lcd

Library that implements low-level protocol to the Hitachi HD44780-compatible LCD device.

Provides high-level API to the Hitachi HD44780-compatible LCD device. Uses 4-bit mode by default (only uses 4 data pins) plus two control pins (R/S and EN). Using the R/W pin is optional; when Hardware::can_read() returns false (the default implementation), it is not used and should be wired for "write" (low-level, 0).

The implementation is completely stateless. Client is free to reuse the same Display object or to create one every time access to LCD is required.

Display also implements core::fmt::Write trait, so it could be used as a target of write! macro.

This library does not depend on std crate and could be used in bare metal embedded development.

Examples

use core::fmt::Write; // for write!
use lcd::*;

// implement HAL...
struct HW {
    // any data needed to access low-level peripherals
}

// Implement the `Hardware` trait to give access to LCD pins
impl Hardware for HW {
    fn rs(&mut self, bit: bool) {
        // should set R/S pin on LCD screen
    }
    fn enable(&mut self, bit: bool) {
        // should set EN pin on LCD screen
    }
    fn data(&mut self, data: u8) {
        // should set data bits to the LCD screen (only lowest 4 bits are used in 4-bit mode).
    }

    // optionally, override the following function to switch to 8-bit mode
    fn mode(&self) -> lcd::FunctionMode {
        lcd::FunctionMode::Bit8
    }

    // optionally, implement the following three functions to enable polling busy flag instead of delay
    fn can_read(&self) -> bool {
        true
    }

    fn rw(&mut self, bit: bool) {
        // configure pins for input _before_ setting R/W to 1
        // configure pins for output _after_ setting R/W to 0
    }
    fn read_data(&mut self) -> u8 {
        0 // read data from the port
    }
}

// Implement the `Delay` trait to allow library to sleep for the given amount of time
impl Delay for HW {
    fn delay_us(&mut self, delay_usec: u32) {
        // should sleep for the given amount of microseconds
    }
}

// If your hardware has a backlight, implement `Backlight` trait to control it
impl Backlight for HW {
    fn set_backlight(&mut self, enable: bool) {
        // configure pins to turn the backlight on/off.
    }
}


// create HAL and LCD instances
let hw = HW { /* ... */ };
let mut lcd = Display::new(hw);

// initialization
lcd.init(FunctionLine::Line2, FunctionDots::Dots5x8);
lcd.display(
    DisplayMode::DisplayOn,
    DisplayCursor::CursorOff,
    DisplayBlink::BlinkOff);
lcd.backlight(true); // available only if HW implements Backlight.
lcd.entry_mode(EntryModeDirection::EntryRight, EntryModeShift::NoShift);

// print something
write!(&mut lcd, "Hello, my number today is {: >4}", 42).unwrap();

See lcd-example-bluepill for the working example for the Blue Pill development board.

License

Licensed under either of

• Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.