CNRS AW2ETH

ESP32 board with Ethernet and sensor support - developed for academic and industrial automation projects.

Pinout

ESP32

MCU

240MHz

clock

4MB

flash

520KB

SRAM

21· 16 ADC

GPIO

BLE 4.2+ WiFi

radio

Pinout

21 pins

View:

Pin	GPIO	Labels	Status	Capabilities
1	0	A11T1	strapping	adc · touch
2	1	TXPWM	uart	uart
3	2	A12T2PWM	strapping	adc · touch
4	3	RXPWM	uart	uart
5	4	SCKA10T0PWM	strapping	adc · touch · spi
6	5	SSPWM	strapping	spi
7	9	SDAPWM	strapping	i2c
8	10	SCLPWM	strapping	i2c
9	12	A15T5PWM	strapping	adc · touch
10	13	MISOA14T4PWM	strapping	adc · touch · spi
11	14	MOSIA16T6PWM	strapping	adc · touch · spi
12	15	A13T3PWM	strapping	adc · touch
13	25	A18DAC1PWM	safe	adc · dac
14	26	A19DAC2PWM	safe	adc · dac
15	27	A17T7PWM	safe	adc · touch
16	32	A4T9PWM	safe	adc · touch
17	33	A5T8PWM	safe	adc · touch
18	34	A6	strapping	adc
19	35	A7	strapping	adc
20	36	A0	strapping	adc
21	39	A3	strapping	adc

Start with these

5 pins with no boot or system involvement

A18DAC1A19DAC2A17T7A4T9A5T8

Freely assignable - no strapping, flash, USB or JTAG duties. Ideal first picks for buttons, sensors and LEDs.

Fine - with a little care

sampled at boot or shared with debug/serial

Pin	Label	What to know	Role
A11	GPIO0	Must be HIGH during boot for normal startup; if held LOW on reset, forces flash programming mode.	Strapping
A12	GPIO2	If driven HIGH on reset (while IO0 is LOW), selects an unsupported SDIO boot mode, causing boot failure.	Strapping
SCK	GPIO4	Sampled at reset for boot config; should not be driven at boot (affects boot mode timing).	Strapping
SS	GPIO5	Must be HIGH during boot; if pulled LOW at reset, alters SDIO slave timing and may prevent normal boot.	Strapping
A15	MTDI (GPIO12)	Keep LOW during boot (internal PD); pulling HIGH at reset selects 1.8V flash mode, causing flash brownout if 3.3V flash is used.	Strapping
MISO	MTCK (GPIO13)	Used for JTAG debugging (TCK); avoid using as GPIO if JTAG is needed.	Other
MOSI	MTMS (GPIO14)	Used for JTAG debugging (TMS); driving it as GPIO may interfere with JTAG or produce spurious signals at boot.	Other
A13	MTDO (GPIO15)	Keep HIGH during boot (internal PU); if LOW on reset, bootloader log is silenced and boot mode may change.	Strapping
A6	GPIO34	Cannot be used as output (no drive capability); only suitable for analog/digital input.	Other
A7	GPIO35	Cannot be used as output; only suitable for input.	Other
A0	GPIO36 (SENSOR_VP)	Cannot be used as output; only suitable for input (e.g., analog read).	Other
A3	GPIO39 (SENSOR_VN)	Cannot be used as output; only suitable for input.	Other

Only if you know the tricks

wired to flash or USB - expect a fight

Pin	Label	What to know	Role
TX	U0TXD (GPIO1)	Connected to on-board USB-UART for uploading and logs; drives serial output at boot, so using as GPIO can disrupt programming or console.	USB
RX	U0RXD (GPIO3)	Used for receiving data from USB-UART (programming); also pulled HIGH at boot for console communication, so using as GPIO can disrupt uploads.	USB
SDA	GPIO9 (Flash SD2)	Used by internal flash/PSRAM; typically not exposed on modules, avoid using as GPIO.	Flash
SCL	GPIO10 (Flash SD3)	Used by internal flash/PSRAM; typically not exposed on modules, avoid using as GPIO.	Flash

These are recommendations, not hard rules - with the right pull-ups, timing and boot-state awareness most pins can be made to work. When in doubt, start green.

Pinout notes All 21 pins on the CNRS AW2ETH are usable GPIO. Peripheral wiring is straightforward: I²C is mapped to SDA on GPIO9 and SCL on GPIO10; the SPI bus ( MOSI ,…

All 21 pins on the CNRS AW2ETH are usable GPIO.

