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#![no_std]
#![allow(clippy::needless_doctest_main)]
#![deny(warnings)]
//! Library that implements low-level protocol to the [Hitachi HD44780][1]-compatible LCD device.
//!
//! Provides high-level API to the [Hitachi HD44780][1]-compatible LCD device. Uses 4-bit mode
//! by default (only uses 4 data pins) plus two control pins (R/S and EN). R/W pin 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
//! ```rust,no_run
//! use core::fmt::Write; // for write!
//! use lcd::*;
//!
//! // implement HAL...
//! struct HW {
//! // any data needed to access low-level peripherals
//! }
//!
//! // implement `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 `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
//! }
//! }
//!
//! # fn main() {
//!
//! // 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.entry_mode(EntryModeDirection::EntryRight, EntryModeShift::NoShift);
//!
//! // print something
//! write!(&mut lcd, "Hello, my number today is {: >4}", 42).unwrap();
//!
//! # }
//! ```
//!
//! See [`lcd-example-bluepill`](https://github.com/idubrov/lcd-example-bluepill) for the working example
//! for the [Blue Pill](http://wiki.stm32duino.com/index.php?title=Blue_Pill) development board.
//!
//! [1]: https://en.wikipedia.org/wiki/Hitachi_HD44780_LCD_controller
#[derive(Copy, Clone, Debug)]
pub enum FunctionMode {
/// Send data 4 bits at the time
Bit4 = 0x00,
/// Send data 8 bits at the time
Bit8 = 0x10,
}
#[derive(Copy, Clone, Debug)]
pub enum FunctionDots {
Dots5x8 = 0x00,
Dots5x10 = 0x04,
}
#[derive(Copy, Clone, Debug)]
pub enum FunctionLine {
Line1 = 0x00,
Line2 = 0x08,
}
#[derive(Copy, Clone, Debug)]
pub enum DisplayBlink {
BlinkOff = 0x00,
BlinkOn = 0x01,
}
#[derive(Copy, Clone, Debug)]
pub enum DisplayCursor {
CursorOff = 0x00,
CursorOn = 0x02,
}
#[derive(Copy, Clone, Debug)]
pub enum DisplayMode {
DisplayOff = 0x00,
DisplayOn = 0x04,
}
#[derive(Copy, Clone, Debug)]
pub enum Direction {
Left = 0x00,
Right = 0x04,
}
#[derive(Copy, Clone, Debug)]
pub enum Scroll {
CursorMove = 0x00,
DisplayMove = 0x08,
}
#[derive(Copy, Clone, Debug)]
pub enum EntryModeDirection {
EntryLeft = 0x00,
EntryRight = 0x02,
}
#[derive(Copy, Clone, Debug)]
pub enum EntryModeShift {
NoShift = 0x00,
Shift = 0x01,
}
#[derive(Copy, Clone, Debug)]
pub enum Command {
ClearDisplay = 0x01,
ReturnHome = 0x02,
EntryModeSet = 0x04,
DisplayControl = 0x08,
CursorShift = 0x10,
FunctionSet = 0x20,
SetCGRamAddr = 0x40,
SetDDRamAddr = 0x80,
}
pub trait Delay {
/// Delay for given amount of time (in microseconds).
fn delay_us(&mut self, delay_usec: u32);
}
trait InternalHardware {
fn rs(&self, bit: bool);
fn enable(&self, bit: bool);
fn data(&self, data: u8);
fn wait_address(&self) {}
fn mode(&self) -> FunctionMode;
fn rw(&self, bit: bool);
fn read_data(&self) -> u8;
}
pub trait Hardware {
fn rs(&mut self, bit: bool);
fn enable(&mut self, bit: bool);
fn data(&mut self, data: u8);
/// Address set up time is 40ns minimum (tAS)
/// This function should be overridden in case processor is too fast for 40ns to pass.
fn wait_address(&mut self) {}
/// Override to pick 8-bit mode (4-bit mode by default)
fn mode(&self) -> FunctionMode {
FunctionMode::Bit4
}
/// If this implementation can read from the data port. Default is `false`. If `true` is
/// returned, both `rw` and `read_data` need to be implemented.
fn can_read(&self) -> bool {
false
}
/// Set R/W flag.
///
/// Implementation should re-configure GPIO for input _before_ setting R/W pin to `true`
/// and configure GPIO for output _after_ setting R/W to `false`.
///
/// Note that LCD driver typically uses 5V, so input should be tolerant to 5V when using busy
/// flag.
