Adafruit Si7021 Temperature & Humidity Sensor Breakout Board

I2C temperature and humidity sensor breakout based on the Si7021. Works at 3.3 V or 5 V with onboard level shifting and pull-ups, suitable for weather stations and HVAC monitoring.

Logical pinout · physical placement not verified

VinVin
Board power input. Adafruit states the onboard regulator accepts 3 to 5 VDC and safely converts it down for the Si7021 breakout.
Type · PowerVoltage · 3-5V input
3v33v3
3.3V output from the onboard voltage regulator. Adafruit states up to 100 mA can be drawn from this output.
Type · PowerVoltage · 3.3V output, up to 100 mA
GNDGND
Common ground for power and logic.
Type · Ground
SCLSCL
I2C clock pin. Connects to the microcontroller I2C clock line. Adafruit states the fixed I2C address is 0x40.
Type · I2CVoltage · Logic level follows host/power wiring
SDASDA
I2C data pin. Connects to the microcontroller I2C data line. Adafruit states the fixed I2C address is 0x40.
Type · I2CVoltage · Logic level follows host/power wiring
STEMMA QTSTEMMA QT
STEMMA QT / Qwiic connector carrying the board I2C and power connections for plug-and-play chaining.
Type · UnknownVoltage · 3-5V board power, I2C signals

Pin	Position	Type	Function	Voltage
Vin	Vin	Power	Board power input. Adafruit states the onboard regulator accepts 3 to 5 VDC and safely converts it down for the Si7021 breakout.	3-5V input
3v3	3v3	Power	3.3V output from the onboard voltage regulator. Adafruit states up to 100 mA can be drawn from this output.	3.3V output, up to 100 mA
GND	GND	Ground	Common ground for power and logic.
SCL	SCL	I2C	I2C clock pin. Connects to the microcontroller I2C clock line. Adafruit states the fixed I2C address is 0x40.	Logic level follows host/power wiring
SDA	SDA	I2C	I2C data pin. Connects to the microcontroller I2C data line. Adafruit states the fixed I2C address is 0x40.	Logic level follows host/power wiring
STEMMA QT	STEMMA QT	Unknown	STEMMA QT / Qwiic connector carrying the board I2C and power connections for plug-and-play chaining.	3-5V board power, I2C signals

Logical pinout · physical placement not verified

Pin details

6 connections

Vin
Board power input. Adafruit states the onboard regulator accepts 3 to 5 VDC and safely converts it down for the Si7021 breakout.
PowerVoltage · 3-5V input
Vin
3v3
3.3V output from the onboard voltage regulator. Adafruit states up to 100 mA can be drawn from this output.
PowerVoltage · 3.3V output, up to 100 mA
3v3
GND
Common ground for power and logic.
Ground
GND
SCL
I2C clock pin. Connects to the microcontroller I2C clock line. Adafruit states the fixed I2C address is 0x40.
I2CVoltage · Logic level follows host/power wiring
SCL
SDA
I2C data pin. Connects to the microcontroller I2C data line. Adafruit states the fixed I2C address is 0x40.
I2CVoltage · Logic level follows host/power wiring
SDA
STEMMA QT
STEMMA QT / Qwiic connector carrying the board I2C and power connections for plug-and-play chaining.
UnknownVoltage · 3-5V board power, I2C signals
STEMMA QT

Start wiring

I2C · SPI · Single data line · 3.3 – 5 V · Breakout

Confirm the data interface matches your host board.

Module pins: Vin, 3v3, GND, SCL, SDA. Schematik maps them to your board in the app.

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