The PCA9306 Module with Arduino Uno is a bidirectional logic level translator designed specifically for I²C bus communication. It allows devices operating at different voltage levels - such as 5V microcontrollers and 3.3V sensors - to communicate safely and reliably. Instead of using discrete MOSFET-based level-shifting circuits, the PCA9306 integrates this functionality into a single IC, ensuring consistent signal integrity and a simpler, more reliable hardware design.
This module automatically handles voltage translation in both directions and preserves standard I²C features such as clock stretching, arbitration, and timing accuracy. Since it uses an open-drain architecture, it remains compatible with most I2C devices. Once powered and enabled, the PCA9306 starts working immediately without any software configuration.
What You’ll Learn from This Project
- Understanding the PCA9306 pinout and working principle
- How to interface the PCA9306 with Arduino Uno
- Reading data from a 3.3V I²C sensor using a 5V Arduino
- Correct wiring practices for reliable I²C communication
- Common issues and troubleshooting tips for I²C level shifting
Understanding the PCA9306 Level Shifter Module
The PCA9306 manages two separate I2C voltage domains:
- VREF1 defines the low-voltage side (typically 3.3V)
- VREF2 defines the high-voltage side (typically 5V)
Each side has its own SDA and SCL pins, allowing seamless bidirectional signal translation. A common ground between both devices is mandatory, as it provides a shared reference point for voltage levels. The EN (Enable) pin must be driven HIGH (usually tied to VREF2) to activate the module.
Most PCA9306 breakout boards include pull-up resistors on the low-voltage side, while the high-voltage side typically relies on the host controller’s pull-ups.
PCA9306 Pin Description
- VREF1 – Low-voltage reference (3.3V)
- VREF2 – High-voltage reference (5V)
- SCL1 / SDA1 – I²C lines for 3.3V devices
- SCL2 / SDA2 – I²C lines for 5V devices (Arduino A5/A4)
- GND – Common ground
- EN – Enable pin (must be HIGH)
Components Required
- Arduino Uno
- PCA9306 Level Shifter
- BMP180 Sensor
- Breadboard
- Jumper Wires
- USB Cable
Wiring the PCA9306 with Arduino Uno
To interface a 3.3V BMP180 sensor with a 5V Arduino:
- Connect VREF1 → 3.3V
- Connect VREF2 → 5V
- Connect SDA2 → A4, SCL2 → A5
- Connect SDA1 / SCL1 → BMP180
- Tie all GND pins together
- Pull EN HIGH
Once wired, no special configuration is required for the PCA9306.
Real-World Applications of PCA9306
- Connecting 3.3V sensors to 5V microcontrollers
- Interfacing EEPROMs across voltage domains
- Multi-board embedded systems
- Backplane or modular I²C designs
- Legacy hardware integration
In this project, we successfully interfaced the PCA9306 logic level shifter with an Arduino Uno to communicate with a 3.3V BMP180 pressure sensor. By using proper voltage references, correct wiring, and a shared ground, we achieved stable I2C communication without modifying the software.
The PCA9306 proves to be a reliable and efficient solution for bidirectional I²C voltage translation, especially in mixed-voltage embedded systems.
