Use generics for rows and columns

README.md

@@ -3,6 +3,9 @@
 Driver to write characters to LCD displays with a LM1602 connected via i2c like [this one] with
 16x2 characters. It requires a I2C instance implementing [`embedded_hal::blocking::i2c::Write`]
 and a instance to delay execution with [`embedded_hal::blocking::delay::DelayMs`].
+Other LCD sizes are supported, up to displays with 20x4 characters. Everything that uses a
+HD44780U or comparable controller and is connected via i2c should work.
+Like [this]
 
 Usage:
 ```
@@ -20,10 +23,9 @@ let mut i2c = arduino_hal::I2c::new(
 );
 let mut delay = arduino_hal::Delay::new();
 
-let mut lcd = lcd_lcm1602_i2c::Lcd::new(&mut i2c, &mut delay)
+let mut lcd = lcd_lcm1602_i2c::LCD16x2::new(&mut i2c, &mut delay)
     .address(LCD_ADDRESS)
-    .cursor_on(false) // no visible cursos
-    .rows(2) // two rows
+    .cursor_on(false) // no visible cursor
     .init().unwrap();
 ```
 
@@ -34,4 +36,4 @@ There is a similar crate [lcd_1602_i2c] but that did not work with [this display
 [this one]: https://funduinoshop.com/elektronische-module/displays/lcd/16x02-i2c-lcd-modul-hintergrundbeleuchtung-blau
 [lcd address]: https://www.ardumotive.com/i2clcden.html
 [lcd_1602_i2c]: https://crates.io/crates/lcd_1602_i2c
-
+[this]: https://www.az-delivery.de/en/products/hd44780-2004-lcd-display-bundle-4x20-zeichen-mit-i2c-schnittstelle

src/async_lcd.rs

@@ -2,49 +2,50 @@ use embedded_hal_async::{delay::DelayNs, i2c::I2c};
 
 use crate::{
     Backlight, BitMode, Commands, CursorMoveDir, DisplayControl, DisplayShift, Font, Mode,
+    OFFSETS_16X4, OFFSETS_NORMAL,
 };
 
 /// API to write to the LCD.
-pub struct Lcd<'a, I, D>
+pub struct Lcd<'a, const ROWS: u8, const COLUMNS: u8, I, D>
 where
     I: I2c,
     D: DelayNs,
 {
     i2c: &'a mut I,
     address: u8,
-    rows: u8,
     delay: &'a mut D,
     backlight_state: Backlight,
     cursor_on: bool,
     cursor_blink: bool,
     font_mode: Font,
 }
 
-impl<'a, I, D> Lcd<'a, I, D>
+impl<'a, const ROWS: u8, const COLUMNS: u8, I, D> Lcd<'a, ROWS, COLUMNS, I, D>
 where
     I: I2c,
     D: DelayNs,
 {
     /// Create new instance with only the I2C and delay instance.
     pub fn new(i2c: &'a mut I, delay: &'a mut D) -> Self {
+        const {
+            assert!(ROWS > 0, "ROWS needs to be larger than zero!");
+            assert!(COLUMNS > 0, "COLUMNS needs to be larger than zero!");
+            assert!(
+                ROWS < 5,
+                "This library only supports LCDs with up to four rows!"
+            ); // Because we don't have offsets for more than four rows
+        };
         Self {
             i2c,
             delay,
             backlight_state: Backlight::On,
             address: 0,
-            rows: 0,
             cursor_blink: false,
             cursor_on: false,
             font_mode: Font::Font5x8,
         }
     }
 
-    /// Zero based number of rows.
-    pub fn with_rows(mut self, rows: u8) -> Self {
-        self.rows = rows;
-        self
-    }
-
     /// Set I2C address, see [lcd address].
     ///
     /// [lcd address]: https://badboi.dev/rust,/microcontrollers/2020/11/09/i2c-hello-world.html
@@ -173,7 +174,16 @@ where
 
