Pololu Isolated USB-to-I²C Adapter

This USB-to-I²C adaptor enables a PC or other USB host to act as the controller on an I²C bus, reading and writing data from I²C target devices connected to the bus. It supports clock stretching and I²C clock speeds in excess of 1 MHz.

AUD$ 16.95

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Description

Overview

Pololu Isolated USB-to-I²C Adapter, bottom view with US quarter for size reference.

This USB-to-I²C adaptor functions as a bridge between I²C devices and a PC or other USB host, enabling the USB host to serve as an I²C controller and communicate with target devices on the I²C bus. It supports bidirectional communication with clock stretching and I²C clock speeds beyond 1000 kHz.

The adaptor provides full galvanic isolation between the USB and I²C sides, which prevents unexpected current flow between the USB host and the I²C bus and protects the USB host from damaging voltages on the I²C bus (the adaptor would be damaged under such conditions, but those voltages would not be able to propagate through to the USB side).

The module features a USB Type-C connector. On the USB side, the adaptor acts as a virtual serial port (CDC ACM), so it is recognised by major operating systems (e.g. Windows 10 and later, Linux, and macOS) without requiring any driver installation. This means the adaptor can be used with any programming environment that allows writing and reading binary data from a serial port (see the user’s guide for documentation on the communication protocol). We provide a Python library for the adaptor to make it easy to get started in Python, and the firmware for the adaptor’s STM32C071G8 microcontroller is open source for those who want to understand better how it works or customise the behaviour.

The I²C side features a JST PH-style 4-pin connector that is compatible with Sparkfun’s Qwiic and Adafruit’s STEMMA QT. It also brings the four I²C pins out to 0.1″-pitch through-holes that are compatible with standard 0.1″ male headers and female headers.

Note: This adaptor does not deliver USB power to the I²C side and instead requires target power to be supplied separately; an alternative adaptor version is available that delivers isolated power to the target.

Connections

Pololu Isolated USB-to-I²C Adapter pinout and LEDs.

Pin	Cable colour	Function
1	Black	I²C ground (GND); this pin is NOT connected to USB GND
2	Red	I²C input voltage (VCC); user must supply 2.25 V to 5.5 V across this pin and GND
3	Blue	I²C data line (SDA)
4	Yellow	I²C clock line (SCL)