HD44780 driver rework (#16370)

7 files changed, 800 insertions, 944 deletions

diff --git a/builddefs/common_features.mk b/builddefs/common_features.mk
index 08d186d656..a1793f91a5 100644
--- a/builddefs/common_features.mk
+++ b/builddefs/common_features.mk
@@ -646,8 +646,9 @@ ifeq ($(strip $(HAPTIC_ENABLE)),yes)
 endif
 
 ifeq ($(strip $(HD44780_ENABLE)), yes)
-    SRC += platforms/avr/drivers/hd44780.c
     OPT_DEFS += -DHD44780_ENABLE
+    COMMON_VPATH += $(DRIVER_PATH)/lcd
+    SRC += hd44780.c
 endif
 
 VALID_OLED_DRIVER_TYPES := SSD1306 custom
diff --git a/docs/_summary.md b/docs/_summary.md
index 250a48fe6b..249bfcd9ed 100644
--- a/docs/_summary.md
+++ b/docs/_summary.md
@@ -94,7 +94,7 @@
 
   * Hardware Features
     * Displays
-      * [HD44780 LCD Controller](feature_hd44780.md)
+      * [HD44780 LCD Driver](feature_hd44780.md)
       * [ST7565 LCD Driver](feature_st7565.md)
       * [OLED Driver](feature_oled_driver.md)
     * Lighting
diff --git a/docs/feature_hd44780.md b/docs/feature_hd44780.md
index dc476c734f..4ade640baa 100644
--- a/docs/feature_hd44780.md
+++ b/docs/feature_hd44780.md
@@ -1,57 +1,298 @@
-# HD44780 LCD Displays
-
-This is an integration of Peter Fleury's LCD library. This page will explain the basics. [For in depth documentation visit his page.](http://www.peterfleury.epizy.com/doxygen/avr-gcc-libraries/group__pfleury__lcd.html)
-
-You can enable support for HD44780 Displays by setting the `HD44780_ENABLE` flag in your keyboards `rules.mk` to yes.
-
-## Configuration
-
-You will need to configure the pins used by your display, and its number of lines and columns in your keyboard's `config.h`.
-
-
-Uncomment the section labled HD44780 and change the parameters as needed.
-````
-/*
- * HD44780 LCD Display Configuration
- */
-
-#define LCD_LINES           2     //< number of visible lines of the display
-#define LCD_DISP_LENGTH    16     //< visibles characters per line of the display
-#define LCD_IO_MODE      1            //< 0: memory mapped mode, 1: IO port mode
-#if LCD_IO_MODE
-#define LCD_PORT         PORTB        //< port for the LCD lines
-#define LCD_DATA0_PORT   LCD_PORT     //< port for 4bit data bit 0
-#define LCD_DATA1_PORT   LCD_PORT     //< port for 4bit data bit 1
-#define LCD_DATA2_PORT   LCD_PORT     //< port for 4bit data bit 2
-#define LCD_DATA3_PORT   LCD_PORT     //< port for 4bit data bit 3
-#define LCD_DATA0_PIN    4            //< pin for 4bit data bit 0
-#define LCD_DATA1_PIN    5            //< pin for 4bit data bit 1
-#define LCD_DATA2_PIN    6            //< pin for 4bit data bit 2
-#define LCD_DATA3_PIN    7            //< pin for 4bit data bit 3
-#define LCD_RS_PORT      LCD_PORT     //< port for RS line        
-#define LCD_RS_PIN       3            //< pin  for RS line        
-#define LCD_RW_PORT      LCD_PORT     //< port for RW line        
-#define LCD_RW_PIN       2            //< pin  for RW line        
-#define LCD_E_PORT       LCD_PORT     //< port for Enable line     
-#define LCD_E_PIN        1            //< pin  for Enable line    
-#endif
-````
-
-Should you need to configure other properties you can copy them from `quantum/hd44780.h` and set them in your `config.h`
+# HD44780 LCD Driver
+
+## Supported Hardware
+
+LCD modules using [HD44780U](https://www.sparkfun.com/datasheets/LCD/HD44780.pdf) IC or equivalent, communicating in 4-bit mode.
+
+|Module|Size          |Notes                            |
+|------|--------------|---------------------------------|
+|1602A |16x2, 5x8 dots|                                 |
+|2004A |20x4, 5x8 dots|Untested, not currently supported|
+
+To run these modules at 3.3V, an additional MAX660 voltage converter IC must be soldered on, along with two 10µF capacitors. See [this page](https://www.codrey.com/electronic-circuits/hack-your-16x2-lcd/) for more details.
 
 ## Usage
 
-To initialize your display, call `lcd_init()` with one of these parameters:
-````
-LCD_DISP_OFF             : display off
-LCD_DISP_ON              : display on, cursor off
-LCD_DISP_ON_CURSOR       : display on, cursor on
-LCD_DISP_ON_CURSOR_BLINK : display on, cursor on flashing
-````
-This is best done in your keyboards `matrix_init_kb` or your keymaps `matrix_init_user`.  