Peripheral wiring is straightforward: I²C is mapped to SDA on GPIO9 and SCL on GPIO10; the SPI bus (MOSI, MISO, SCK, SS) is broken out in full; TX/RX on GPIO1 and GPIO3 cover serial logging and flashing.

Beyond plain digital I/O you get 16 ADC-capable pins for sensors and battery monitoring, 10 capacitive-touch inputs and 2 true DAC outputs.

12 of the exposed pins carry boot-time or system duties on the ESP32 (A11, A12, SCK and 9 more) - check the guidance above before wiring anything to them. A18, A19, A17, A4 and 1 more are free of any such role - the safest first picks.

Getting started

flash your first firmware in ~2 minutes

Tool:

Connect over USB

Install your USB-serial driver (CH340 / CP210x) if no port appears. Not detected? Hold BOOT while plugging in.

Match & flash

Set the Tools options shown, then click Upload.

Verify it runs

The onboard LED on GPIO25 blinks - swap the pin if your board's LED differs.

Set these in Tools · leave everything else at default

Arduino IDE 2.x — Tools Copy

Board: "ESP32 Dev Module"▸

Flash Size: "4MB (32Mb)"▸

Flash Mode: "DIO"▸

Partition Scheme: "Default 4MB with spiffs (1.2MB APP / 1.5MB SPIFFS)" (default)▸

Upload Speed: "921600"▸

▸ every other Tools option — leave at default

Board: ESP32 Dev Module
Flash Size: 4MB (32Mb)
Flash Mode: DIO
Partition Scheme: Default 4MB with spiffs (1.2MB APP / 1.5MB SPIFFS)
Upload Speed: 921600

Find it: Tools ▸ Board ▸ ESP32 Arduino ▸ ESP32 Dev Module

blink.ino Copy

// blink the onboard LED
void setup() {
  pinMode(25, OUTPUT);
}
void loop() {
  digitalWrite(25, HIGH); delay(500);
  digitalWrite(25, LOW);  delay(500);
}

board to selectesp32dev⧉ copy

platformio.ini Copy

[env:aw2eth]
platform = espressif32
board = esp32dev
framework = arduino
monitor_speed = 115200
upload_speed = 921600

Find it: PlatformIO Home ▸ Boards, search esp32dev — or type it after board =.

board to selectesp32dev⧉ copy

device.yaml Copy

esp32:
  board: esp32dev
  variant: cnrs_aw2eth
  framework:
    type: esp-idf

# blink - GPIO25
output:
  - platform: gpio
    pin: 25
    id: led_out
light:
  - platform: binary
    name: "LED"
    output: led_out

Find it: search ESPHome's board list for esp32dev (same ids as PlatformIO).

esptool doesn't pick board settings — a prebuilt .bin already has them baked in. This is just the raw flash command.

terminal Copy

esptool.py --chip esp32 --port /dev/ttyACM0 \
  --baud 921600 write_flash 0x0 firmware.bin

--port = your /dev/tty* (macOS/Linux) or COMx (Windows).

Build details: sketch space 1310720 B · data 327680 B · DIO

Specifications

ESP32

Compute

MCU

ESP32

Clock

240 MHz

SRAM · Flash

520 KB · 4MB

Radio

Wi-Fi

802.11 b/g/n

Bluetooth

4.2 LE

Antenna

PCB

I/O

GPIO · ADC

21 · 16

UART · I²C · SPI

3 · 2 · 4

PWM

16 channels

Power

USB

Serial

Boot address

0x1000

Flashing

Upload · OTA

esptool_py · esp_ota

Flash · Boot mode

DIO · DIO

Sketch · Data

1.25 MB · 320 KB

The CNRS AW2ETH uses esptool_py for firmware uploads, esp_ota for over-the-air (OTA) updates. Flash mode is DIO with DIO boot mode. The maximum sketch size is 1.25 MB with 320 KB available for data.

About this board

Inside sits the ESP32 - a dual-core Xtensa with both Bluetooth Classic and BLE.

Around the module: wired Ethernet (true).

Resources

ESP32 datasheet espressif.com↗ CNRS AW2ETH - arduino-esp32 variant github.com↗CNRS AW2ETH - PlatformIO board docs.platformio.org↗

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