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Wiring Guide

Microphone Input

Current Implementation: Analog Microphone via TRRS (ADC)

This configuration uses an analog electret microphone (like a standard headset mic) connected through the ESP32-S3 using the MAX 9814 microphone amplifier module.

MAX9814 Pin ESP32-S3
VDD 3.3V
GND GND
OUT GPIO1 (ADC)
AR Leave floating (default attack/release)
GAIN VDD (40dB), GND (50dB) or floating (60dB)

3.5mm TRS JACK CONNECTIONS:

TRRS MAX9814
TIP MIC+
RING1 (NC)
RING2 (NC)
SLEEVE GND

Ring 1, Ring 2 or Tip can be used for MIC+ depending on the TRRS implementation.

ADC Configuration:

  • Channel: ADC1_CHANNEL_0 (GPIO1)
  • Sample rate: 16 kHz
  • Bit width: 12-bit (ESP32-S3 native)
  • Attenuation: 2.5dB

Alternative: I2S Digital Microphone (INMP441)

The original design planned for an INMP441 I2S digital microphone. If switching to I2S digital:

INMP441 Pin ESP32-S3 Pin Function
SCK GPIO 4 BCLK (Bit Clock)
WS GPIO 5 WS (Word Select)
SD GPIO 6 DIN (Data In)
L/R GND Left channel select
VDD 3.3V Power
GND GND Ground

Note: Code changes required to switch from ADC to I2S RX mode.

Speaker

MAX98357A I2S Amplifier (Speaker Output)

The MAX98357A is a mono I2S Class-D amplifier. It connects to the ESP32-S3 via the I2S interface.

MAX98357A Pin ESP32-S3 Pin Function Notes
LRC GPIO 5 WS (Word Select) Left/Right Clock
BCLK GPIO 4 SCK (Bit Clock) Serial Clock
DIN GPIO 7 DOUT (Data Out) Audio Data
GAIN GND Gain Setting Sets +9dB gain (adjust as needed)
SD Floating Shutdown / Channel Left + Right / 2 (Mono Mix)
GND GND Ground Common Ground
VIN 5V or 3.3V Power 5V recommended for full 3W power

Notes:

  • If your board has a "5V" pin, use it for VIN to get louder audio.
  • If using 3.3V, audio power will be limited to ~0.5W.
  • The SD pin can be connected to VCC or GND to change channel selection, but leaving it floating selects "Left/2 + Right/2" which is perfect for mono mix.

Connect SPK+ and SPK- to your speaker. Speaker impedance should be 4-8 Ohms, and the speaker should be 0.5W to 3W for best results.

PCM5102A 3.5mm Audio Jack (Alternative Speaker Output)

PCM5102A ESP32-S3
BCK GPIO4
LCK (LRCK / WS) GPIO5
DIN GPIO7
VIN 3.3V
GND GND

Note: Code changes required to switch from MAX98357A to PCM5102A.

nRF52840 Mesh Radio (XIAO)

The Seeed XIAO nRF52840 handles mesh networking via ESB (Enhanced ShockBurst). Audio packets received from the mesh are sent to ESP32-S3 via SPI for mixing.

SPI Connection

The nRF52840 is the SPI master and the ESP32-S3 is the SPI slave. The master polls the slave every 5 ms with a full-duplex 256-byte transaction.

XIAO nRF52840 ESP32-S3 Function
Pin 6 (P1.11 / MOSI) GPIO10 nRF MOSI -> ESP MOSI
Pin 7 (P1.12 / MISO) GPIO9 ESP MISO -> nRF MISO
Pin 8 (P1.13 / SCK) GPIO11 SPI Clock
Pin 9 (P1.14 / CS) GPIO12 Chip Select (active low)
GND GND Common ground

I2S WS Sync Wire (Clock Discipline)

The ESP32's I2S Word Select (WS) output is tapped and fed to the nRF52840 to discipline the TDMA frame timer. This eliminates clock drift between boards.

ESP32-S3 XIAO nRF52840 Function
GPIO 5 (I2S WS/LCK) Pin D0 (P0.02) Sync clock (16 kHz)

Note: GPIO5 is already wired to the speaker amplifier (MAX98357A/PCM5102A LCK). Simply add a second wire from the same GPIO5 pad to XIAO D0. The nRF input is high-impedance and will not affect the amplifier signal.

Wiring Diagram

ESP32-S3                    XIAO nRF52840
┌──────────┐                ┌──────────┐
│          │                │          │
│   GPIO10 ├────────────────┤ Pin 6    │  (MOSI)
│   GPIO9  ├────────────────┤ Pin 7    │  (MISO)
│   GPIO11 ├────────────────┤ Pin 8    │  (SCK)
│   GPIO12 ├────────────────┤ Pin 9    │  (CS)
│   GPIO5  ├────────────────┤ Pin D0   │  (I2S WS Sync)
│          │                │          │
│   GND    ├────────────────┤ GND      │
│          │                │          │
└──────────┘                └──────────┘

Note: Both boards run at 3.3V logic, no level shifter needed.