-It is advised to clear the display before use.  
-To do so call `lcd_clrscr()`.
+Add the following to your `rules.mk`:
+
+```make
+HD44780_ENABLE = yes
+```
+
+## Basic Configuration
+
+Add the following to your `config.h`:
+
+|Define                 |Default       |Description                                                                                          |
+|-----------------------|--------------|-----------------------------------------------------------------------------------------------------|
+|`HD44780_DATA_PINS`    |*Not defined* |(Required) An array of four GPIO pins connected to the display's D4-D7 pins, eg. `{ B1, B3, B2, B6 }`|
+|`HD44780_RS_PIN`       |*Not defined* |(Required) The GPIO connected to the display's RS pin                                                |
+|`HD44780_RW_PIN`       |*Not defined* |(Required) The GPIO connected to the display's RW pin                                                |
+|`HD44780_E_PIN`        |*Not defined* |(Required) The GPIO connected to the display's E pin                                                 |
+|`HD44780_DISPLAY_COLS` |`16`          |The number of visible characters on a single line of the display                                     |
+|`HD44780_DISPLAY_LINES`|`2`           |The number of visible lines on the display                                                           |
+|`HD44780_WRAP_LINES`   |*Not defined* |If defined, input characters will wrap to the next line                                              |
+
+## Examples
+
+### Hello World
+
+Add the following to your `keymap.c`:
+
+```c
+void keyboard_post_init_user(void) {
+    hd44780_init(true, true); // Show blinking cursor
+    hd44780_puts_P(PSTR("Hello, world!\n"));
+}
+```
+
+### Custom Character Definition
+
+Up to eight custom characters can be defined. This data is stored in the Character Generator RAM (CGRAM), and is not persistent across power cycles.
+
+This example defines the QMK Psi as the first custom character. The first 16 positions in the character set are reserved for the eight custom characters duplicated.
+
+```
+Byte |      16 8 4 2 1
+   1 | x x x ■ □ ■ □ ■
+   2 | x x x ■ □ ■ □ ■
+   3 | x x x ■ □ ■ □ ■
+   4 | x x x □ ■ ■ ■ □
+   5 | x x x □ □ ■ □ □
+   6 | x x x □ □ ■ □ □
+   7 | x x x □ □ ■ □ □
+   8 | x x x □ □ □ □ □
+```
+
+```c
+const uint8_t PROGMEM psi[8] = { 0x15, 0x15, 0x15, 0x0E, 0x04, 0x04, 0x04, 0x00 };
+
+void keyboard_post_init_user(void) {
+    hd44780_init(false, false);
+    hd44780_define_char_P(0, psi);
+    // Cursor is incremented while defining characters so must be reset
+    hd44780_home();
+    // 0x08 to avoid null terminator
+    hd44780_puts_P(PSTR("\x08 QMK Firmware"));
+}
+```
+
+## API
+
+### `void hd44780_init(bool cursor, bool blink)`
+
+Initialize the display.
+
+This function should be called only once, before any of the other functions can be called.
+
+#### Arguments
+
+ - `bool cursor`  
+   Whether to show the cursor.
+ - `bool blink`  
+   Whether to blink the cursor, if shown.
+
+---
+
+### `void hd44780_clear(void)`
+
+Clear the display.
+
+This function is called on init.
+
+---
+
+### `void hd44780_home(void)`
+
+Move the cursor to the home position.
+
+This function is called on init.
+
+---
+
+### `void hd44780_on(bool cursor, bool blink)`
+
+Turn the display on, and/or set the cursor properties.
+
+This function is called on init.
+
+#### Arguments
+
+ - `bool cursor`  
+   Whether to show the cursor.
+ - `bool blink`  
+   Whether to blink the cursor, if shown.
+
+---
+
+### `void hd44780_off(void)`
+
+Turn the display off.
+
+---
+
+### `void hd44780_set_cursor(uint8_t col, uint8_t line)`
+
+Move the cursor to the specified position on the display.
+
+#### Arguments
+
+ - `uint8_t col`  
+   The column number to move to, from 0 to 15 on 16x2 displays.
+ - `bool line`  
+   The line number to move to, either 0 or 1 on 16x2 displays.
+
+---
+
+### `void hd44780_putc(char c)`
+
+Print a character to the display. The newline character `\n` will move the cursor to the start of the next line.
+
+The exact character shown may depend on the ROM code of your particular display - refer to the datasheet for the full character set.
+
+#### Arguments
+
+ - `char c`  
+   The character to print.
+
+---
+
+### `void hd44780_puts(const char *s)`
+
+Print a string of characters to the display.
+
+#### Arguments
+
+ - `const char *s`  
+   The string to print.
