16x1 LCD only shows 8 leftmost characters

[karan123]

lcd only 8 characters

Hello,

I have written ASM Program for 16 x 1 LCD (with no auxiliary driver) means one IC (or epoxy blob) on Back.

But I have Seen only 8 leftmost characters.

;LCD INTI ROUTINE
mov a,#38h ; 16 x 1 LCD
acall command
mov a,#0eh ; Disply on,Cursor not Blinking
acall command
mov a,#06h ; Increment Cursor
acall command
mov a,#01h ; Clear Disply
acall command
mov a,#80h ; Force Cursor to Begining of First Line
acall command


How I see next 8 Characters?

Thanks in Advance
Karan

 

[GrandAlf]

lcd + 8 character

These are configured electrically as 2x8. Here is driver written in C for 8051, you may be able to pick up some idea from it.

LCD.C
#include <reg51.h>
#include "delay.h"

sbit LCD_RS =P1^0; // Register select
sbit LCD_E =P1^1; // Enable

#define LCD_STROBE ((LCD_E = 1),(LCD_E=0))

// Time in Milliseconds
void DelayMs(unsigned char cnt)
{ cnt=2*cnt;
do
{DelayUs(500);}
while(--cnt != 0);
}

// Send to Display
void lcd_write(unsigned char c)
{
unsigned char Movit;
Movit = (c >> 2);
P1 = (P1 & 0xC3) | (Movit & 0x3C);
LCD_STROBE;
Movit = (c << 2);
P1 = (P1 & 0xC3) | (Movit & 0x3C);
LCD_STROBE;
DelayUs(60);
}

// Clear and home the LCD
void lcd_clear(void)
{
LCD_RS = 0;
lcd_write(0x80);
DelayMs(2);
}

// Position the Cursor
void lcd_goto(unsigned char pos)
{
LCD_RS = 0;
lcd_write (0x80+pos);
}

// Send Character String
void lcd_puts(const char * s)
{
unsigned char cursor = 0x00;

while(*s)
{
LCD_RS = 1;
lcd_write(*s);
s++;
cursor++;
if (cursor==0x08)lcd_goto(0x40); // Change to 0x80 for simulation
if (cursor==0x10){cursor=0;lcd_goto(0x00);}
}
}


// Initialise the LCD - mode 4 bits
void lcd_init(void)
{
LCD_RS = 0;
DelayMs(40); // power on delay
lcd_write(0x28); // 4 bit mode, 1/16 duty, 5x8 font
LCD_STROBE;
DelayMs(5);
LCD_STROBE;
DelayMs(5);
LCD_STROBE;
lcd_write(0x28);
lcd_write(0x08); // display off
lcd_write(0x0C); // display on, cursor off
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)

DELAY.H (if needed)
#define XTAL_FREQ 12
#define DelayUs(x) { unsigned char _dcnt; \
_dcnt = (x)*((XTAL_FREQ)/12); \
while(--_dcnt != 0) \
continue; }

extern void DelayMs(unsigned char);

Added after 6 minutes:

Here is another from CCS site for PICS

// Flex_lcd_16x1.c

// These are randomly assigned pins, used to test
// that the driver can work with any arrangement
// of i/o pins.
#define LCD_DB4 PIN_B4
#define LCD_DB5 PIN_B5
#define LCD_DB6 PIN_B6
#define LCD_DB7 PIN_B7

#define LCD_RS PIN_B0
#define LCD_RW PIN_A2
#define LCD_E PIN_B3



// If you want to use a 6-pin interface for your LCD, then
// connect the R/W pin on the LCD to ground and comment
// out the following line. A 6-pin interface to the LCD
// is used if only have a few free i/o pins available on
// your PIC, and you want to use the smallest possible
// number of pins for the LCD.

//#define USE_LCD_RW 1

//========================================
// Use "2 lines" as the lcd type for the 16x1 LCD.
// The LCD is the same as an 8x2 LCD, but with the
// bottom line appended on the right side of the first line.
#define LCD_TYPE 2 // 0=5x7, 1=5x10, 2=2 lines
#define LCD_2ND_HALF_ADDRESS 0x40

#define LCD_WIDTH 16
#define LCD_HALF_WIDTH (LCD_WIDTH/2)

int8 const LCD_INIT_STRING[4] =
{
0x20 | (LCD_TYPE << 2), // Func set: 4-bit, 2 lines, 5x8 dots
0xc, // Display on
1, // Clear display
6 // Increment cursor
};

int8 lcd_xcoord;


//-------------------------------------
void lcd_send_nibble(int8 nibble)
{
// Note: !! converts an integer expression
// to a boolean (1 or 0).
output_bit(LCD_DB4, !!(nibble & 1));
output_bit(LCD_DB5, !!(nibble & 2));
output_bit(LCD_DB6, !!(nibble & 4));
output_bit(LCD_DB7, !!(nibble & 8));

delay_cycles(1);
output_high(LCD_E);
delay_us(2);
output_low(LCD_E);
}

//-----------------------------------
// This sub-routine is only called by lcd_read_byte().
// It's not a stand-alone routine. For example, the
// R/W signal is set high by lcd_read_byte() before
// this routine is called.

