Future board bench (ESP32-S3 + ESP32)

This is not the current setup

This page is for the future all-in-one board, prototyped with two ESP32 devkits (an ESP32-S3 and an ESP32) and the InnoMaker amplifier, with no Raspberry Pi. The build running today is a Raspberry Pi 3 + HiFiBerry Amp2 + one ESP32 DevKit for the light: see Wiring — current setup.

The bench prototypes the future all-in-one board (robine_board v1.1) on a breadboard, with Dupont wires. GPIO numbers and net names are those of the board, so firmware written on the bench runs unchanged on it — except the amplifier driver (the InnoMaker uses an MA12070P, the board a TAS5825M).

Part	Role
ESP32-S3-DevKitC-1 (N16R8) — S3	master: AirPlay, I²S master, LoRa, LED
ESP32-DevKitC (WROOM-32E) — ESP32	Bluetooth A2DP receiver, I²S slave
InnoMaker HiFi AMP Pro Mini (MA12070P) — HAT	I²S slave, I²C 0x20, 9–24 V
RFM95W	LoRa 868 MHz, 3.3 V only, antenna mandatory
SK6812	one LED, 5 V through a diode
Small parts	2 × 4.7 kΩ, 1 × 330 Ω, 1N4148, 100 nF, 10 µF
Amplifier supply	regulated 19–20 V, ≥ 4 A, 5.5 mm jack (never a 24 V adapter: see the Zero W power tolerances)
Speakers	4–8 Ω, bridged (BTL)

Rules

• One common ground row on the breadboard: every GND meets there.
• Never 5 V on a 3.3 V pin. Never transmit without the LoRa antenna.
• A speaker “−” is never connected to GND.
• Power the amplifier last; never hot-plug its supply.

Where to start

Do the figures in this order, powering up and checking after each one: 1 S3 ↔ ESP32, 2 S3 ↔ amplifier, 3 LoRa, 4 LED, 5 power and speakers.

1. S3 ↔ ESP32 (Bluetooth audio)

UARTSignalI²S audioGround

The S3 generates the I²S clocks, the ESP32 sends the Bluetooth audio back on I2S_BT_DOUT.

I2S_BCLK and I2S_LRCLK also go to the amplifier (next figure): run one wire from the S3 to a breadboard row, then one wire from that row to each destination.

2. S3 ↔ InnoMaker amplifier

The HAT’s 40-pin connector keeps the Raspberry Pi pin numbers. Odd pins on the left (inner row), even pins on the right; pin 1 is the square pad.

3.3 VI²CGroundSignalI²S audio

Pins wired on the bench. The 5 V pins (2 and 4) stay unconnected.

I²S audioI²CSignalGround3.3 V

I²C: 4.7 kΩ pull-up to 3V3 on SDA and on SCL (the HAT relies on the Pi's pull-ups). Pins 8, 10 and 16 come from the Linux merus-amp overlay: verify them (check 3).

3. S3 ↔ LoRa module (RFM95W)

SPISignal3.3 VGround

3.3 V only. Put 10 µF + 100 nF between 3.3 V and GND at the module (it peaks near 120 mA when transmitting). Antenna first.

4. Status LED (SK6812)

SignalPower (+)Ground

The diode drops the LED supply to about 4.3 V, which lowers the data threshold to about 3 V: the S3's 3.3 V signal is enough, no level shifter. Add 100 nF between VDD and GND at the LED.

5. Amplifier power and speakers

Power (+)GroundSpeaker

Bridged outputs: the − of a speaker goes to the amplifier's − terminal, never to GND.

Checks before the first power-up

1. Amplifier alone, powered, measure pin 1 of its connector. About 3.3 V: the HAT makes its own 3.3 V, so do not join the S3’s 3V3 (leave the dashed wire out). Nothing there: join it.
2. Still alone and powered, measure SDA and SCL (pins 3 and 5): 0 V or 3.3 V, never 5 V.
3. Unpowered, with a continuity tester, check that pins 8, 10 and 16 go to the MA12070P’s enable, mute and error functions. If not, leave those wires out.
4. Do not connect the HAT’s 5 V pins (2 and 4): it outputs 5 V (it normally feeds a Raspberry Pi) and would fight the devkits’ USB.

Power-up order

1. All wires in place, grounds first.
2. Speakers connected (bridged).
3. Antenna on the RFM95W.
4. USB on both devkits.
5. Amplifier jack plugged, then the mains adapter switched on.

Flashing the ESP32

• From its own USB (daily use): unplug BT_RXD0 and leave the S3 idle, its IO47 and IO48 as inputs.
• Through the S3 (to test the board’s mechanism): plug BT_RXD0 back and close any serial monitor on the ESP32. The S3 pulls IO0 low, resets it via EN and speaks the ROM bootloader protocol on its UART.

Reference table

Net	From	To
BT_RXD0	S3 IO15 (TX)	ESP32 RX (IO3)
BT_TXD0	ESP32 TX (IO1)	S3 IO16 (RX)
BT_EN / BT_IO0	S3 IO47 / IO48	ESP32 EN / IO0
I2S_BCLK	S3 IO6	HAT pin 12 + ESP32 IO26
I2S_LRCLK	S3 IO7	HAT pin 35 + ESP32 IO25
I2S_DOUT	S3 IO8	HAT pin 40
I2S_BT_DOUT	ESP32 IO22	S3 IO40
I2C_SDA / SCL	S3 IO17 / IO18	HAT pins 3 / 5 (+ 4.7 kΩ to 3V3)
AMP_PDN	S3 IO21	HAT pin 8
AMP_MUTE	S3 IO41	HAT pin 10
AMP_FAULT	HAT pin 16	S3 IO38
SPI_SCK / MOSI / MISO	S3 IO12 / IO11 / IO13	RFM95W SCK / MOSI / MISO
LORA_CS / RST / DIO0	S3 IO10 / IO14 / IO39	RFM95W NSS / RESET / DIO0
STATUS_LED	S3 IO42	330 Ω → SK6812 DIN
LED_VDD	S3 5V	1N4148 → SK6812 VDD
GND	common row	both devkits, HAT pin 6, RFM95W, LED

Source of truth: hardware/dev_bench and the mainboard README.