+
+---
+
+### `void hd44780_puts_P(const char *s)`
+
+Print a string of characters from PROGMEM to the display.
+
+On ARM devices, this function is simply an alias of `hd44780_puts()`.
+
+#### Arguments
+
+ - `const char *s`  
+   The PROGMEM string to print (ie. `PSTR("Hello")`).
+
+---
+
+### `void hd44780_define_char(uint8_t index, uint8_t *data)`
+
+Define a custom character.
+
+#### Arguments
+
+ - `uint8_t index`  
+   The index of the custom character to define, from 0 to 7.
+ - `uint8_t *data`  
+   An array of 8 bytes containing the 5-bit row data of the character, where the first byte is the topmost row, and the least significant bit of each byte is the rightmost column.
+
+---
+
+### `void hd44780_define_char_P(uint8_t index, const uint8_t *data)`
+
+Define a custom character from PROGMEM.
+
+On ARM devices, this function is simply an alias of `hd44780_define_char()`.
+
+#### Arguments
+
+ - `uint8_t index`  
+   The index of the custom character to define, from 0 to 7.
+ - `const uint8_t *data`  
+   A PROGMEM array of 8 bytes containing the 5-bit row data of the character, where the first byte is the topmost row, and the least significant bit of each byte is the rightmost column.
+
+---
+
+### `bool hd44780_busy(void)`
+
+Indicates whether the display is currently processing, and cannot accept instructions.
+
+#### Return Value
+
+`true` if the display is busy.
+
+---
+
+### `void hd44780_write(uint8_t data, bool isData)`
+
+Write a byte to the display.
+
+#### Arguments
+
+ - `uint8_t data`  
+   The byte to send to the display.
+ - `bool isData`  
+   Whether the byte is an instruction or character data.
+
+---
+
+### `uint8_t hd44780_read(bool isData)`
+
+Read a byte from the display.
+
+#### Arguments
+
+ - `bool isData`  
+   Whether to read the current cursor position, or the character at the cursor.
+
+#### Return Value
+
+If `isData` is `true`, the returned byte will be the character at the current DDRAM address. Otherwise, it will be the current DDRAM address and the busy flag.
+
+---
+
+### `void hd44780_command(uint8_t command)`
+
+Send a command to the display. Refer to the datasheet and `hd44780.h` for the valid commands and defines.
+
+This function waits for the display to clear the busy flag before sending the command.
+
+#### Arguments
+
+ - `uint8_t command`  
+   The command to send.
+
+---
+
+### `void hd44780_data(uint8_t data)`
+
+Send a byte of data to the display.
+
+This function waits for the display to clear the busy flag before sending the data.
+
+#### Arguments
+
+ - `uint8_t data`  
+   The byte of data to send.
+
+---
+
+### `void hd44780_set_cgram_address(uint8_t address)`
+
+Set the CGRAM address.
+
+This function is used when defining custom characters.
+
+#### Arguments
+
+ - `uint8_t address`  
+   The CGRAM address to move to, from `0x00` to `0x3F`.
+
+---
+
+### `void hd44780_set_ddram_address(uint8_t address)`
+
+Set the DDRAM address.
+
+This function is used when printing characters to the display, and setting the cursor.
 
-To now print something to your Display you first call `lcd_gotoxy(column, line)`. To go to the start of the first line you would call `lcd_gotoxy(0, 0)` and then print a string with `lcd_puts("example string")`.
+#### Arguments
 
-There are more methods available to control the display. [For in depth documentation please visit the linked page.](http://www.peterfleury.epizy.com/doxygen/avr-gcc-libraries/group__pfleury__lcd.html)
+ - `uint8_t address`  
+   The DDRAM address to move to, from `0x00` to `0x7F`.
diff --git a/drivers/lcd/hd44780.c b/drivers/lcd/hd44780.c
new file mode 100644
index 0000000000..c988ebe56c
--- /dev/null
+++ b/drivers/lcd/hd44780.c
@@ -0,0 +1,284 @@
+/*
+Copyright 2022
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "hd44780.h"
+#include "gpio.h"
+#include "progmem.h"
+#include "wait.h"
+
+#ifndef HD44780_DATA_PINS
+#    error hd44780: no data pins defined!
+#endif
+
+#ifndef HD44780_RS_PIN
+#    error hd44780: no RS pin defined!
+#endif
+
+#ifndef HD44780_RW_PIN
+#    error hd44780: no R/W pin defined!
+#endif
+
+#ifndef HD44780_E_PIN
+#    error hd44780: no E pin defined!