///
/// Default implementation will panic.
fn rw(&mut self, _bit: bool) {
unimplemented!()
}
/// Read data from the data pins of the LCD (D0-D7 in 8-bit mode and D4-D7 in 4-bit mode)
///
/// Default implementation will panic.
fn read_data(&mut self) -> u8 {
unimplemented!()
}
/// Send data to the device.
///
/// This is mainly for LCDs attached via I2C / SMBUS where it's important to make changes to
/// data and control lines at the same time.
///
/// If control and data lines are directly attached, there's no need to implement this method.
fn apply(&mut self) {}
}
/// Object implementing HD44780 protocol. Stateless (could be created as many times as needed).
pub struct Display<HW: Hardware + Delay> {
hw: HW,
}
trait WaitReady {
fn wait_ready(&self, delay: u32);
}
impl<HW: Hardware + Delay> core::fmt::Write for Display<HW> {
fn write_str(&mut self, s: &str) -> core::fmt::Result {
self.print(s);
Ok(())
}
}
impl<HW: Hardware + Delay> Display<HW> {
pub fn new(hw: HW) -> Display<HW> {
Display { hw }
}
/// Initialize LCD display. Sets an equivalent of the following setup:
///
/// ```rust,no_run
/// # use lcd::*;
/// # struct HW {}
/// # impl Hardware for HW {
/// # fn rs(&mut self, bit: bool) { }
/// # fn enable(&mut self, bit: bool) { }
/// # fn data(&mut self, data: u8) { }
/// # }
/// # impl Delay for HW {
/// # fn delay_us(&mut self, delay_usec: u32) { }
/// # }
/// # let hw = HW {};
/// # let mut lcd = Display::new(hw);
/// lcd.display(DisplayMode::DisplayOff, DisplayCursor::CursorOff, DisplayBlink::BlinkOff);
/// lcd.clear();
/// lcd.entry_mode(EntryModeDirection::EntryRight, EntryModeShift::NoShift);
/// ```
#[inline(never)]
pub fn init(&mut self, line: FunctionLine, dots: FunctionDots) {
let mode = self.hw.mode();
self.hw.rs(false);
self.hw.apply();
self.hw.wait_address();
match mode {
FunctionMode::Bit8 => {
// Run initialization procedure for the display (8-bit mode).
// Set to 8-bit mode, 2 line, 5x10 font
// Display off, clear, entry mode set
self.send_data(
(Command::FunctionSet as u8)
| (FunctionMode::Bit8 as u8)
| (FunctionLine::Line2 as u8)
| (FunctionDots::Dots5x10 as u8),
); // Send command for the first time
self.hw.delay_us(4500); // Wait for more than 4.1ms
self.pulse_enable(); // Repeat for the second time
self.hw.delay_us(150); // Wait for more than 100us
self.pulse_enable(); // Repeat for the third time
self.wait_ready_default();
}
FunctionMode::Bit4 => {
// Run initialization procedure for the display (4-bit mode).
self.send_data(((Command::FunctionSet as u8) | (FunctionMode::Bit8 as u8)) >> 4);
self.hw.delay_us(4500); // Wait for more than 4.1ms
self.pulse_enable(); // Repeat for the second time
self.hw.delay_us(150); // Wait for more than 100us
self.pulse_enable(); // Repeat for the third time
self.wait_ready_default(); // Wait fo FunctionSet to finish
// Now we switch to 4-bit mode
self.send_data(((Command::FunctionSet as u8) | (FunctionMode::Bit4 as u8)) >> 4);
self.wait_ready_default(); // Wait for FunctionSet to finish
}
}
// Finally, set # lines, font size
self.command((Command::FunctionSet as u8) | (mode as u8) | (line as u8) | (dots as u8));
// Now display should be properly initialized, we can check BF now
// Though if we are not checking BF, waiting time is longer
self.display(
DisplayMode::DisplayOff,
DisplayCursor::CursorOff,
DisplayBlink::BlinkOff,
);
self.clear();
self.entry_mode(EntryModeDirection::EntryRight, EntryModeShift::NoShift);
}
/// Clears display and returns cursor to the home position (address 0).
pub fn clear(&mut self) -> &Self {
self.command(Command::ClearDisplay as u8);
// This command could take as long as 1.52ms to execute
self.wait_ready(2000);
self
}
/// Returns cursor to home position. Also returns display being shifted to the original position.
/// DDRAM content remains unchanged.
pub fn home(&mut self) -> &Self {
self.command(Command::ReturnHome as u8);
// This command could take as long as 1.52ms to execute
self.wait_ready(2000);
self
}
/// Sets cursor move direction (`entry`); specifies to shift the display (`scroll`).
