LCD demo
/** LCD interface example
* Uses routines from delay.c
* This code will interface to a standard LCD controller
* like the Hitachi HD44780. It uses it in 4 bit mode, with
* the hardware connected as follows (the standard 14 pin
* LCD connector is used):
*
* PORTB bits 0-3 are connected to the LCD data bits 4-7 (high nibble)
* PORTA bit 2 is connected to the LCD RS input (register select)
* PORTA bit 3 is connected to the LCD EN bit (enable)
*
* To use these routines, set up the port I/O (TRISA, TRISB) then
* call lcd_init(), then other routines as required.
*
*/
#include <pic.h>
#include "lcd.h"
#include "delay.h"
static bit LCD_RS @ ((unsigned)&PORTA*8+2); // Register select
static bit LCD_EN @ ((unsigned)&PORTA*8+3); // Enable
#define LCD_STROBE ((LCD_EN = 1),(LCD_EN=0))
/* write a byte to the LCD in 4 bit mode */
void
lcd_write(unsigned char c)
{
PORTB = (PORTB & 0xF0) |(c >> 4);
LCD_STROBE;
PORTB = (PORTB & 0xF0) |(c & 0x0F);
LCD_STROBE;
DelayUs(40);
}
/*
*Clear and home the LCD
*/
void
lcd_clear(void)
{
LCD_RS = 0;
lcd_write(0x1);
DelayMs(2);
}
/* write a string of chars to the LCD */
void
lcd_puts(const char * s)
{
LCD_RS = 1; // write characters
while(*s)
lcd_write(*s++);
}
/* write one character to the LCD */
void
lcd_putch(char c)
{
LCD_RS = 1; // write characters
PORTB = (PORTB & 0xF0) |(c >> 4);
LCD_STROBE;
PORTB = (PORTB & 0xF0) |(c & 0x0F);
LCD_STROBE;
DelayUs(40);
}
/*
* Go to the specified position
*/
void
lcd_goto(unsigned char pos)
{
LCD_RS = 0;
lcd_write(0x80+pos);
}
/* initialise the LCD - put into 4 bit mode */
void
lcd_init(void)
{
LCD_RS = 0; // write control bytes
DelayMs(15); // power on delay
PORTB = 0x3; // attention!
LCD_STROBE;
DelayMs(5);
LCD_STROBE;
DelayUs(100);
LCD_STROBE;
DelayMs(5);
PORTB = 0x2; // set 4 bit mode
LCD_STROBE;
DelayUs(40);
lcd_write(0x28); // 4 bit mode, 1/16 duty, 5x8 font
lcd_write(0x08); // display off
lcd_write(0x0F); // display on, blink curson on
lcd_write(0x06); // entry mode
}
=================================================================================
LCD.h
/*
* LCD interface header file
* See lcd.c for more info
*/
/* write a byte to the LCD in 4 bit mode */
extern void lcd_write(unsigned char);
/* Clear and home the LCD */
extern void lcd_clear(void);
/* write a string of characters to the LCD */
extern void lcd_puts(const char * s);
/* Go to the specified position */
extern void lcd_goto(unsigned char pos);
/* intialize the LCD - call before anything else */
extern void lcd_init(void);
extern void lcd_putch(char);
/* Set the cursor position */
#define lcd_cursor(x) lcd_write(((x)&0x7F)|0x80)
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