AudioMultiRoom

DIY multiroom audio system using ESP32 microcontrollers. No WiFi router or central server required.

Connect your phone via Bluetooth to any ESP32 speaker — the others sync automatically via ESP-NOW mesh.

How It Works

  📱 Phone
      │ Bluetooth A2DP
      ▼
  ┌──────────┐
  │  ESP32   │─── ESP-NOW broadcast ──►  ┌──────────┐
  │ SERVER   │                           │  ESP32   │
  │  🔊      │─── ESP-NOW broadcast ──►  │ CLIENT   │
  └──────────┘                           │  🔊      │
       │                                 └──────────┘
       └──── ESP-NOW broadcast ──────►  ┌──────────┐
                                        │  ESP32   │
                                        │ CLIENT   │
                                        │  🔊      │
                                        └──────────┘

Each ESP32 acts as a standalone Bluetooth speaker. When a phone connects:

• That device becomes the SERVER and broadcasts audio via ESP-NOW
• All other ESP32s automatically become CLIENTs and play the same audio
• When you disconnect, everyone returns to discoverable mode

No configuration needed — roles are negotiated automatically at runtime.

Current Status

🚧 Work in Progress — Currently debugging the Bluetooth audio path. ESP-NOW mesh functionality is temporarily disabled while we stabilize the core BT → I2S pipeline.

What Works

• Bluetooth A2DP sink (phone → ESP32)
• I2S output to PCM5102 DAC
• Notification sounds (startup, connect, disconnect)
• Basic volume control

Known Issues

• EMI Interference: Crackling noise when moving speakers/ESP32/nearby objects. Likely caused by long I2S wires (~20cm) near the ESP32 antenna. See Hardware Tips.
• Volume too high: TPA3116 amp has high gain — even at software volume 1/127 it can be loud with small speakers. Hardware attenuation recommended.

Roadmap

• Fix EMI/interference issues
• Re-enable ESP-NOW mesh broadcasting
• SBC codec for compressed audio over ESP-NOW
• ESPectre presence detection integration
• Dynamic volume based on presence
• Home Assistant integration
• OTA updates

Hardware

Bill of Materials (per speaker unit)

Component	Model	Cost
Microcontroller	ESP32 DevKit V1	~€5
DAC	PCM5102 I2S module	~€3
Amplifier	TPA3116 Class D 2x50W	~€10
Power Supply	12V DC adapter	~€10
Total		~€28

Wiring Diagram

┌─────────────────┐      ┌─────────────────┐      ┌─────────────────┐
│     ESP32       │      │    PCM5102      │      │    TPA3116      │
│                 │      │     (DAC)       │      │     (AMP)       │
│  GPIO26 (BCK)  ─┼──────┼─► BCK           │      │                 │
│  GPIO25 (DATA) ─┼──────┼─► DIN           │      │                 │
│  GPIO22 (WS)   ─┼──────┼─► LCK           │      │                 │
│  3.3V ──────────┼──────┼─► VCC           │      │                 │
│  GND ───────────┼──────┼─► GND           │      │                 │
│                 │      │  LOUT ──────────┼──────┼─► L IN          │
│                 │      │  ROUT ──────────┼──────┼─► R IN          │
│                 │      │  GND ───────────┼──────┼─► GND           │
└─────────────────┘      └─────────────────┘      │  L+/L- ──► 🔊 L │
                                                  │  R+/R- ──► 🔊 R │
                                                  │  12V DC ◄── PSU │
                                                  └─────────────────┘

PCM5102 Configuration

Pin	Connection	Function
FLT	GND	Normal latency
DEMP	GND	De-emphasis off
XSMT	3.3V	Soft mute OFF (audio active)
FMT	GND	I2S format (standard)
SCK	GND	System clock (generated internally)

Hardware Tips

To reduce EMI/interference:

• Keep I2S wires short (<10cm) and twisted together
• Route wires away from the ESP32 antenna (the corner with the metal shield)
• Add ferrite beads on I2S lines
• Use separate power supplies for ESP32 and amplifier
• Add decoupling capacitors (100nF + 10µF) near ESP32 and DAC

To reduce volume with TPA3116:

• Check for gain jumpers on your TPA3116 module (20dB/26dB/32dB)
• Add a resistor voltage divider between DAC and amp:

  PCM5102 LOUT ──[10kΩ]──┬── TPA3116 L IN
                         │
                       [1kΩ]
                         │
                        GND
  

Software Setup

Prerequisites

• PlatformIO (VS Code extension or CLI)

Configuration

Edit AudioMultiRoomClient/include/config.h:

// Room name (visible as Bluetooth speaker name)
#define ROOM_NAME "LivingRoom"

// ESP-NOW channel (0 = auto, or fixed 1-13)
#define ESPNOW_CHANNEL 0

Build & Upload

Using VS Code: Use PlatformIO toolbar buttons (Build, Upload, Monitor)

Using CLI:

cd AudioMultiRoomClient

# Build
pio run

# Upload to ESP32
pio run --target upload

# Serial monitor
pio device monitor

Usage

1. Power on the ESP32
2. You'll hear a "bip-bip" startup sound
3. Connect via Bluetooth from your phone (look for the room name)
4. You'll hear a "ta-da" connection sound
5. Play audio — it comes out of the speaker!
6. On disconnect, you'll hear a descending "da-ta" sound

Libraries

• ESP32-A2DP — Bluetooth A2DP Sink
• arduino-audio-tools — Audio framework (for ESP-NOW, currently disabled)
• arduino-libsbc — SBC codec (for ESP-NOW, currently disabled)

License

MIT License