     /// Set the cursor to (rows, col). Coordinates are zero-based.
     pub async fn set_cursor(&mut self, row: u8, col: u8) -> Result<(), I::Error> {
-        let shift: u8 = row * 0x40 + col;
+        assert!(row < ROWS, "Row needs to be smaller than ROWS");
+        assert!(col < COLUMNS, "col needs to be smaller than COLUMNS");
+
+        let offset = if ROWS == 4 && COLUMNS == 16 {
+            OFFSETS_16X4[row as usize]
+        } else {
+            OFFSETS_NORMAL[row as usize]
+        };
+
+        let shift: u8 = col + offset;
         self.command(Mode::DDRAMAddr as u8 | shift).await
     }
 
@@ -208,7 +218,10 @@ where
     /// Recomputes function set and updates the lcd
     async fn update_function_set(&mut self) -> Result<(), I::Error> {
         // Function set command
-        let lines = if self.rows == 0 { 0x00 } else { 0x08 };
+        let lines = match ROWS {
+            1 => 0x00,
+            _ => 0x08,
+        };
         self.command(
             Mode::FunctionSet as u8 | self.font_mode as u8 | lines, // Two line display
         )

src/lib.rs

@@ -2,6 +2,8 @@
 //! Driver to write characters to LCD displays with a LM1602 connected via i2c like [this one] with
 //! 16x2 characters. It requires a I2C instance implementing [`embedded_hal::blocking::i2c::Write`]
 //! and a instance to delay execution with [`embedded_hal::blocking::delay::DelayMs`].
+//! Other LCD sizes are supported, up to displays with 20x4 characters. Everything that uses a
+//! HD44780U or comparable controller and is connected via i2c should work
 //!
 //! Usage:
 //! ```
@@ -19,10 +21,9 @@
 //! );
 //! let mut delay = arduino_hal::Delay::new();
 //!
-//! let mut lcd = lcd_lcm1602_i2c::Lcd::new(&mut i2c, &mut delay)
+//! let mut lcd = lcd_lcm1602_i2c::LCD16x2::new(&mut i2c, &mut delay)
 //!     .with_address(LCD_ADDRESS)
-//!     .with_cursor_on(false) // no visible cursos
-//!     .with_rows(2) // two rows
+//!     .with_cursor_on(false) // no visible cursor
 //!     .init().unwrap();
 //! ```
 //!
@@ -31,6 +32,8 @@
 //! [this one]: https://funduinoshop.com/elektronische-module/displays/lcd/16x02-i2c-lcd-modul-hintergrundbeleuchtung-blau
 //! [lcd address]: https://www.ardumotive.com/i2clcden.html
 
+use sync_lcd::Lcd;
+
 #[cfg(feature = "async")]
 pub mod async_lcd;
 pub mod sync_lcd;
@@ -93,3 +96,18 @@ pub enum DisplayShift {
     Decrement = 0x00,
     Increment = 0x01,
 }
+
+// offsets taken from the NewLiquidCrystal library
+const OFFSETS_NORMAL: [u8; 4] = [0x00, 0x40, 0x14, 0x54]; // For regular LCDs
+const OFFSETS_16X4: [u8; 4] = [0x00, 0x40, 0x10, 0x50]; // For 16x4 LCDs
+
+pub type LCD16x2<'a, I, D> = Lcd<'a, 2, 16, I, D>;
+pub type LCD16x4<'a, I, D> = Lcd<'a, 4, 16, I, D>;
+pub type LCD20x4<'a, I, D> = Lcd<'a, 4, 20, I, D>;
+
+#[cfg(feature = "async")]
+pub type AsyncLCD16x2<'a, I, D> = async_lcd::Lcd<'a, 2, 16, I, D>;
+#[cfg(feature = "async")]
+pub type AsyncLCD16x4<'a, I, D> = async_lcd::Lcd<'a, 4, 16, I, D>;
+#[cfg(feature = "async")]
+pub type AsyncLCD20x4<'a, I, D> = async_lcd::Lcd<'a, 4, 20, I, D>;

src/sync_lcd.rs

@@ -5,49 +5,50 @@ use ufmt_write::uWrite;
 
 use crate::{
     Backlight, BitMode, Commands, CursorMoveDir, DisplayControl, DisplayShift, Font, Mode,
+    OFFSETS_16X4, OFFSETS_NORMAL,
 };
 
