I2C LCD Display Driver for ESP32

A robust no_std Rust driver for HD44780-based LCD displays with PCF8574 I2C backpack, designed for ESP32 microcontrollers using the esp-hal framework.

Features

• Automatic I2C Address Detection - Scans common addresses (0x27, 0x3F, 0x20, 0x38)
• Robust Initialization - Multiple retry attempts with proper timing delays
• 4-bit Mode Operation - Efficient communication with HD44780 controllers
• Backlight Control - Built-in backlight testing and control
• Error Handling - Comprehensive error reporting with LED feedback
• Built-in Testing - Self-test patterns to verify display functionality

Hardware Requirements

• ESP32 microcontroller
• 16x2 LCD display with PCF8574 I2C backpack
• Connections:
  • SDA: GPIO21
  • SCL: GPIO22
  • Status LED: GPIO2 (onboard)

Usage

Basic Setup

let i2c = I2c::new(peripherals.I2C0, I2cConfig::default().with_frequency(Rate::from_khz(10)))
    .with_sda(peripherals.GPIO21)
    .with_scl(peripherals.GPIO22);

let mut lcd = LcdI2c::new(i2c).expect("LCD initialization failed");

Display Operations

// Clear display
lcd.clear()?;

// Set cursor position (col, row)
lcd.set_cursor(0, 0)?;

// Print text
lcd.print("Hello, World!")?;

// Print at specific position
lcd.print_at(0, 1, "Line 2")?;

// Run self-test
lcd.test_display()?;

Error Indicators

The driver provides visual feedback through GPIO2 LED:

• 2 quick blinks: Startup sequence
• 1 long blink: LCD found successfully
• 3 quick blinks: Display test passed
• 5 quick blinks: Display test failed
• SOS pattern: LCD not detected or initialization failed

Technical Details

I2C Configuration

• Speed: 10kHz (slow for maximum compatibility)
• Addresses scanned: 0x27, 0x3F, 0x20, 0x38

LCD Initialization Sequence

1. Extended power-up delay (200ms)
2. Backlight test
3. Software reset sequence
4. 8-bit to 4-bit mode transition
5. Display configuration

Communication Protocol

• 4-bit mode operation
• Proper timing delays between commands
• Backlight control integrated
• RS pin control for data/command selection

Project Structure

src/
├── main.rs                 # Main application with LCD driver
└── (no additional modules)

Dependencies

• esp-hal - ESP32 hardware abstraction layer
• embedded-hal - Hardware abstraction traits

Building

cargo build --release

License

This project is designed for embedded systems use with the ESP32 (wroom32) platform.