lcd.c

本程式通过4*4键盘的输入控制步进马达的正转和反转,停止转动以及加速和减速.

 /*	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 4 is connected to the LCD RS input (register select)
 *	PORTB 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.
 *	
 */
#ifndef XTAL FREQ
#define	XTAL_FREQ	4MHZ		/* Crystal frequency in MHz */
#endif

#include	<pic.h>
#include	"lcd.h"
#include	"delay.h"

 
#define	PORTBIT(adr, bit)	((unsigned)(&adr)*8+(bit)) 
 
static bit LCD_RS	@ PORTBIT(PORTA, 4);	// Register select
static bit LCD_EN	@ PORTBIT(PORTB, 3);	// Enable
static bit	spkr  @	PORTBIT(PORTA, 0);


void
lcd_strobe(void)
{
	LCD_EN = 1	;
	DelayUs(1);
	LCD_EN = 0	;
	DelayUs(1);
}

void
lcd_write(unsigned char c)
{
	PORTB = (PORTB & 0x0F) |  (c & 0xF0);		/*es. A=65 =>0100 0001 bin  >>4 avremo 0000 0100 or PORTB&11110000 */
	lcd_strobe();
	PORTB = (PORTB & 0x0F) |  (c << 4);	/* 0100 0001 & 00001111 = 0000 0001 */ 
	lcd_strobe();
	DelayUs(50);
}

/*
 * 	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 & 0x0F) |  (c & 0xF0);
	lcd_strobe();
	PORTB = (PORTB & 0x0F) |  (c << 4);
	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 'comando'
	DelayMs(50);	// power on delay
	PORTB = 0x30;	// attention!
	lcd_strobe();
	DelayMs(5);
	lcd_strobe();
	DelayUs(100);
	lcd_strobe();
	DelayMs(1);
	PORTB = 0x20;	// set 4 bit mode
	lcd_strobe();
	DelayMs(1);
	lcd_write(0x28);	// 4 bit mode, 1/16 duty, 5x8 font
	lcd_write(0x06);	// entry mode
	lcd_write(0x0C);	// display on
	lcd_clear();	// clear

}