+#endif
+
+static const pin_t data_pins[4] = HD44780_DATA_PINS;
+
+#ifndef HD44780_DISPLAY_COLS
+#    define HD44780_DISPLAY_COLS 16
+#endif
+
+#ifndef HD44780_DISPLAY_LINES
+#    define HD44780_DISPLAY_LINES 2
+#endif
+
+#ifndef HD44780_DDRAM_LINE0_ADDR
+#    define HD44780_DDRAM_LINE0_ADDR 0x00
+#endif
+#ifndef HD44780_DDRAM_LINE1_ADDR
+#    define HD44780_DDRAM_LINE1_ADDR 0x40
+#endif
+
+#define HD44780_INIT_DELAY_MS 16
+#define HD44780_ENABLE_DELAY_US 1
+
+static void hd44780_latch(void) {
+    writePinHigh(HD44780_E_PIN);
+    wait_us(HD44780_ENABLE_DELAY_US);
+    writePinLow(HD44780_E_PIN);
+}
+
+void hd44780_write(uint8_t data, bool isData) {
+    writePin(HD44780_RS_PIN, isData);
+    writePinLow(HD44780_RW_PIN);
+
+    for (int i = 0; i < 4; i++) {
+        setPinOutput(data_pins[i]);
+    }
+
+    // Write high nibble
+    for (int i = 0; i < 4; i++) {
+        writePin(data_pins[i], (data >> 4) & (1 << i));
+    }
+    hd44780_latch();
+
+    // Write low nibble
+    for (int i = 0; i < 4; i++) {
+        writePin(data_pins[i], data & (1 << i));
+    }
+    hd44780_latch();
+
+    for (int i = 0; i < 4; i++) {
+        writePinHigh(data_pins[i]);
+    }
+}
+
+uint8_t hd44780_read(bool isData) {
+    uint8_t data = 0;
+
+    writePin(HD44780_RS_PIN, isData);
+    writePinHigh(HD44780_RW_PIN);
+
+    for (int i = 0; i < 4; i++) {
+        setPinInput(data_pins[i]);
+    }
+
+    writePinHigh(HD44780_E_PIN);
+    wait_us(HD44780_ENABLE_DELAY_US);
+
+    // Read high nibble
+    for (int i = 0; i < 4; i++) {
+        data |= (readPin(data_pins[i]) << i);
+    }
+
+    data <<= 4;
+
+    writePinLow(HD44780_E_PIN);
+    wait_us(HD44780_ENABLE_DELAY_US);
+    writePinHigh(HD44780_E_PIN);
+    wait_us(HD44780_ENABLE_DELAY_US);
+
+    // Read low nibble
+    for (int i = 0; i < 4; i++) {
+        data |= (readPin(data_pins[i]) << i);
+    }
+
+    writePinLow(HD44780_E_PIN);
+
+    return data;
+}
+
+bool hd44780_busy(void) {
+    return hd44780_read(false) & HD44780_BUSY_FLAG;
+}
+
+void hd44780_command(uint8_t command) {
+    while (hd44780_busy())
+        ;
+    hd44780_write(command, false);
+}
+
+void hd44780_data(uint8_t data) {
+    while (hd44780_busy())
+        ;
+    hd44780_write(data, true);
+}
+
+void hd44780_clear(void) {
+    hd44780_command(HD44780_CMD_CLEAR_DISPLAY);
+}
+
+void hd44780_home(void) {
+    hd44780_command(HD44780_CMD_RETURN_HOME);
+}
+
+void hd44780_on(bool cursor, bool blink) {
+    if (cursor) {
+        if (blink) {
+            hd44780_command(HD44780_CMD_DISPLAY | HD44780_DISPLAY_ON | HD44780_DISPLAY_CURSOR | HD44780_DISPLAY_BLINK);
+        } else {
+            hd44780_command(HD44780_CMD_DISPLAY | HD44780_DISPLAY_ON | HD44780_DISPLAY_CURSOR);
+        }
+    } else {
+        hd44780_command(HD44780_CMD_DISPLAY | HD44780_DISPLAY_ON);
+    }
+}
+
+void hd44780_off() {
+    hd44780_command(HD44780_CMD_DISPLAY);
+}
+
+void hd44780_set_cgram_address(uint8_t address) {
+    hd44780_command(HD44780_CMD_SET_CGRAM_ADDRESS + (address & 0x3F));
+}
+
+void hd44780_set_ddram_address(uint8_t address) {
+    hd44780_command(HD44780_CMD_SET_DDRAM_ADDRESS + (address & 0x7F));
+}
+
+void hd44780_init(bool cursor, bool blink) {
+    setPinOutput(HD44780_RS_PIN);
+    setPinOutput(HD44780_RW_PIN);
+    setPinOutput(HD44780_E_PIN);
+
+    for (int i = 0; i < 4; i++) {
+        setPinOutput(data_pins[i]);
+    }
+
+    wait_ms(HD44780_INIT_DELAY_MS);
+
+    // Manually configure for 4-bit mode - can't use hd44780_command() yet
+    // HD44780U datasheet, Fig. 24 (p46)
+    writePinHigh(data_pins[0]); // Function set
+    writePinHigh(data_pins[1]); // DL = 1
+    hd44780_latch();
+    wait_ms(5);
+    // Send again
+    hd44780_latch();
+    wait_us(64);
+    // And again (?)
