8.9 KiB
HD44780 LCD Driver :id=hd44780-lcd-driver
Supported Hardware :id=supported-hardware
LCD modules using HD44780U 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 for more details.
Usage :id=usage
Add the following to your rules.mk:
HD44780_ENABLE = yes
Basic Configuration :id=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 :id=examples
Hello World :id=example-hello-world
Add the following to your keymap.c:
void keyboard_post_init_user(void) {
hd44780_init(true, true); // Show blinking cursor
hd44780_puts_P(PSTR("Hello, world!\n"));
}
Custom Character Definition :id=example-custom-character
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 □ □ □ □ □
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 :id=api
void hd44780_init(bool cursor, bool blink) :id=api-hd44780-init
Initialize the display.
This function should be called only once, before any of the other functions can be called.
Arguments :id=api-hd44780-init-arguments
bool cursor
Whether to show the cursor.bool blink
Whether to blink the cursor, if shown.
void hd44780_clear(void) :id=api-hd44780-clear
Clear the display.
This function is called on init.
void hd44780_home(void) :id=api-hd44780-home
Move the cursor to the home position.
This function is called on init.
void hd44780_on(bool cursor, bool blink) :id=api-hd44780-on
Turn the display on, and/or set the cursor properties.
This function is called on init.
Arguments :id=api-hd44780-on-arguments
bool cursor
Whether to show the cursor.bool blink
Whether to blink the cursor, if shown.
void hd44780_off(void) :id=api-hd44780-off
Turn the display off.
void hd44780_set_cursor(uint8_t col, uint8_t line) :id=api-hd44780-set-cursor
Move the cursor to the specified position on the display.
Arguments :id=api-hd44780-set-cursor-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) :id=api-hd44780-putc
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 :id=api-hd44780-putc-arguments
char c
The character to print.
void hd44780_puts(const char *s) :id=api-hd44780-puts
Print a string of characters to the display.
Arguments :id=api-hd44780-puts-arguments
const char *s
The string to print.
void hd44780_puts_P(const char *s) :id=api-hd44780-puts-p
Print a string of characters from PROGMEM to the display.
On ARM devices, this function is simply an alias of hd44780_puts().
Arguments :id=api-hd44780-puts-p-arguments
const char *s
The PROGMEM string to print (ie.PSTR("Hello")).
void hd44780_define_char(uint8_t index, uint8_t *data) :id=api-hd44780-define-char
Define a custom character.
Arguments :id=api-hd44780-define-char-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) :id=api-hd44780-define-char-p
Define a custom character from PROGMEM.
On ARM devices, this function is simply an alias of hd44780_define_char().
Arguments :id=api-hd44780-define-char-p-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) :id=api-hd44780-busy
Indicates whether the display is currently processing, and cannot accept instructions.
Return Value :id=api-hd44780-busy-arguments
true if the display is busy.
void hd44780_write(uint8_t data, bool isData) :id=api-hd44780-write
Write a byte to the display.
Arguments :id=api-hd44780-write-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) :id=api-hd44780-read
Read a byte from the display.
Arguments :id=api-hd44780-read-arguments
bool isData
Whether to read the current cursor position, or the character at the cursor.
Return Value :id=api-hd44780-read-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.
void hd44780_command(uint8_t command) :id=api-hd44780-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 :id=api-hd44780-command-arguments
uint8_t command
The command to send.
void hd44780_data(uint8_t data) :id=api-hd44780-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 :id=api-hd44780-data-arguments
uint8_t data
The byte of data to send.
void hd44780_set_cgram_address(uint8_t address) :id=api-hd44780-set-cgram-address
Set the CGRAM address.
This function is used when defining custom characters.
Arguments :id=api-hd44780-set-cgram-address-arguments
uint8_t address
The CGRAM address to move to, from0x00to0x3F.
void hd44780_set_ddram_address(uint8_t address) :id=api-hd44780-set-ddram-address
Set the DDRAM address.
This function is used when printing characters to the display, and setting the cursor.
Arguments :id=api-hd44780-set-ddram-address-arguments
uint8_t address
The DDRAM address to move to, from0x00to0x7F.