I2C LCD Backpack Module for HD44780 Character Displays

The I2C LCD Backpack Module converts standard parallel HD44780 character displays into a streamlined two-wire I2C interface using the PCA8574 I/O expander. By driving displays using only SDA and SCL lines, it preserves vital microcontroller pins for other sensors and actuators. It is ideal for students, hobbyists, and makers building compact robotics and embedded instrumentation projects.

Two-wire I2C communication

This adapter simplifies parallel LCD connections down to two communication lines: SDA and SCL. By eliminating the need for 6 to 8 data and control pins, it frees up valuable microcontroller GPIO resources on development boards such as Arduino.

Broad HD44780 display compatibility

The module supports common character LCD sizes including LCD1601, LCD1602, LCD1604, and LCD2004 panels. Integrated contrast adjustment circuitry ensures clear text readout across different lighting environments and display models.

Onboard 8-bit GPIO expander

Powered by the PCA8574 expander, the board provides an 8-bit quasi-bidirectional I/O port over the I2C bus. This allows it to double as an auxiliary digital expander for driving extra peripherals with minimal pin overhead.

Flexible connectivity and compact footprint

Operating at a 5V supply voltage with a default I2C address of 0x20 (addressable from 0x20 to 0x27), the module includes both standard I2C/TWI and dual Gadgeteer IDC10 interfaces for quick prototyping.

Downloads & documentation

• Schematic Prints
• Remote 8-bit I/O expander DATASHEET
• Protel Schematic