+    hd44780_latch();
+    wait_us(64);
+
+    writePinLow(data_pins[0]); // DL = 0
+    hd44780_latch();
+    wait_us(64);
+
+#if HD44780_DISPLAY_LINES == 1
+    hd44780_command(HD44780_CMD_FUNCTION); // 4 bit, 1 line, 5x8 dots
+#else
+    hd44780_command(HD44780_CMD_FUNCTION | HD44780_FUNCTION_2_LINES); // 4 bit, 2 lines, 5x8 dots
+#endif
+    hd44780_on(cursor, blink);
+    hd44780_clear();
+    hd44780_home();
+    hd44780_command(HD44780_CMD_ENTRY_MODE | HD44780_ENTRY_MODE_INC);
+}
+
+void hd44780_set_cursor(uint8_t col, uint8_t line) {
+    register uint8_t address = col;
+
+#if HD44780_DISPLAY_LINES == 1
+    address += HD44780_DDRAM_LINE0_ADDR;
+#elif HD44780_DISPLAY_LINES == 2
+    if (line == 0) {
+        address += HD44780_DDRAM_LINE0_ADDR;
+    } else {
+        address += HD44780_DDRAM_LINE1_ADDR;
+    }
+#endif
+
+    hd44780_set_ddram_address(address);
+}
+
+void hd44780_define_char(uint8_t index, uint8_t *data) {
+    hd44780_set_cgram_address((index & 0x7) << 3);
+    for (uint8_t i = 0; i < 8; i++) {
+        hd44780_data(data[i]);
+    }
+}
+
+void hd44780_putc(char c) {
+    while (hd44780_busy())
+        ;
+    uint8_t current_position = hd44780_read(false);
+
+    if (c == '\n') {
+        hd44780_set_cursor(0, current_position < HD44780_DDRAM_LINE1_ADDR ? 1 : 0);
+    } else {
+#if defined(HD44780_WRAP_LINES)
+#    if HD44780_DISPLAY_LINES == 1
+        if (current_position == HD44780_DDRAM_LINE0_ADDR + HD44780_DISPLAY_COLS) {
+            // Go to start of line
+            hd44780_set_cursor(0, 0);
+        }
+#    elif HD44780_DISPLAY_LINES == 2
+        if (current_position == HD44780_DDRAM_LINE0_ADDR + HD44780_DISPLAY_COLS) {
+            // Go to start of second line
+            hd44780_set_cursor(0, 1);
+        } else if (current_position == HD44780_DDRAM_LINE1_ADDR + HD44780_DISPLAY_COLS) {
+            // Go to start of first line
+            hd44780_set_cursor(0, 0);
+        }
+#    endif
+#endif
+        hd44780_data(c);
+    }
+}
+
+void hd44780_puts(const char *s) {
+    register char c;
+    while ((c = *s++)) {
+        hd44780_putc(c);
+    }
+}
+
+#if defined(__AVR__)
+void hd44780_define_char_P(uint8_t index, const uint8_t *data) {
+    hd44780_set_cgram_address(index << 3);
+    for (uint8_t i = 0; i < 8; i++) {
+        hd44780_data(pgm_read_byte(data++));
+    }
+}
+
+void hd44780_puts_P(const char *s) {
+    register char c;
+    while ((c = pgm_read_byte(s++))) {
+        hd44780_putc(c);
+    }
+}
+#endif
diff --git a/drivers/lcd/hd44780.h b/drivers/lcd/hd44780.h
new file mode 100644
index 0000000000..d4b8f9ea76
--- /dev/null
+++ b/drivers/lcd/hd44780.h
@@ -0,0 +1,220 @@
+/*
+Copyright 2022
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#pragma once
+
+#include <stdint.h>
+#include <stdbool.h>
+
+/**
+ * \defgroup hd44780
+ *
+ * HD44780 Character LCD Driver
+ * \{
+ */
+
+/*
+ * HD44780 instructions
+ * https://www.sparkfun.com/datasheets/LCD/HD44780.pdf
+ * Table 6 (p24)
+ */
+// Clear display
+#define HD44780_CMD_CLEAR_DISPLAY        0x01
+// Return home
+#define HD44780_CMD_RETURN_HOME          0x02
+// Entry mode set
+#define HD44780_CMD_ENTRY_MODE           0x04
+#define HD44780_ENTRY_MODE_INC           0x02 // I/D
+#define HD44780_ENTRY_MODE_SHIFT         0x01 // S
+// Display on/off control
+#define HD44780_CMD_DISPLAY              0x08
+#define HD44780_DISPLAY_ON               0x04 // D
+#define HD44780_DISPLAY_CURSOR           0x02 // C
+#define HD44780_DISPLAY_BLINK            0x01 // B
+// Cursor or display shift
+#define HD44780_CMD_MOVE                 0x10
+#define HD44780_MOVE_DISPLAY             0x08 // S/C
+#define HD44780_MOVE_RIGHT               0x04 // R/L
+// Function set
+#define HD44780_CMD_FUNCTION             0x20
+#define HD44780_FUNCTION_8_BIT           0x10 // DL
+#define HD44780_FUNCTION_2_LINES         0x08 // N
+#define HD44780_FUNCTION_5X10_DOTS       0x04 // F
+// Set CGRAM address
+#define HD44780_CMD_SET_CGRAM_ADDRESS    0x40
+// Set DDRAM address
+#define HD44780_CMD_SET_DDRAM_ADDRESS    0x80
+
+// Bitmask for busy flag when reading
+#define HD44780_BUSY_FLAG                0x80
+
+/**
+ * \brief Write a byte to the display.