 /// API to write to the LCD.
-pub struct Lcd<'a, I, D>
+pub struct Lcd<'a, const ROWS: u8, const COLUMNS: u8, I, D>
 where
     I: I2c,
     D: DelayNs,
 {
     i2c: &'a mut I,
     address: u8,
-    rows: u8,
     delay: &'a mut D,
     backlight_state: Backlight,
     cursor_on: bool,
     cursor_blink: bool,
     font_mode: Font,
 }
 
-impl<'a, I, D> Lcd<'a, I, D>
+impl<'a, const ROWS: u8, const COLUMNS: u8, I, D> Lcd<'a, ROWS, COLUMNS, I, D>
 where
     I: I2c,
     D: DelayNs,
 {
     /// Create new instance with only the I2C and delay instance.
     pub fn new(i2c: &'a mut I, delay: &'a mut D) -> Self {
+        const {
+            assert!(ROWS > 0, "ROWS needs to be larger than zero!");
+            assert!(COLUMNS > 0, "COLUMNS needs to be larger than zero!");
+            assert!(
+                ROWS < 5,
+                "This library only supports LCDs with up to four rows!"
+            ); // Because we don't have offsets for more than four rows
+        };
         Self {
             i2c,
             delay,
             backlight_state: Backlight::On,
             address: 0,
-            rows: 0,
             cursor_blink: false,
             cursor_on: false,
             font_mode: Font::Font5x8,
         }
     }
 
-    /// Zero based number of rows.
-    pub fn with_rows(mut self, rows: u8) -> Self {
-        self.rows = rows;
-        self
-    }
-
     /// Set I2C address, see [lcd address].
     ///
     /// [lcd address]: https://badboi.dev/rust,/microcontrollers/2020/11/09/i2c-hello-world.html
@@ -169,7 +170,16 @@ where
 
     /// Set the cursor to (rows, col). Coordinates are zero-based.
     pub fn set_cursor(&mut self, row: u8, col: u8) -> Result<(), I::Error> {
-        let shift: u8 = row * 0x40 + col;
+        assert!(row < ROWS, "Row needs to be smaller than ROWS");
+        assert!(col < COLUMNS, "col needs to be smaller than COLUMNS");
+
+        let offset = if ROWS == 4 && COLUMNS == 16 {
+            OFFSETS_16X4[row as usize]
+        } else {
+            OFFSETS_NORMAL[row as usize]
+        };
+
+        let shift: u8 = col + offset;
         self.command(Mode::DDRAMAddr as u8 | shift)
     }
 
@@ -203,7 +213,10 @@ where
     /// Recomputes function set and updates the lcd
     fn update_function_set(&mut self) -> Result<(), I::Error> {
         // Function set command
-        let lines = if self.rows == 0 { 0x00 } else { 0x08 };
+        let lines = match ROWS {
+            1 => 0x00,
+            _ => 0x08,
+        };
         self.command(
             Mode::FunctionSet as u8 | self.font_mode as u8 | lines, // Two line display
         )
@@ -236,7 +249,7 @@ where
     }
 }
 
-impl<'a, I, D> uWrite for Lcd<'a, I, D>
+impl<'a, const ROWS: u8, const COLUMNS: u8, I, D> uWrite for Lcd<'a, ROWS, COLUMNS, I, D>
 where
     I: I2c,
     D: DelayNs,