qmk-firmware/docs/feature_hd44780.md

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.

You can enable support for HD44780 Displays by setting the HD44780_ENABLE flag in your keyboards rules.mk to yes. This will use about 400 KB of extra space.

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

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_clrsrc().

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").

There are more methods available to control the display. For in depth documentation please visit the linked page.