Automatic Optical Audio Switch (ESP32)

Automatic switching between two TOSLINK / SPDIF inputs to one output based on signal activity detection with an ESP32C3.

Features

• 2× optical input → 1× optical output
• Automatic source selection (A/B)
• Signal detection via frequency measurement
• Configurable thresholds and timing
• Anti-flicker logic
• ESPHome firmware
• Web UI and Home Assistant integration
• No SPDIF decoding or audio processing
• USB-C powered
• 3D-printed enclosure

Concept

Each optical input is converted into a digital pulse stream. The ESP32 measures the divided SPDIF clock frequency and switches the output to the active (playing) channel.

Note

The actual audio path is switched purely in hardware. The ESP32 only controls the selection logic and does not touch the audio data stream itself.

Build

• Assemble PCB according to the KiCad project
• Flash ESPHome/OTA firmware
• Use Web UI or Home Assistant for configuration
• Connect device to optical audio setup

Complete Project Notes

available on Hackaday.io: https://hackaday.io/project/204791-automatic-optical-audio-switch-esp32