I2C Character Display

This Rust embedded-hal-based library is a simple way to control a HD44780 compatible character display with an "I2C backpack" interface in an embedded, no_std environment. A number of I2C backpack interfaces are supported:

• Adafruit I2C/SPI LCD Backpack - This is a simple I2C backpack that can be used with either I2C or SPI. It is available from Adafruit and other retailers. This library only supports the I2C interface.
• PCF8574-based I2C adapter - These adapters are ubiquitous on eBay and AliExpress and have no clear branding. The most common pin wiring uses 4 data pins and 3 control pins. Most models have the display 4-bit data pins connected to P4-P7 of the PCF8574. This library supports that configuration, though it would be straightforward to add support for other configurations.

Key features include:

• Convenient high-level API for controlling the display
• Support for custom characters
• Backlight control
• core::fmt::Write implementation for easy use with the write! macro
• Compatible with the embedded-hal traits v1.0 and later

Usage

Add this to your Cargo.toml:

[dependencies]
i2c-character-display = { version = "0.1", features = ["defmt"] }

The features = ["defmt"] line is optional and enables the defmt feature, which allows the library's errors to be used with the defmt logging framework. Then select the appropriate adapter for your display:

use i2c_character_display::{AdafruitLCDBackpack, CharacterDisplayPCF8574T, LcdDisplayType};
use embedded_hal::delay::DelayMs;
use embedded_hal::i2c::I2c;

// board setup
let i2c = ...; // I2C peripheral
let delay = ...; // DelayMs implementation

// It is recommended that the `i2c` object be wrapped in an `embedded_hal_bus::i2c::CriticalSectionDevice` so that it can be shared between
// multiple peripherals.

// Adafruit backpack
let mut lcd = AdafruitLCDBackpack::new(i2c, LcdDisplayType::Lcd16x2, delay);
// PCF8574T adapter
let mut lcd = CharacterDisplayPCF8574T::new(i2c, LcdDisplayType::Lcd16x2, delay);

When creating the display object, you can choose the display type from the LcdDisplayType enum. The display type should match the physical display you are using. This display type configures the number of rows and columns, and the internal row offsets for the display.

Initialize the display:

if let Err(e) = lcd.init() {
   panic!("Error initializing LCD: {}", e);
}

Use the display:

// set up the display
lcd.backlight(true)?.clear()?.home()?;
// print a message
lcd.print("Hello, world!")?;
// can also use the `core::fmt::write!` macro
use core::fmt::Write;

write!(lcd, "Hello, world!")?;

The various methods for controlling the LCD are also available. Each returns a Result that wraps the display object in Ok(), allowing for easy chaining of commands. For example:

lcd.backlight(true)?.clear()?.home()?.print("Hello, world!")?;

License

Licensed under the MIT license.