Board Configurations

WeSense firmware supports multiple ESP32 board variants. The firmware auto-detects your board type at startup. This page provides detailed pin assignments and board-specific notes for each supported board.

Supported Boards Overview

Board	I2C	Dual I2C	UART	LoRa	Battery/Solar	USB CDC Required
ESP32 DevKit / WROOM-32	21/22	Yes (13/14)	UART2 (16/17)	No	No	No
ESP32-C3 Generic	4/5	No (single controller)	UART1 (20/21)	No	No	Yes
ESP32-C6 Beetle / Generic	19/20	Yes (6/7)	UART1 (17/16)	No	No	Yes
ESP32-S3 Generic	8/9	Yes (17/18)	UART2 (44/43)	No	No	Yes
T-Beam v1.x (Lilygo)	21/22	Yes (13/14)	UART2 (16/17)	SX1276	Yes	No
T-Beam T3 S3 v1.2 (Lilygo)	45/46	Yes (17/18 internal)	UART2 (16/15)	SX1262	Yes	Yes

ESP32 DevKit / WROOM-32

The standard ESP32 development board. Widely available, cheapest option.

Pin Assignments

Function	Pin	Board Label
I2C SDA	GPIO 21	D21
I2C SCL	GPIO 22	D22
Secondary I2C SDA	GPIO 13	D13
Secondary I2C SCL	GPIO 14	D14
UART2 RX	GPIO 16	D16
UART2 TX	GPIO 17	D17

Sensor Wiring

ESP32 DevKit     →    I2C Sensors
─────────────         ────────────
GPIO 21 (SDA)    →    SDA
GPIO 22 (SCL)    →    SCL
3V3              →    VCC
GND              →    GND

ESP32 DevKit     →    PMS5003/C8
─────────────         ────────────
GPIO 16 (RX)     →    TX
GPIO 17 (TX)     →    RX
VIN (5V)         →    VCC
GND              →    GND

ESP32-C3 Generic

Compact RISC-V board. Budget-friendly but has a single I2C controller limitation.

Pin Assignments

Function	Pin
I2C SDA	GPIO 4
I2C SCL	GPIO 5
Alt I2C SDA	GPIO 8 (same controller, different pins)
Alt I2C SCL	GPIO 9 (same controller, different pins)
UART1 RX	GPIO 20
UART1 TX	GPIO 21
Built-in LED	GPIO 8

Important Notes

Single I2C controller — unlike other ESP32 variants, the C3 cannot run two independent I2C buses. The alternative pins (8/9) use the same controller as the primary (4/5).
Uses UART1 (not UART2) — the firmware handles this automatically.
Requires USB CDC On Boot enabled in Arduino IDE.

Sensor Wiring

ESP32-C3         →    I2C Sensors
─────────────         ────────────
GPIO 4 (SDA)     →    SDA
GPIO 5 (SCL)     →    SCL
3V3              →    VCC
GND              →    GND

ESP32-C3         →    PMS5003/C8
─────────────         ────────────
GPIO 20 (RX)     →    TX
GPIO 21 (TX)     →    RX
VIN (5V)         →    VCC
GND              →    GND

I2C Conflict Workarounds

Since you can't isolate sensors on separate buses:

Use sensors with unique I2C addresses
Keep I2C cable runs short (under 20cm)
Add external 4.7k pull-up resistors if using longer cables
If conflicts persist, consider upgrading to a C6 or S3 board

ESP32-C6 Beetle (DFRobot) / Generic

WiFi 6 board with dual I2C. The Beetle variant is ultra-compact (23x28mm).

Pin Layout (Beetle)

                    ESP32-C6 Beetle Mini
    ┌──────────────────────────────────────────────────────────┐
    │                      USB-C                               │
    │  ┌─────────────────────────────────────────────────┐     │
    │  │                                                 │     │
    │  │               DFRobot Logo                      │     │
    │  │                                                 │     │
    │  └─────────────────────────────────────────────────┘     │
    │                                                          │
    ├──────────────────────────────────────────────────────────┤
    │  VIN  │ GND │ 3V3 │ EN  │ 0   │ 1   │ 18  │ 8   │
    │  23   │ 9   │ 21  │ 22  │ 19  │ 20  │ 10  │ 11  │
    │       │     │     │     │ SDA │ SCL │ 4   │ 5   │
    │  12   │ 13  │ 14  │ 15  │ 16  │ 17  │ 6   │ 7   │
    │       │     │     │ LED │ TX  │ RX  │LP_SDA│LP_SCL│
    │  2    │ 3   │     │     │     │     │     │     │
    └──────────────────────────────────────────────────────────┘

Pin Assignments

Function	Pin	Label
I2C SDA	GPIO 19	SDA
I2C SCL	GPIO 20	SCL
Secondary I2C SDA	GPIO 6	LP_SDA
Secondary I2C SCL	GPIO 7	LP_SCL
UART1 RX	GPIO 17	RX
UART1 TX	GPIO 16	TX
Built-in LED	GPIO 15	LED

Important Notes

WiFi 6 (802.11ax) — more efficient than older WiFi standards.
Dual I2C controllers — can isolate pressure sensors on the secondary bus.
Uses UART1 (not UART2) — firmware handles automatically.
Requires USB CDC On Boot enabled in Arduino IDE.
Thread/Matter radio built in (802.15.4) — not used by WeSense currently but future-ready.

