[nampham]

các cao thủ giúp em với, em thử giao tiếp chế độ 4 bit theo cách anh Bắc bảo nưng trên con 16f877a, nhưng mãi ko chạy. các cao thủ xin giúp em với:

#include<pic.h>
__CONFIG(HS & PWRTEN & BOREN & LVPDIS & WDTDIS );

/*======================================================================================
Define LCD_PORT
======================================================================================*/
#define		LCD_DATA_PORT		PORTB					// Port on which LCD data lines are connected
#define		LCD_TRIS_PORT		TRISB					// Need to specify the corresponding TRIS

#define 	LCD_RS				RB1
#define 	LCD_RW				RB2
#define 	LCD_E				RB0

#define		LCD_TRIS_RS			TRISB1
#define 	LCD_TRIS_RW			TRISB2
#define 	LCD_TRIS_E			TRISB0

#define		LCD_TRIS_DATAMASK	(0b11110000)			// Define the bitmask used to read/write the data bits
#define		LCD_D4_BIT			4			

#define LCD_FUNCTION_SET  		((unsigned char)(0b00101000))
#define LCD_DISPLAY_CONTROL 	((unsigned char)(0b00001100))
#define LCD_ENTRY_MODE	 		((unsigned char)(0b00000110))
#define	LCD_COMMAND_CLEAR		((unsigned char)(0x01))	//1.53 ms	// Clear screen, home cursor, unshift display
#define	LCD_COMMAND_HOME		((unsigned char)(0x02))	//1.53 ms	// Home cursor, unshift display
 
// ==================== Declare some functions
void	delay_us (unsigned char us);
void 	delay_ms(unsigned char  ms);
unsigned char LCD_getByte (void);
void 	LCD_PrByte (unsigned char  c);
//void	LCD_Command(unsigned char c);
void 	LCD_PrChar (unsigned char  c);
//void	LCD_gotoXY(unsigned char row, unsigned char col);
//unsigned char  LCD_getChar (void);						// Read character at cursor
void 	LCD_Init(void);
void 	LCD_PrString (const char *message); 
void 	lcd_putnybble (unsigned char  c);

/*=====================================================================================
  Main function
=====================================================================================*/
void main()
{
    TRISB = 0x00;
	PORTB = 0xFF;

	LCD_Init();
	LCD_PrString("I Love You");
	while(1);
}
//==========================================================================================
void delay_us (unsigned char us){
	while(us--){
		asm("nop");
		asm("nop");
	};
}

//==========================================================================================
void delay_ms(unsigned char  ms){
	unsigned char	i, j;
	while(ms--){
		for (i = 0; i < 20; i++)
			for (j = 0; j < 100; j++)
				asm("nop");
		};
}
//==========================================================================================
void LCD_Init(void)
{
	
	 LCD_TRIS_PORT &= ~LCD_TRIS_DATAMASK;				// Set data bus to output 

	 LCD_TRIS_E 		= 	0;
	 LCD_TRIS_RW 	    =	0;
	 LCD_TRIS_RS 		=	0;

	 LCD_E = 0 ;
	 LCD_RS = 0;
	 LCD_RW = 0;
	 delay_ms (15);							  //   Tao tre 15ms cho LCD khoi dong

	lcd_putnybble(0b0010);				    	// Set LCD into 4-bit mode
	delay_ms(10);
	lcd_putnybble(0b0010);
	//delay_ms(10);	
	
	LCD_PrByte (LCD_FUNCTION_SET); 		//Function set  ; DL = 0(4 bits) , N = 1 (2 lines), F = 0 (5x8 dots)
    LCD_PrByte (LCD_DISPLAY_CONTROL);		// Display on/off control 
	LCD_PrByte (LCD_ENTRY_MODE);		// Entry mode set

	LCD_PrByte(LCD_COMMAND_CLEAR);
	delay_ms (2);
	LCD_PrByte(LCD_COMMAND_HOME);
	delay_ms (2);
}
//====================================================================================================
void LCD_PrByte (unsigned char  c)
{						
	unsigned char RS_Status;			// Write byte to port in current RS mode
	RS_Status = LCD_RS;					// Get old pin state
	LCD_RS = 0;							// Force into command mode to read state
	while (LCD_getByte () & 0x80);		// Wait for read state
	if (RS_Status)
		LCD_RS = 1;						// Restore RS to old state		
	delay_us (1);
	LCD_RW = 0;							// Set to write mode
	delay_us (1);
	
	lcd_putnybble (c >> 4);				// Send the character out
	lcd_putnybble (c);
}
//================================================================================================
unsigned char LCD_getByte (void)
{
	unsigned char retval; 									// Return value
	unsigned char highbits ;
	LCD_TRIS_PORT = LCD_TRIS_DATAMASK;		 	// Set port to read mode for data pins
	LCD_RW = 1;											// Tell LCD we want to read
	delay_ms (1);
	LCD_E = 1;
	highbits = (((LCD_DATA_PORT & LCD_TRIS_DATAMASK) >> LCD_D4_BIT) << 4);// Grab high bits and shift to right place
	LCD_E = 0;
	delay_ms (1);
	LCD_E = 1;
	delay_ms (1);
	retval = ((LCD_DATA_PORT & LCD_TRIS_DATAMASK) >> LCD_D4_BIT);	// Grab low bits
	LCD_E = 0;
	retval |= highbits;
	LCD_TRIS_PORT =0x00;//&= ~LCD_TRIS_DATAMASK;				// Set port back to output mode
	return (retval);
}
//====================================================================================================
void lcd_putnybble (unsigned char  c)						// Write nybble to port in current RS mode
	{
	c = c << LCD_D4_BIT;					              	// Shift over to correct bit column
	c &= LCD_TRIS_DATAMASK;						// Remove any extraneous bits
	LCD_DATA_PORT = (LCD_DATA_PORT & ~LCD_TRIS_DATAMASK) | c;	// Write data bits to port
	delay_us (1);
	LCD_E = 1;							// Start to write it
	delay_us (1);
	LCD_E = 0;							// Finish write cycle
	}
//============================================================================
void LCD_PrString (const char *message){					// Write message to LCD (C string type)

	while (*message)						//	Look for end of string
		LCD_PrChar (*message++);					//	Show and bump
}
//============================================================================
/*Ham yeu cau goi du lieu hien thi len LCD*/
void LCD_PrChar (unsigned char  c){						// Write character to LCD
	LCD_RS = 1 ;
	LCD_PrByte(c);
}
//============================================================================