USB Webcam Ringlight

A SAMD21/WS2812 based, low-cost and low-difficulty USB webcam ringlight. Designed for a logitech streamcam (though there is no reason not to create other attachments) and controlled via USB/HID because, why not.

Parts

• 3d-printed support
• seed studio xiao-m0
• 24-led WS2812 ring.

Getting Started

The ringlight firmware runs on a seed xiao board with WS2812 LEDs connected to pin 10, and can be installed via the uf2 bootloader. Both the device firmware and control utility can be downloaded from the releases page, while the control utility can be installed via cargo install rlctl if preferred.

Setup

First you need to connect a set of WS2812 LEDs to the xiao, linking GND->GND, VCC->5V and Pin 10 -> DI (Data In). You can then load the firmware on the device by:

• Download the latest rlfw.uf2 file from the releases page
• Connect the xiao board to your computer via USB
  • This should connect as a disk drive
  • If this does not occur you may need to short the GND/RST pads on the back of the board twice in quick succession
• Copy the rlfw.uf2 firmware file onto the drive

Usage

• rlctl set-brightness BRIGHTNESS to set brightness
• rlctl set-rgb R G B to set RGB colour output
• rlctl help to show help message / options

Note that values must be between 0-255 (or 0x00-0xff).

Linux / udev rules

On linux you will need a udev rule to provide your user with permission to access the device. If your account is a member of the plugdev group this may look like: /etc/udev/40-ringlight.rules:

SUBSYSTEM=="usb", ATTR{idVendor}=="1209", ATTR{idProduct}=="fff1", MODE="0660", GROUP="plugdev"

Development

• rlfw contains the SAMD21 ringlight firmware
• rlclt contains a ringlight control utility

Dependencies

• rust with target thumbv6m-none-eabi (via rustup target add thumbv6m-none-eabi)
• libusb via sudo apt install libusb-dev libusb-1.0, brew install libusb, or vcpkg install libsusb (and maybe a LIBUSB_DIR setting on windows)

Compiling / Flashing Firmware

Note that memory.x must be edited to remove the flash offset if your xiao-m0 does not currently have the bootloader loaded.

Other options:

• cargo build --release to build the binary
• cargo flash --chip ATSAMD21G18A --speed 100 --release to flash via a connected debugger
• cargo hf2 --release --vid 0x2886 --pid 0x002f to load via the bootloader (YMMV)

Generating .uf2 compatible firmware files

.uf2 files can be loaded onto the board by dragging and dropping into the correct file system.

Dependencies:

• rustup component add llvm-tools-preview
• cargo install cargo-binutils u2fconv-rs for creating .uf2 bootloader files

Steps:

• cargo objcopy --bin rlfw --release -- -O binary rlfw.bin to output a release binary file
• uf2conv rlfw.bin --base 0x2000 --output rlfw.uf2 to generate a uf2 file