+ *
+ * \param data The byte to send to the display.
+ * \param isData Whether the byte is an instruction or character data.
+ */
+void hd44780_write(uint8_t data, bool isData);
+
+/**
+ * \brief Read a byte from the display.
+ * 
+ * \param isData Whether to read the current cursor position, or the character at the cursor.
+ *
+ * \return If `isData` is `true`, the returned byte will be the character at the current DDRAM address. Otherwise, it will be the current DDRAM address and the busy flag.
+ */
+uint8_t hd44780_read(bool isData);
+
+/**
+ * \brief Indicates whether the display is currently processing, and cannot accept instructions.
+ *
+ * \return `true` if the display is busy.
+ */
+bool hd44780_busy(void);
+
+/**
+ * \brief Send a command to the display. Refer to the datasheet for the valid commands.
+ *
+ * This function waits for the display to clear the busy flag before sending the command.
+ * 
+ * \param command The command to send.
+ */
+void hd44780_command(uint8_t command);
+
+/**
+ * \brief Send a byte of data to the display.
+ *
+ * This function waits for the display to clear the busy flag before sending the data.
+ *
+ * \param data The byte of data to send.
+ */
+void hd44780_data(uint8_t data);
+
+/**
+ * \brief Clear the display.
+ *
+ * This function is called on init.
+ */
+void hd44780_clear(void);
+
+/**
+ * \brief Move the cursor to the home position.
+ *
+ * This function is called on init.
+ */
+void hd44780_home(void);
+
+/**
+ * \brief Turn the display on, and/or set the cursor position.
+ *
+ * This function is called on init.
+ *
+ * \param cursor Whether to show the cursor.
+ * \param blink Whether to blink the cursor, if shown.
+ */
+void hd44780_on(bool cursor, bool blink);
+
+/**
+ * \brief Turn the display off.
+ */
+void hd44780_off(void);
+
+/**
+ * \brief Set the CGRAM address.
+ *
+ * This function is used when defining custom characters.
+ *
+ * \param address The CGRAM address to move to, from `0x00` to `0x3F`.
+ */
+void hd44780_set_cgram_address(uint8_t address);
+
+/**
+ * \brief Set the DDRAM address.
+ *
+ * This function is used when printing characters to the display, and setting the cursor.
+ *
+ * \param address The DDRAM address to move to, from `0x00` to `0x7F`.
+ */
+void hd44780_set_ddram_address(uint8_t address);
+
+/**
+ * \brief Initialize the display.
+ *
+ * This function should be called only once, before any of the other functions can be called.
+ *
+ * \param cursor Whether to show the cursor.
+ * \param blink Whether to blink the cursor, if shown.
+ */
+void hd44780_init(bool cursor, bool blink);
+
+/**
+ * \brief Move the cursor to the specified position on the display.
+ * 
+ * \param col The column number to move to, from 0 to 15 on 16x2 displays.
+ * \param line The line number to move to, either 0 or 1 on 16x2 displays.
+ */
+void hd44780_set_cursor(uint8_t col, uint8_t line);
+
+/**
+ * \brief Define a custom character.
+ *
+ * \param index The index of the custom character to define, from 0 to 7.
+ * \param data An array of 8 bytes containing the 5-bit row data of the character, where the first byte is the topmost row, and the least significant bit of each byte is the rightmost column.
+ */
+void hd44780_define_char(uint8_t index, uint8_t *data);
+
+/**
+ * \brief Print a character to the display. The newline character will move the cursor to the start of the next line.
+ * 
+ * The exact character shown may depend on the ROM code of your particular display - refer to the datasheet for the full character set.
+ *
+ * \param c The character to print.
+ */
+void hd44780_putc(char c);
+
+/**
+ * \brief Print a string of characters to the display.
+ *
+ * \param s The string to print.
