char_lcd_rgb_i2c

A Rust library for controlling RGB1602 LCD displays connected to Raspberry Pi via MCP23017 I/O expanders.

Overview

This project is a Rust port of a Go implementation for interfacing with RGB1602 LCD displays using the MCP23017 I/O expander chip. The MCP23017 communicates with the Raspberry Pi via I2C protocol, providing additional GPIO pins to control the LCD, backlight, and RGB LED.

Key features:

• Control 16x2 character LCD displays
• Backlight control
• RGB LED control
• Support for 5 built-in buttons
• I2C interface (default address: 0x20)

Background

This library was developed for a specific RGB1602 LCD board with the following features:

• I2C Interface (Address: 0x20)
• LCD 16x2 Characters
• 5 Buttons
• 1 RGB LED
• Uses MCP23017

While similar to the Adafruit 16x2 Character LCD Plus Keypad for Raspberry Pi, this board has different backlight functionality which this library specifically addresses.

Usage

Add the library to your Cargo.toml:

[dependencies]
char_lcd_rgb_i2c = { git = "https://github.com/jyap808/char_lcd_rgb_i2c.git" }

Basic example:

use char_lcd_rgb_i2c::{CharLCDRGBI2C, LcdError};
use std::{thread::sleep, time::Duration};

fn main() -> Result<(), LcdError> {
    // Initialize a 16x2 LCD
    let mut lcd = CharLCDRGBI2C::new(16, 2)?;
    
    // Set backlight and display some text
    lcd.set_backlight(true)?;
    lcd.set_color(100, 0, 0)?;  // Red
    lcd.message("Hello, world!\nFrom Rust!")?;
    
    sleep(Duration::from_secs(2));
    
    // Change LED color to blue
    lcd.set_color(0, 0, 100)?;
    
    Ok(())
}

See the examples/lcd_demo.rs file for a more comprehensive example.

Requirements

• Raspberry Pi or compatible single-board computer
• Rust 2021 edition or newer
• rppal crate for Raspberry Pi GPIO access
• MCP23017 I/O expander
• RGB1602 LCD display

Cross-Compilation

For cross-compiling to Raspberry Pi, add this to your .cargo/config.toml:

[target.armv7-unknown-linux-gnueabihf]
linker = "armv7l-unknown-linux-gnueabihf-gcc"
# Required for NixOS
rustflags = [
  "-C", "link-arg=-Wl,-dynamic-linker=/lib/ld-linux-armhf.so.3"
]

Then build with:

cargo build --target armv7-unknown-linux-gnueabihf

Origins and Credits

This library is a Rust port created as an exercise in library development and cross-language porting. The implementation is inspired by the Adafruit CircuitPython CharLCD Library.

License

MIT License