Boot Button Display Control

The boot button (GPIO 0) provides convenient display control:

Display timed out (after 10 minutes): press to turn back on
Display active: press to reset the 10-minute timeout

Sensor Wiring

ESP32-C6         →    I2C Sensors
─────────────         ────────────
GPIO 19 (SDA)    →    SDA
GPIO 20 (SCL)    →    SCL
3V3              →    VCC
GND              →    GND

ESP32-C6         →    PMS5003/C8
─────────────         ────────────
GPIO 17 (RX)     →    TX
GPIO 16 (TX)     →    RX
VIN (5V)         →    VCC
GND              →    GND

ESP32-S3 Generic

Higher-performance dual-core board with dual I2C.

Pin Assignments

Function	Pin
I2C SDA	GPIO 8
I2C SCL	GPIO 9
Secondary I2C SDA	GPIO 17
Secondary I2C SCL	GPIO 18
UART2 RX	GPIO 44
UART2 TX	GPIO 43
Built-in LED	GPIO 48 (common)

Important Notes

Dual-core with enhanced processing power and 2MB+ RAM.
Dual I2C controllers — can isolate sensors.
Requires USB CDC On Boot enabled in Arduino IDE.

Sensor Wiring

ESP32-S3         →    I2C Sensors
─────────────         ────────────
GPIO 8 (SDA)     →    SDA
GPIO 9 (SCL)     →    SCL
3V3              →    VCC
GND              →    GND

ESP32-S3         →    PMS5003/C8
─────────────         ────────────
GPIO 44 (RX)     →    TX
GPIO 43 (TX)     →    RX
VIN (5V)         →    VCC
GND              →    GND

T-Beam v1.x (Lilygo)

Classic LoRaWAN board with built-in 18650 battery holder, solar charge controller, and GPS.

Pin Assignments

Function	Pin
I2C SDA	GPIO 21
I2C SCL	GPIO 22
Secondary I2C SDA	GPIO 13
Secondary I2C SCL	GPIO 14
UART2 RX	GPIO 16
UART2 TX	GPIO 17
GPS TX	GPIO 12
GPS RX	GPIO 34
Built-in LED	GPIO 4
LoRa (SX1276)	SPI: SCK=5, MISO=19, MOSI=27, CS=18, RST=23, DIO0=26

Key Features

SX1276 LoRa radio — original LoRa chip, good range
AXP192 PMU — battery charging, solar input, power monitoring via I2C
Built-in 18650 battery holder — convenient but adds size
External battery connector — also available if you prefer a different battery
GPS — auto-detects location

Important Notes

The AXP192 PMU is on the primary I2C bus — external sensors share this bus.
Does not require USB CDC On Boot (uses external USB-Serial chip).

Sensor Wiring

T-Beam v1.x      →    I2C Sensors
─────────────         ────────────
GPIO 21 (SDA)    →    SDA
GPIO 22 (SCL)    →    SCL
3V3              →    VCC
GND              →    GND

T-Beam v1.x      →    PMS5003/C8
─────────────         ────────────
GPIO 16 (RX)     →    TX
GPIO 17 (TX)     →    RX
5V               →    VCC
GND              →    GND

T-Beam T3 S3 v1.2 (Lilygo)

Newer LoRaWAN board with SX1262 radio, LiPo battery socket, solar charge controller, and GPS. The recommended LoRa board for new builds.

Pin Assignments

Function	Pin	Notes
I2C SDA (internal)	GPIO 17	Hardwired to AXP2101 PMU and OLED
I2C SCL (internal)	GPIO 18	Hardwired to AXP2101 PMU and OLED
I2C SDA (external sensors)	GPIO 45	Use this for your sensors
I2C SCL (external sensors)	GPIO 46	Use this for your sensors
UART2 TX	GPIO 15
UART2 RX	GPIO 16
Built-in LED	GPIO 4
LoRa (SX1262)	SPI: SCK=5, MISO=3, MOSI=6, CS=7, RST=8, DIO1=33, BUSY=34

Key Features

SX1262 LoRa radio — newer generation, better range and lower power than SX1276 (despite the lower model number)
AXP2101 PMU — battery charging, solar input, power monitoring
LiPo battery socket — more compact than the 18650 holder on the v1.x, and you can connect any LiPo battery
GPS — auto-detects location

Important Notes

External sensors must use GPIO 45/46 — the primary I2C bus (17/18) is hardwired to internal components (PMU, OLED) and is not easily accessible for external sensors.
Requires USB CDC On Boot enabled in Arduino IDE.