+ */
+void hd44780_puts(const char *s);
+
+#if defined(__AVR__) || defined(__DOXYGEN__)
+/**
+ * \brief Define a custom character from PROGMEM.
+ *
+ * On ARM devices, this function is simply an alias of hd44780_define_char().
+ *
+ * \param index The index of the custom character to define, from 0 to 7.
+ * \param data A PROGMEM array of 8 bytes containing the 5-bit row data of the character, where the first byte is the topmost row, and the least significant bit of each byte is the rightmost column.
+ */
+void hd44780_define_char_P(uint8_t index, const uint8_t *data);
+
+/**
+ * \brief Print a string of characters from PROGMEM to the display.
+ *
+ * On ARM devices, this function is simply an alias of hd44780_puts().
+ *
+ * \param s The PROGMEM string to print.
+ */
+void hd44780_puts_P(const char *s);
+#else
+#    define hd44780_define_char_P(index, data) hd44780_define_char(index, data)
+#    define hd44780_puts_P(s) hd44780_puts(s)
+#endif
+
+/** \} */
diff --git a/platforms/avr/drivers/hd44780.c b/platforms/avr/drivers/hd44780.c
deleted file mode 100644
index f15d7d0da8..0000000000
--- a/platforms/avr/drivers/hd44780.c
+++ /dev/null
@@ -1,542 +0,0 @@
-/****************************************************************************
- Title:     HD44780U LCD library
- Author:    Peter Fleury <pfleury@gmx.ch>  http://tinyurl.com/peterfleury
- License:   GNU General Public License Version 3
- File:	    $Id: lcd.c,v 1.15.2.2 2015/01/17 12:16:05 peter Exp $
- Software:  AVR-GCC 3.3
- Target:    any AVR device, memory mapped mode only for AT90S4414/8515/Mega
-
- DESCRIPTION
-       Basic routines for interfacing a HD44780U-based text lcd display
-
-       Originally based on Volker Oth's lcd library,
-       changed lcd_init(), added additional constants for lcd_command(),
-       added 4-bit I/O mode, improved and optimized code.
-
-       Library can be operated in memory mapped mode (LCD_IO_MODE=0) or in
-       4-bit IO port mode (LCD_IO_MODE=1). 8-bit IO port mode not supported.
-
-       Memory mapped mode compatible with Kanda STK200, but supports also
-       generation of R/W signal through A8 address line.
-
- USAGE
-       See the C include lcd.h file for a description of each function
-
-*****************************************************************************/
-#include <inttypes.h>
-#include <avr/io.h>
-#include <avr/pgmspace.h>
-#include <util/delay.h>
-#include "hd44780.h"
-
-/*
-** constants/macros
-*/
-#define DDR(x) (*(&x - 1)) /* address of data direction register of port x */
-#if defined(__AVR_ATmega64__) || defined(__AVR_ATmega128__)
-/* on ATmega64/128 PINF is on port 0x00 and not 0x60 */
-#    define PIN(x) (&PORTF == &(x) ? _SFR_IO8(0x00) : (*(&x - 2)))
-#else
-#    define PIN(x) (*(&x - 2)) /* address of input register of port x          */
-#endif
-
-#if LCD_IO_MODE
-#    define lcd_e_delay() _delay_us(LCD_DELAY_ENABLE_PULSE)
-#    define lcd_e_high() LCD_E_PORT |= _BV(LCD_E_PIN);
-#    define lcd_e_low() LCD_E_PORT &= ~_BV(LCD_E_PIN);
-#    define lcd_e_toggle() toggle_e()
-#    define lcd_rw_high() LCD_RW_PORT |= _BV(LCD_RW_PIN)
-#    define lcd_rw_low() LCD_RW_PORT &= ~_BV(LCD_RW_PIN)
-#    define lcd_rs_high() LCD_RS_PORT |= _BV(LCD_RS_PIN)
-#    define lcd_rs_low() LCD_RS_PORT &= ~_BV(LCD_RS_PIN)
-#endif
-
-#if LCD_IO_MODE
-#    if LCD_LINES == 1
-#        define LCD_FUNCTION_DEFAULT LCD_FUNCTION_4BIT_1LINE
-#    else
-#        define LCD_FUNCTION_DEFAULT LCD_FUNCTION_4BIT_2LINES
-#    endif
-#else
-#    if LCD_LINES == 1
-#        define LCD_FUNCTION_DEFAULT LCD_FUNCTION_8BIT_1LINE
-#    else
-#        define LCD_FUNCTION_DEFAULT LCD_FUNCTION_8BIT_2LINES
-#    endif
-#endif
-
