule-rs firmware, which the author found had "too many useless features" and was written in Rust, a language they disliked¹.

The firmware implements the custom Glitter Protocol over USB HID, providing device info reports, basic commands (reboot, sleep/wake, brightness, draw pixel/line), and full grid PWM and DC scale control¹. A companion reference driver/renderer is available at vddCore/Starlight.Framework¹.

Motivation

The author's stated reasons for creating an alternative firmware were¹:

1. The official firmware "has too many useless features"
2. It is written in Rust, which the author's "eyes just cannot stand"
3. It "handles display interaction in a weird way that breaks my brain"

Architecture

When Sparkle starts up, it initializes three interfaces¹:

1. USB CDC interface — for debugging purposes; all messages are logged here
2. USB HID interface — for control purposes; API requests are sent here
3. RP2040 Reset interface — for easy flashing; the modified Sparkle Picotool makes use of this

Glitter Protocol v1.0

The Glitter Protocol is how Sparkle communicates with the host over USB HID, exposing 4 HID reports¹:

Feature Report 0x01 — GLITTER_DEVICE_INFO

Returns current device information including sleep pin state, DIP switch state, INTB pin state, state flags, IS31FL3741A register values, global brightness, display dimensions (9×34 for the official module), and firmware version¹. This report only accepts GET_REPORT control transfers¹.

Feature Report 0x02 — GLITTER_BASIC_CMD

Executes user-accessible firmware subroutines. The first byte specifies the command ID; subsequent bytes are arguments. Padded to exactly 16 bytes¹.

Command ID	Command	Description
0x00	GLITTER_CMD_REBOOT	Reboots into BOOTSEL mode (0x00) or firmware (0x01)1
0x01	GLITTER_CMD_SLEEP	Enter (0x01) or exit (0x00) sleep mode1
0x02	GLITTER_CMD_WAKE_ON_COMMAND	Toggle wake-on-command mechanism (draw commands auto-wake)1
0x03	GLITTER_CMD_SET_SLEEP_TIMEOUT	Set sleep timeout in ms (0 = disable, -1 = ignore all sleep requests)1
0x04	GLITTER_CMD_SET_GLOBAL_BRIGHTNESS	Set global LED brightness multiplier1
0x05	GLITTER_CMD_DRAW_PIXEL	Set a single pixel (x, y, brightness)1
0x06	GLITTER_CMD_DRAW_LINE	Draw a line between two coordinate pairs1

Feature Report 0x03 — GLITTER_GRID_PWM_CNTL

Takes 306 bytes representing the entire pixel grid's brightness values (9×34 = 306 LEDs)¹. Ignored if wake-on-command is disabled¹.

Feature Report 0x04 — GLITTER_GRID_DC_SCALE_CNTL

Takes 306 bytes representing DC scale values for every pixel. These correspond to the IS31FL3741A LED controller's current scaling registers, as documented in the included IS31FL3741A datasheet¹.

Installation

Building

cmake . -B build/ -G ninja -DCMAKE_BUILD_TYPE=<build_type>
cd build/
ninja

Where <build_type> is Release, RelWithDebInfo, or Debug. Requires RP2040 Pico SDK with PICO_SDK_PATH and PICO_TOOLCHAIN_PATH environment variables set¹.

Flashing

1. Remove the input module(s) from the input deck
2. Switch to BOOTSEL mode by toggling DIP-switch pin 2 to ON
3. Place the module(s) back in the input deck — a mass storage device appears
4. Copy the .uf2 file to the mass storage device
5. The RP2040 flashes automatically; the file disappears when complete
6. Remove the module(s), toggle DIP-switch pin 2 to OFF, and replace¹

Technical Specifications

Specification	Details
Language	C (Pico SDK)1
Target	Framework Laptop 16 LED Matrix Input Module (RP2040)1
Protocol	Glitter Protocol v1.0 (USB HID)1
Display	9×34 LED grid (306 LEDs)1
LED controller	IS31FL3741A1
Interfaces	USB CDC (debug), USB HID (control), RP2040 Reset (flashing)1
License	GPL-3.01
Commits	311
GitHub Stars	81
Source	vddCore/sparkle-fw16 (GitHub)1

Companion Project

A reference implementation for a Sparkle-compatible driver and renderer is available at vddCore/Starlight.Framework¹.

Related Projects

Project	Description
sigroot FW LED Matrix Firmware	Arduino-based alternative firmware for the LED matrix
LED Matrix Controllers	Cross-firmware JS/TS library supporting sparkle-fw16
LED Matrix Vocab	Japanese vocabulary tool with firmware auto-detection
led-matrix-manager	Qt GUI for LED matrix management
fw16-led-matrixd	Cross-platform Rust daemon for the LED matrix

Footnotes

1. vddCore/sparkle-fw16 — GitHub (README, Glitter Protocol documentation, build instructions) ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶ ↩¹⁷ ↩¹⁸ ↩¹⁹ ↩²⁰ ↩²¹ ↩²² ↩²³ ↩²⁴ ↩²⁵ ↩²⁶ ↩²⁷ ↩²⁸ ↩²⁹ ↩³⁰ ↩³¹ ↩³² ↩³³