299 lines
7.7 KiB
Markdown
299 lines
7.7 KiB
Markdown
# HD44780 LCD Driver
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## Supported Hardware
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LCD modules using [HD44780U](https://www.sparkfun.com/datasheets/LCD/HD44780.pdf) IC or equivalent, communicating in 4-bit mode.
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|Module|Size |Notes |
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|------|--------------|---------------------------------|
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|1602A |16x2, 5x8 dots| |
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|2004A |20x4, 5x8 dots|Untested, not currently supported|
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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.
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## Usage
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Add the following to your `rules.mk`:
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```make
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HD44780_ENABLE = yes
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```
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## Basic Configuration
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Add the following to your `config.h`:
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|Define |Default |Description |
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|-----------------------|--------------|-----------------------------------------------------------------------------------------------------|
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|`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 }`|
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|`HD44780_RS_PIN` |*Not defined* |(Required) The GPIO connected to the display's RS pin |
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|`HD44780_RW_PIN` |*Not defined* |(Required) The GPIO connected to the display's RW pin |
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|`HD44780_E_PIN` |*Not defined* |(Required) The GPIO connected to the display's E pin |
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|`HD44780_DISPLAY_COLS` |`16` |The number of visible characters on a single line of the display |
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|`HD44780_DISPLAY_LINES`|`2` |The number of visible lines on the display |
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|`HD44780_WRAP_LINES` |*Not defined* |If defined, input characters will wrap to the next line |
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## Examples
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### Hello World
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Add the following to your `keymap.c`:
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```c
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void keyboard_post_init_user(void) {
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hd44780_init(true, true); // Show blinking cursor
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hd44780_puts_P(PSTR("Hello, world!\n"));
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}
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```
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### Custom Character Definition
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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.
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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.
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```
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Byte | 16 8 4 2 1
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1 | x x x ■ □ ■ □ ■
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2 | x x x ■ □ ■ □ ■
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3 | x x x ■ □ ■ □ ■
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4 | x x x □ ■ ■ ■ □
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5 | x x x □ □ ■ □ □
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6 | x x x □ □ ■ □ □
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7 | x x x □ □ ■ □ □
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8 | x x x □ □ □ □ □
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```
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```c
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const uint8_t PROGMEM psi[8] = { 0x15, 0x15, 0x15, 0x0E, 0x04, 0x04, 0x04, 0x00 };
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void keyboard_post_init_user(void) {
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hd44780_init(false, false);
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hd44780_define_char_P(0, psi);
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// Cursor is incremented while defining characters so must be reset
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hd44780_home();
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// 0x08 to avoid null terminator
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hd44780_puts_P(PSTR("\x08 QMK Firmware"));
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}
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```
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## API
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### `void hd44780_init(bool cursor, bool blink)`
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Initialize the display.
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This function should be called only once, before any of the other functions can be called.
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#### Arguments
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- `bool cursor`
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Whether to show the cursor.
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- `bool blink`
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Whether to blink the cursor, if shown.
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---
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### `void hd44780_clear(void)`
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Clear the display.
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This function is called on init.
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---
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### `void hd44780_home(void)`
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Move the cursor to the home position.
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This function is called on init.
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---
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### `void hd44780_on(bool cursor, bool blink)`
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Turn the display on, and/or set the cursor properties.
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This function is called on init.
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#### Arguments
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- `bool cursor`
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Whether to show the cursor.
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- `bool blink`
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Whether to blink the cursor, if shown.
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---
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### `void hd44780_off(void)`
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Turn the display off.
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---
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### `void hd44780_set_cursor(uint8_t col, uint8_t line)`
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Move the cursor to the specified position on the display.
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#### Arguments
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- `uint8_t col`
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The column number to move to, from 0 to 15 on 16x2 displays.
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- `bool line`
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The line number to move to, either 0 or 1 on 16x2 displays.
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---
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### `void hd44780_putc(char c)`
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Print a character to the display. The newline character `\n` will move the cursor to the start of the next line.
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The exact character shown may depend on the ROM code of your particular display - refer to the datasheet for the full character set.
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#### Arguments
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- `char c`
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The character to print.
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---
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### `void hd44780_puts(const char *s)`
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Print a string of characters to the display.
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#### Arguments
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- `const char *s`
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The string to print.
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### `void hd44780_puts_P(const char *s)`
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Print a string of characters from PROGMEM to the display.
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On ARM devices, this function is simply an alias of `hd44780_puts()`.
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#### Arguments
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- `const char *s`
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The PROGMEM string to print (ie. `PSTR("Hello")`).
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---
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### `void hd44780_define_char(uint8_t index, uint8_t *data)`
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Define a custom character.
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#### Arguments
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- `uint8_t index`
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The index of the custom character to define, from 0 to 7.
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- `uint8_t *data`
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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.
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### `void hd44780_define_char_P(uint8_t index, const uint8_t *data)`
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Define a custom character from PROGMEM.
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On ARM devices, this function is simply an alias of `hd44780_define_char()`.
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#### Arguments
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- `uint8_t index`
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The index of the custom character to define, from 0 to 7.
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- `const uint8_t *data`
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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.
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---
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### `bool hd44780_busy(void)`
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Indicates whether the display is currently processing, and cannot accept instructions.
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#### Return Value
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`true` if the display is busy.
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### `void hd44780_write(uint8_t data, bool isData)`
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Write a byte to the display.
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#### Arguments
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- `uint8_t data`
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The byte to send to the display.
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- `bool isData`
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Whether the byte is an instruction or character data.
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---
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### `uint8_t hd44780_read(bool isData)`
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Read a byte from the display.
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#### Arguments
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- `bool isData`
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Whether to read the current cursor position, or the character at the cursor.
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#### Return Value
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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.
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---
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### `void hd44780_command(uint8_t command)`
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Send a command to the display. Refer to the datasheet and `hd44780.h` for the valid commands and defines.
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This function waits for the display to clear the busy flag before sending the command.
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#### Arguments
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- `uint8_t command`
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The command to send.
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---
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### `void hd44780_data(uint8_t data)`
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Send a byte of data to the display.
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This function waits for the display to clear the busy flag before sending the data.
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#### Arguments
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- `uint8_t data`
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The byte of data to send.
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---
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### `void hd44780_set_cgram_address(uint8_t address)`
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Set the CGRAM address.
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This function is used when defining custom characters.
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#### Arguments
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- `uint8_t address`
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The CGRAM address to move to, from `0x00` to `0x3F`.
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---
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### `void hd44780_set_ddram_address(uint8_t address)`
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Set the DDRAM address.
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This function is used when printing characters to the display, and setting the cursor.
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#### Arguments
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- `uint8_t address`
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The DDRAM address to move to, from `0x00` to `0x7F`.
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