Trục trặc với LCD

[hangocminh1989]

em có con lcd 1602A mà sao vật vã mấy ngày nay không thể nào cho nó hiển thị nổi 1 kí tự các bác ơi.
các bác xem giúp em có vấn đề gì không nhé.
dưới đây là code và sơ đồ kết nối
#include <16f877a.h>
#include <DEF_877A.H>
#fuses HS,NOWDT,NOPROTECT,NOLVP
#use delay(clock=20000000)
#use fast_io(a)
#use fast_io(b)
#use fast_io(c)
#use fast_io(d)
#use fast_io(e)
struct lcd_pin_map { // This structure is overlayed
BOOLEAN rs; // on to an I/O port to gain
BOOLEAN rw; // access to the LCD pins.
BOOLEAN enable; // The bits are allocated from
BOOLEAN unused; // low order up. ENABLE will
int data : 4; // be pin B0.
} lcd;
#if defined use_portb_lcd
//#locate lcd = getenv("sfr:PORTB") // This puts the entire structure over the port
#ifdef __pch__
#locate lcd = 0xf81
#else
#locate lcd = 6
#endif
#define set_tris_lcd(x) set_tris_b(x)
#else
//#locate lcd = getenv("sfr:PORTD") // This puts the entire structure over the port
#ifdef __pch__
#locate lcd = 0xf83
#else
#locate lcd = 8
#endif
#define set_tris_lcd(x) set_tris_d(x)
#endif
#ifndef lcd_type
#define lcd_type 2 // 0=5x7, 1=5x10, 2=2 lines
#define lcd_line_two 0x40 // LCD RAM address for the second line
#define set_tris_lcd(x) set_tris_d(x)
BYTE const LCD_INIT_STRING[4] = {0x20 | (lcd_type << 2), 0xc, 1, 6};
// These bytes need to be sent to the LCD
// to start it up.
// The following are used for setting
// the I/O port direction register.
struct lcd_pin_map const LCD_WRITE = {0,0,0,0,0}; // For write mode all pins are out
struct lcd_pin_map const LCD_READ = {135,0,0,0,0,}; // For read mode data pins are in
BYTE lcd_read_byte() {
BYTE low,high;
set_tris_lcd(LCD_READ);
lcd.rw = 1;
delay_cycles(1);
lcd.enable = 1;
delay_cycles(1);
high = lcd.data;
lcd.enable = 0;
delay_cycles(1);
lcd.enable = 1;
delay_us(1);
low = lcd.data;
lcd.enable = 0;
set_tris_lcd(LCD_WRITE);
return( (high<<4) | low);
}
void lcd_send_nibble( BYTE n ) {
lcd.data = n;
delay_cycles(1);
lcd.enable = 1;
delay_us(2);
lcd.enable = 0;
}
void lcd_send_byte( BYTE address, BYTE n ) {

lcd.rs = 0;
while ( bit_test(lcd_read_byte(),7) ) ;
lcd.rs = address;
delay_cycles(1);
lcd.rw = 0;
delay_cycles(1);
lcd.enable = 0;
lcd_send_nibble(n >> 4);
lcd_send_nibble(n & 0xf);
}
void lcd_init()
{
BYTE i;
set_tris_lcd(LCD_WRITE);
lcd.rs = 0;
lcd.rw = 0;
lcd.enable = 0;
delay_ms(15);
for(i=1;i<=3;++i) {
lcd_send_nibble(3);
delay_ms(5);
}
lcd_send_nibble(2);
for(i=0;i<=3;++i)
lcd_send_byte(0,LCD_INIT_STRING[i]);
}
void lcd_gotoxy( BYTE x, BYTE y) {
BYTE address;

if(y!=1)
address=lcd_line_two;
else
address=0;
address+=x-1;
lcd_send_byte(0,0x80|address);
}
void lcd_putc( char c) {
switch (c) {
case '\f' : lcd_send_byte(0,1);
delay_ms(2);
break;
case '\n' : lcd_gotoxy(1,2); break;
case '\b' : lcd_send_byte(0,0x10); break;
default : lcd_send_byte(1,c); break;
}
}
char lcd_getc( BYTE x, BYTE y) {
char value;

lcd_gotoxy(x,y);
while ( bit_test(lcd_read_byte(),7) ); // wait until busy flag is low
lcd.rs=1;
value = lcd_read_byte();
lcd.rs=0;
return(value);
}
void main()
{
lcd_init();
set_tris_d(0x00);
//set_tris_c(0x00);
while(1);
{
//output_high(pin_c0);
//delay_ms(200);
//output_low(pin_c2);
//delay_ms(200);
//setup_timer_2(T2_DIV_BY_4,124,1);
//SETUP_CCP2(CCP_PWM);
//SET_PWM2_DUTY(50);
lcd_putc("hello pic");
}
}
thanks