/// These operations are performed during data read/write.
pub fn entry_mode(&mut self, dir: EntryModeDirection, scroll: EntryModeShift) -> &Self {
self.command((Command::EntryModeSet as u8) | (dir as u8) | (scroll as u8))
}
/// Sets on/off of all display (`display`), cursor on/off (`cursor`), and blink of cursor
/// position character (`blink`).
pub fn display(
&mut self,
display: DisplayMode,
cursor: DisplayCursor,
blink: DisplayBlink,
) -> &Self {
self.command(
(Command::DisplayControl as u8) | (display as u8) | (cursor as u8) | (blink as u8),
)
}
/// Sets display-shift, direction (`dir`). DDRAM content remains unchanged.
pub fn scroll(&mut self, dir: Direction) -> &Self {
self.command((Command::CursorShift as u8) | (Scroll::DisplayMove as u8) | (dir as u8))
}
/// Sets cursor-shift, direction (`dir`). DDRAM content remains unchanged.
pub fn cursor(&mut self, dir: Direction) -> &Self {
self.command((Command::CursorShift as u8) | (Scroll::CursorMove as u8) | (dir as u8))
}
/// Sets the cursor position to the given row (`row`) and column (`col`).
pub fn position(&mut self, col: u8, row: u8) {
let offset = match row {
1 => 0x40,
2 => 0x14,
3 => 0x54,
_ => 0,
};
self.command((Command::SetDDRamAddr as u8) | (col + offset));
}
/// Print given string (`str`) on the LCD screen.
pub fn print(&mut self, str: &str) -> &Self {
for c in str.as_bytes() {
self.write(*c);
}
self
}
/// Write given character (given as `data` of type `u8`) on the LCD screen.
#[inline(never)]
pub fn write(&mut self, data: u8) -> &Self {
self.hw.rs(true);
self.hw.apply();
self.hw.wait_address(); // tAS
self.send(data);
self.wait_ready_default();
// It takes 4us more (tADD) to update address counter
self.hw.delay_us(5);
self
}
/// Upload character image at given location. Only locations 0-7 are supported (panics otherwise).
/// Each character is represented by an array of 8 bytes, each byte being a row.
/// Only 5 bits are used from each byte (representing columns).
#[inline(never)]
pub fn upload_character(&mut self, location: u8, map: [u8; 8]) -> &Self {
assert!(location <= 7);
// Only 8 locations are available
self.command((Command::SetCGRamAddr as u8) | ((location & 0x7) << 3));
for item in map.iter().take(8) {
self.write(*item);
}
self
}
#[inline(never)]
fn command(&mut self, cmd: u8) -> &Self {
self.hw.rs(false);
self.hw.apply();
self.hw.wait_address(); // tAS
self.send(cmd);
self.wait_ready_default();
self
}
// Typical command wait time is 37us
fn wait_ready_default(&mut self) {
self.wait_ready(50);
}
#[inline(never)]
fn pulse_enable(&mut self) {
self.hw.enable(true);
self.hw.apply();
self.hw.delay_us(1); // minimum delay is 450 ns
self.hw.enable(false);
self.hw.apply();
}
#[inline(never)]
fn send(&mut self, data: u8) {
match self.hw.mode() {
FunctionMode::Bit8 => {
self.send_data(data);
}
FunctionMode::Bit4 => {
self.send_data(data >> 4);
self.send_data(data & 0xf);
}
}
}
#[inline(never)]
fn send_data(&mut self, data: u8) {
self.hw.data(data);
self.hw.apply();
self.pulse_enable();
}
/// Function to wait until HD44780 is ready.
#[inline(never)]
fn wait_ready(&mut self, delay: u32) {
if self.hw.can_read() {
self.hw.rs(false);
// Read mode
self.hw.rw(true);
self.hw.apply();
self.hw.wait_address(); // tAS
while self.receive() & 0b1000_0000 != 0 {}
// tAH is 10ns, which is less than one cycle. So we don't have to wait.
// Back to write mode
self.hw.rw(false);
self.hw.apply();
} else {
// Cannot read "ready" flag, so do a delay.
self.hw.delay_us(delay);
}
}
#[inline(never)]
fn receive_data(&mut self) -> u8 {
self.hw.enable(true);
self.hw.apply();
self.hw.delay_us(1);
let data = self.hw.read_data();
self.hw.delay_us(1);
self.hw.enable(false);
self.hw.apply();
data
}
fn receive(&mut self) -> u8 {
match self.hw.mode() {
FunctionMode::Bit8 => self.receive_data(),
FunctionMode::Bit4 => (self.receive_data() << 4) | (self.receive_data() & 0xf),
}
}
/// Unwrap HAL back from the driver.
pub fn unwrap(self) -> HW {
self.hw
}
}