USB I2C

USB-I2C bridge

USB to I2C bridge implemented on ESP32-C3FN4 MCU.

Features

• Serial to I2C interface
• Alert line
• 3.3V, 5V power supply
• Simple serial protocol
• Implemented in MicroPython
• Designed in KiCAD

Connectors

All connectors have the same pin-out as follows.

1. GND
2. SCL
3. SDA
4. +3.3 V
5. +5V
6. ALERT (IRQ)

Binding

For Node.js there is a library i2c-js published on NPM as @burgrp/i2c.

USB protocol

• VID: 303A
• PID: 1001

The bridge is controlled through serial port by simple text protocol:

• S scans bus for devices, replies Saddr1,addr2,addr3,...
• R,addr,len reads data from device, replies R,hex_data
• W,addr,hex_data writes data to device, replies W,acked_count
• A gets alert line status, replies AT (true) or AF (false).

Addresses are always expressed in 7bit format, therefore without R/W bit.

Example

By commands S, R,79,2, A we can scan the bus, read temperature from LM75A sensor found on address 79 and check the alert line:

> miniterm /dev/ttyACM0 115200 --raw
--- Miniterm on /dev/ttyACM0  115200,8,N,1 ---
--- Quit: Ctrl+] | Menu: Ctrl+T | Help: Ctrl+T followed by Ctrl+H ---
S
S79
R,79,2
R1A40
A
AF

License

This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.