LCD displaying black boxes.

[Sunil Hiremath]

Hi friends,

I'm interfacing JHD 162A 16*2 LCD with 89c51 Micro controller. I'm unable to display any character, it always displays half screen black boxes..
Need help....

I have given pin connection details and LCD test code below...

Tried with different MCU and LCD but same thing happening.


D0 - D7 pins of LCD = Port 1
RS = P3.5
R/W = ground
Enable = P3.4

//----------------------------------HEADER Declarations--------------------------------------//
#include <reg51.h>
#include <string.h>
//----------------------------------LCD Declarations--------------------------------------//
void initlcd(void);
void cmd_lcd(unsigned char command);
void data_lcd(unsigned char data2lcd);
void lcd_shortdelay(void);
void delay_ms(unsigned int ms);

#define CLR_LCD cmd_lcd(0x01); delay_ms(5)
#define RETURN_HOME_LCD cmd_lcd(0x02); delay_ms(5)
#define LCD_PORT P1

sbit enable=P3^4;
sbit regsel=P3^5;

void data_mode(void);

void printlcd(unsigned char *message, unsigned char row, unsigned char col);


//----------------------------------MAIN PROGRAM--------------------------------------//

void main(void)
{
initlcd(); //init lcd

while(1)
{

printlcd(" LCD TEST.. ", 0, 0); //print on lcd frist line
cmd_lcd(0x0C); //currsor off
delay_ms(1000);
CLR_LCD;
delay_ms(1000);
RETURN_HOME_LCD;
}
}

//----------------------------------LCD funtions--------------------------------------//

void initlcd()
{
enable=0;
delay_ms(20);
cmd_lcd(0x30);
delay_ms(5);
cmd_lcd(0x30);
cmd_lcd(0x30);
cmd_lcd(0x38);
cmd_lcd(0x08);
CLR_LCD;
cmd_lcd(0x06);
cmd_lcd(0x0e);
}

void cmd_lcd(unsigned char command)
{
LCD_PORT=command;
regsel=0;
enable=1;
enable=0;
lcd_shortdelay();
}

void data_lcd(unsigned char databyte)
{
LCD_PORT=databyte;
regsel=1;
enable=1;
enable=0;
lcd_shortdelay();
}

void printlcd(unsigned char *message, unsigned char row, unsigned char col)
{
cmd_lcd(0x80 + (0x40*row) + col);

for(; *message; message++)
data_lcd(*message);

}

void lcd_shortdelay(void)
{
unsigned char t=23;
while(t--);
}

void delay_ms(unsigned int ms)
{
unsigned char t1;
unsigned int t2;

for(t1=0; t1<ms; t1++){
for(t2=0; t2<711; t2++);
}
}