AI05 Env Sensors

Features

This leaf measures temperature, humidity, pressure and 3-axis acceleration. Combine it with an MCU (microcontroller) leaf to read environmental conditions and the leaf’s tilt and motion.

The standard configuration uses a BME280 temperature, humidity and pressure sensor and a LIS2DW12 3-axis accelerometer. It operates from the Leafony Bus 3.3 V supply, and readings are obtained over I2C. A four-pin connector is available for external I2C devices.

Pads are also provided for SHT40, SGP40 and BME680 sensors. These are not fitted as standard. Using them requires the components and program described under optional assembly.

Specifications

Board and interfaces

Item	Description
Board dimensions	23 × 20 mm
Board thickness	0.8 mm (excluding component height)
Board layers	4
Power and signal voltage	3.3 V
Communication	I2C, up to 400 kHz
Acceleration interrupt	LIS2DW12 INT1 connected to Leafony Bus D3
External connector J1	4 pins, 2.54 mm pitch, for a right-angle pin header
SDA/SCL pull-ups	R18 and R19 (2.7 kΩ each) are not fitted as standard

Standard configuration

Reference	Part	Manufacturer	Measurements
U3	BME280	Bosch Sensortec	Temperature, humidity and pressure
U5	LIS2DW12TR	STMicroelectronics	3-axis acceleration

The BME280 operating temperature range is −40 to 85 °C, and the pressure measurement range is 300 to 1100 hPa. Accuracy conditions depend on temperature; see the BME280 manufacturer documentation.

The LIS2DW12 acceleration range can be set to ±2 g, ±4 g, ±8 g or ±16 g (manufacturer documentation).

Optional assembly

DNP (Do Not Populate) means the component is not fitted.

Reference	Part	Function	Standard configuration
U1	SHT40-AD1B-R2	Temperature and humidity	DNP
U2	SGP40-D-R4	Gas sensor responding to volatile organic compounds (VOCs)	DNP
U4	BME680	Temperature, humidity, pressure and gas sensor	DNP

The BME280 (U3) and BME680 (U4) have separate footprints, but only one is fitted. Both use I2C address 0x76, so they cannot both be fitted and read independently.

The standard configuration populates U3, C21 and C22, leaving U4, C23 and C24 unpopulated. Reverse that choice to use BME680. SHT40 and SGP40, which are not fitted as standard, will not respond to an I2C scan.

When adding SHT40, also fit C20. When adding SGP40, also fit R10 (4.7 Ω), C2 and C3. These are also unpopulated as standard; without R10, SGP40 receives no power.

Gas measurement is not included in the standard configuration. Using metrics such as SGP40’s VOC Index requires the sensor and corresponding signal processing (SGP40 manufacturer information, BME680 manufacturer information).

I2C addresses

All addresses use 7-bit notation.

Device	Address	Configuration
LIS2DW12	0x18	Standard; SDO/SA0 connected to GND
BME280	0x76	Standard; SDO connected to GND
SHT40	0x44	Optional
SGP40	0x59	Optional
BME680	0x76	Alternative to BME280; SDO connected to GND

Pin connections

Leafony Bus

Signal	Connector contacts	AI05 function
V33	F1 / B1	3.3 V power
SDA	F23 / B23	I2C data
D3	F24 / B24	LIS2DW12 INT1 interrupt
SCL	F25 / B25	I2C clock
GND	F27 / B27	Power and signal ground

F/B are the front/back contact names on the KiCad Leafony Bus connector CN1. LIS2DW12 INT2 is not connected. See the Leafony Bus for the overall bus specification.

External I2C connector J1

Pin	Signal	Function
1	GND	Power and signal ground
2	+3.3V	Leafony Bus 3.3 V supply
3	SDA	I2C data
4	SCL	I2C clock

J1 accepts a four-pin, 2.54 mm pitch header and shares the Leafony Bus power and I2C bus. Check pin numbers and 3.3 V compatibility before attaching cables or external devices.

Connection requirements

• Check the I2C pull-ups. R18 and R19 are not fitted. When paired with AP03 STM32 MCU, the pull-ups on AP03 are used. For other MCUs and external devices, also check that SDA/SCL are pulled up to 3.3 V.
• The I2C address conflicts with AX06 Grove&5V. AI05’s LIS2DW12 and AX06’s I/O expander both use 0x18. Do not connect them to the same bus with their standard settings.
• The D3 interrupt line conflicts with AI01 4-Sensors. AI05 uses acceleration address 0x18 and AI01 uses 0x19, but the interrupt line is shared, so do not combine them unchanged. If SHT40 is added, 0x44 may also conflict, depending on the address setting of AI01’s light sensor.
• Devices connected to J1 also share the I2C bus. Check the I2C address map for conflicts with other leaves.

PCB layout

These reference images were generated from the KiCad board data. They omit component 3D models and include pads for optional components. See standard configuration and optional assembly for fitted and unpopulated components.

Top

Bottom

Software

Initialize I2C on the MCU and read BME280 at 0x76 and LIS2DW12 at 0x18. Follow each manufacturer’s documentation for initialization, compensation calculations and register settings.

AI01 4-Sensors uses different sensors, so its temperature/humidity and acceleration examples cannot be used unchanged. The referenced repository does not yet include AI05 example programs.

Documents

• AI05 Env Sensors repository
• KiCad project
• KiCad schematic
• KiCad PCB layout
• Panelized manufacturing data
• BME280 manufacturer information
• LIS2DW12 manufacturer information
• SHT40 manufacturer information
• SGP40 manufacturer information
• BME680 manufacturer information

Revision history

• September 2026: Initial version.