-#if LCD_CONTROLLER_KS0073
-#    if LCD_LINES == 4
-
-#        define KS0073_EXTENDED_FUNCTION_REGISTER_ON 0x2C  /* |0|010|1100 4-bit mode, extension-bit RE = 1 */
-#        define KS0073_EXTENDED_FUNCTION_REGISTER_OFF 0x28 /* |0|010|1000 4-bit mode, extension-bit RE = 0 */
-#        define KS0073_4LINES_MODE 0x09                    /* |0|000|1001 4 lines mode */
-
-#    endif
-#endif
-
-/*
-** function prototypes
-*/
-#if LCD_IO_MODE
-static void toggle_e(void);
-#endif
-
-/*
-** local functions
-*/
-
-/*************************************************************************
-delay for a minimum of <us> microseconds
-the number of loops is calculated at compile-time from MCU clock frequency
-*************************************************************************/
-#define delay(us) _delay_us(us)
-
-#if LCD_IO_MODE
-/* toggle Enable Pin to initiate write */
-static void toggle_e(void) {
-    lcd_e_high();
-    lcd_e_delay();
-    lcd_e_low();
-}
-#endif
-
-/*************************************************************************
-Low-level function to write byte to LCD controller
-Input:    data   byte to write to LCD
-          rs     1: write data
-                 0: write instruction
-Returns:  none
-*************************************************************************/
-#if LCD_IO_MODE
-static void lcd_write(uint8_t data, uint8_t rs) {
-    unsigned char dataBits;
-
-    if (rs) { /* write data        (RS=1, RW=0) */
-        lcd_rs_high();
-    } else { /* write instruction (RS=0, RW=0) */
-        lcd_rs_low();
-    }
-    lcd_rw_low(); /* RW=0  write mode      */
-
-    if ((&LCD_DATA0_PORT == &LCD_DATA1_PORT) && (&LCD_DATA1_PORT == &LCD_DATA2_PORT) && (&LCD_DATA2_PORT == &LCD_DATA3_PORT) && (LCD_DATA0_PIN == 0) && (LCD_DATA1_PIN == 1) && (LCD_DATA2_PIN == 2) && (LCD_DATA3_PIN == 3)) {
-        /* configure data pins as output */
-        DDR(LCD_DATA0_PORT) |= 0x0F;
-
-        /* output high nibble first */
-        dataBits       = LCD_DATA0_PORT & 0xF0;
-        LCD_DATA0_PORT = dataBits | ((data >> 4) & 0x0F);
-        lcd_e_toggle();
-
-        /* output low nibble */
-        LCD_DATA0_PORT = dataBits | (data & 0x0F);
-        lcd_e_toggle();
-
-        /* all data pins high (inactive) */
-        LCD_DATA0_PORT = dataBits | 0x0F;
-    } else {
-        /* configure data pins as output */
-        DDR(LCD_DATA0_PORT) |= _BV(LCD_DATA0_PIN);
-        DDR(LCD_DATA1_PORT) |= _BV(LCD_DATA1_PIN);
-        DDR(LCD_DATA2_PORT) |= _BV(LCD_DATA2_PIN);
-        DDR(LCD_DATA3_PORT) |= _BV(LCD_DATA3_PIN);
-
-        /* output high nibble first */
-        LCD_DATA3_PORT &= ~_BV(LCD_DATA3_PIN);
-        LCD_DATA2_PORT &= ~_BV(LCD_DATA2_PIN);
-        LCD_DATA1_PORT &= ~_BV(LCD_DATA1_PIN);
-        LCD_DATA0_PORT &= ~_BV(LCD_DATA0_PIN);
-        if (data & 0x80) LCD_DATA3_PORT |= _BV(LCD_DATA3_PIN);
-        if (data & 0x40) LCD_DATA2_PORT |= _BV(LCD_DATA2_PIN);
-        if (data & 0x20) LCD_DATA1_PORT |= _BV(LCD_DATA1_PIN);
-        if (data & 0x10) LCD_DATA0_PORT |= _BV(LCD_DATA0_PIN);
-        lcd_e_toggle();
-
-        /* output low nibble */
-        LCD_DATA3_PORT &= ~_BV(LCD_DATA3_PIN);
-        LCD_DATA2_PORT &= ~_BV(LCD_DATA2_PIN);
-        LCD_DATA1_PORT &= ~_BV(LCD_DATA1_PIN);
-        LCD_DATA0_PORT &= ~_BV(LCD_DATA0_PIN);
-        if (data & 0x08) LCD_DATA3_PORT |= _BV(LCD_DATA3_PIN);
-        if (data & 0x04) LCD_DATA2_PORT |= _BV(LCD_DATA2_PIN);
-        if (data & 0x02) LCD_DATA1_PORT |= _BV(LCD_DATA1_PIN);
-        if (data & 0x01) LCD_DATA0_PORT |= _BV(LCD_DATA0_PIN);
-        lcd_e_toggle();
-
-        /* all data pins high (inactive) */
-        LCD_DATA0_PORT |= _BV(LCD_DATA0_PIN);