LedBanner Multicast Receiver

A small C/SDL3 application that visualizes an 80x8 RGB565 LED banner from UDP multicast frames. Works when connected to the RevSpace WiFi.

What it does

• Opens an SDL3 window representing an 80x8 LED matrix (scaled for visibility).
• Listens on a multicast group for raw frames:
  • Default: 239.0.0.1:1565
  • Format: 80x8 pixels, RGB565, 2 bytes per pixel, 1280 bytes per frame.
• For each valid frame:
  • Decodes RGB565 to RGB.
  • Renders the pixels.
  • Logs simple stats (bytes, FPS, kB/s).

Code structure

• config.h
  • Dimensions, multicast defaults, AppConfig, DEFAULT_APPCONFIG.
• display.h / display.c
  • SDL init and draw_pixels_from_buffer(...).
• events.h / events.c
  • handle_sdl_events(...) (QUIT / ESC).
• multicast.h / multicast.c
  • setup_multicast_socket(...) for joining the multicast group.
• stats.h / stats.c
  • StatsState, logging of FPS / kB/s.
• main.c
  • Wires everything together:
    • init config + SDL
    • init multicast
    • event + receive + render loop
    • cleanup.

Build

Requires:

• C compiler (POSIX-like environment).
• SDL3 development files.
• pkg-config (recommended).

Build and clean:

make
make clean

Resulting binary: led80x8.

Run

./led80x8

• Expects 1280-byte RGB565 frames on the configured multicast address.
• Close window or press ESC to exit.

Local multicast test sender

• gol_sender.c is a small demo sender that generates a Conway's Game of Life animation on an 80x8 grid.
• It packs the grid into RGB565 frames (monochrome-style) and sends them via UDP to the same multicast address/port as the receiver.
• Useful for testing the receiver without needing the real LedBanner infrastructure.

./gol_sender

Disclaimer

This repo contains code written with the help of AI tools (Roo Code running an AI's from openrouter.ai), plus a fair amount of human stubbornness, debugging and cleanup.

• Some of it is smart, some of it is cursed. Treat every line as untrusted until proven otherwise.
• No guarantees about correctness, security, performance, or not accidentally summoning undefined behavior demons.
• I've put effort into shaping this into something usable, but you're still expected to read, test, break, and audit the code yourself—especially before using it in anything serious, exposed, or questionable.
• Some snippets may resemble third-party material. Make sure you respect licenses and applicable laws.

Short version: enjoy, hack responsibly, and if it breaks, you get to keep all the pieces.