Sensor Wiring

T-Beam T3 S3     →    I2C Sensors
─────────────         ────────────
GPIO 45 (SDA)    →    SDA          ← NOT GPIO 17!
GPIO 46 (SCL)    →    SCL          ← NOT GPIO 18!
3V3              →    VCC
GND              →    GND

T-Beam T3 S3     →    PMS5003/C8
─────────────         ────────────
GPIO 16 (RX)     →    TX
GPIO 15 (TX)     →    RX
5V/VBUS          →    VCC
GND              →    GND

I2C Bus Isolation (Advanced)

If you experience stuck or erratic pressure sensor readings, you can isolate pressure sensors on the secondary I2C bus. This is supported on all boards with dual I2C controllers (everything except ESP32-C3).

Enable in firmware configuration:

cpp

const bool ISOLATE_PRESSURE_SENSORS = true;

When enabled, the following sensors move to the secondary I2C bus:

BMP390 (pressure)
BMP280 (pressure)
AHT20 (temperature/humidity backup)

All other sensors stay on the primary bus. The firmware auto-detects which bus each sensor is connected to.

Secondary I2C Pin Summary

Board	Secondary SDA	Secondary SCL
ESP32 DevKit / WROOM-32	GPIO 13	GPIO 14
T-Beam v1.x	GPIO 13	GPIO 14
T-Beam T3 S3 v1.2	GPIO 45/46 are already the external bus
ESP32-S3 Generic	GPIO 17	GPIO 18
ESP32-C6 Beetle / Generic	GPIO 6 (LP_SDA)	GPIO 7 (LP_SCL)
ESP32-C3 Generic	Not supported (single I2C controller)

General Wiring Tips

I2C Daisy Chain

All I2C sensors connect to the same SDA/SCL pins in parallel:

Board SDA  ──┬── Sensor 1 SDA ──┬── Sensor 2 SDA ──┬── Sensor 3 SDA
Board SCL  ──┬── Sensor 1 SCL ──┬── Sensor 2 SCL ──┬── Sensor 3 SCL
Board 3.3V ──┬── Sensor 1 VCC ──┬── Sensor 2 VCC ──┬── Sensor 3 VCC
Board GND  ──┬── Sensor 1 GND ──┬── Sensor 2 GND ──┬── Sensor 3 GND

UART TX/RX Crossover

UART sensors cross TX and RX — this is the most common wiring mistake:

Board RX  ──→  Sensor TX
Board TX  ──→  Sensor RX
Board 5V  ──→  Sensor VCC   (must be 5V, not 3.3V)
Board GND ──→  Sensor GND

Power

I2C sensors: 3.3V from the board's 3V3 pin
UART sensors (PMS5003, C8 CO2): 5V from the board's VIN or 5V pin. Not all board designs break out a 5V pin — check your specific board.
CM1106-C CO2: Requires 5V power (4.5-5.5V) but uses I2C at 3.3V logic levels

Board Configurations ​

Supported Boards Overview ​

ESP32 DevKit / WROOM-32 ​

Pin Assignments ​

Sensor Wiring ​

ESP32-C3 Generic ​

Pin Assignments ​

Important Notes ​

Sensor Wiring ​

I2C Conflict Workarounds ​

ESP32-C6 Beetle (DFRobot) / Generic ​

Pin Layout (Beetle) ​

Pin Assignments ​

Important Notes ​

Boot Button Display Control ​

Sensor Wiring ​

ESP32-S3 Generic ​

Pin Assignments ​

Important Notes ​

Sensor Wiring ​

T-Beam v1.x (Lilygo) ​

Pin Assignments ​

Key Features ​

Important Notes ​

Sensor Wiring ​

T-Beam T3 S3 v1.2 (Lilygo) ​

Pin Assignments ​

Key Features ​

Important Notes ​

Sensor Wiring ​

I2C Bus Isolation (Advanced) ​

Secondary I2C Pin Summary ​

General Wiring Tips ​

I2C Daisy Chain ​

UART TX/RX Crossover ​

Power ​

Board Configurations

Supported Boards Overview

ESP32 DevKit / WROOM-32

Pin Assignments

Sensor Wiring

ESP32-C3 Generic

Pin Assignments

Important Notes

Sensor Wiring

I2C Conflict Workarounds

ESP32-C6 Beetle (DFRobot) / Generic

Pin Layout (Beetle)

Pin Assignments

Important Notes

Boot Button Display Control

Sensor Wiring

ESP32-S3 Generic

Pin Assignments

Important Notes

Sensor Wiring

T-Beam v1.x (Lilygo)

Pin Assignments

Key Features

Important Notes

Sensor Wiring

T-Beam T3 S3 v1.2 (Lilygo)

Pin Assignments

Key Features

Important Notes

Sensor Wiring

I2C Bus Isolation (Advanced)

Secondary I2C Pin Summary

General Wiring Tips

I2C Daisy Chain

UART TX/RX Crossover

Power