#ifdef USE_LCD_RW
int8 lcd_read_nibble(void)
{
int8 retval;
// Create bit variables so that we can easily set
// individual bits in the retval variable.
#bit retval_0 = retval.0
#bit retval_1 = retval.1
#bit retval_2 = retval.2
#bit retval_3 = retval.3

retval = 0;

output_high(LCD_E);
delay_us(1);

retval_0 = input(LCD_DB4);
retval_1 = input(LCD_DB5);
retval_2 = input(LCD_DB6);
retval_3 = input(LCD_DB7);

output_low(LCD_E);
delay_us(1);

return(retval);
}
#endif

//---------------------------------------
// Read a byte from the LCD and return it.

#ifdef USE_LCD_RW
int8 lcd_read_byte(void)
{
int8 low;
int8 high;

output_high(LCD_RW);
delay_cycles(1);

high = lcd_read_nibble();

low = lcd_read_nibble();

return((high << 4) | low);
}
#endif

//----------------------------------------
// Send a byte to the LCD.
void lcd_send_byte(int8 address, int8 n)
{
output_low(LCD_RS);

#ifdef USE_LCD_RW
while(bit_test(lcd_read_byte(), 7)) ;
#else
delay_us(60);
#endif

if(address)
output_high(LCD_RS);
else
output_low(LCD_RS);

delay_cycles(1);

#ifdef USE_LCD_RW
output_low(LCD_RW);
delay_cycles(1);
#endif

output_low(LCD_E);

lcd_send_nibble(n >> 4);
lcd_send_nibble(n & 0xf);
}

//----------------------------
void lcd_init(void)
{
int8 i;

output_low(LCD_RS);

#ifdef USE_LCD_RW
output_low(LCD_RW);
#endif

output_low(LCD_E);

// Some LCDs require 15 ms minimum delay after
// power-up. Others require 30 ms. I'm going
// to set it to 35 ms, so it should work with
// all of them.
delay_ms(35);

for(i=0 ;i < 3; i++)
{
lcd_send_nibble(0x03);
delay_ms(5);
}

lcd_send_nibble(0x02);

for(i=0; i < sizeof(LCD_INIT_STRING); i++)
{
lcd_send_byte(0, LCD_INIT_STRING);

// If the R/W signal is not used, then
// the busy bit can't be polled. One of
// the init commands takes longer than
// the hard-coded delay of 60 us, so in
// that case, lets just do a 5 ms delay
// after all four of them.
#ifndef USE_LCD_RW
delay_ms(5);
#endif
}

lcd_xcoord = 1;
}

//----------------------------
// The x-coordinate can be 1 to 16.
// The y coordinate is ignored.
// This x,y interface is kept in order to be
// consistent with other CCS LCD drivers.
void lcd_gotoxy(int8 x, int8 y)
{
int8 address;

// Update the global x-coordinate variable with the
// current x coordinate.
lcd_xcoord = x;

// Convert the x-coordinate from CCS format (1-16) to
// the 0-15 format used by the LCD hardware.
address = x - 1;

// If the x-coordinate is within the 2nd half of the
// LCD line, the address must be adjusted because
// of the special architecture of the 8x2 LCD.
if(address >= LCD_HALF_WIDTH)
{
address += (LCD_2ND_HALF_ADDRESS - LCD_HALF_WIDTH);
}

lcd_send_byte(0, 0x80 | address);
}


//-----------------------------
void lcd_putc(char c)
{
switch(c)
{
case '\f':
lcd_send_byte(0,1);
delay_ms(2);
lcd_xcoord = 1;
break;

case '\n':
lcd_gotoxy(1,1); // Goto start of line 1
break;

case '\b':
lcd_send_byte(0, 0x10);
lcd_xcoord--;
if(lcd_xcoord == LCD_HALF_WIDTH)
lcd_gotoxy(LCD_HALF_WIDTH, 1);
break;

default:
lcd_send_byte(1, c);
lcd_xcoord++;
if(lcd_xcoord == (LCD_HALF_WIDTH +1))
lcd_gotoxy(LCD_HALF_WIDTH +1, 1);
break;
}
}

//------------------------------
#ifdef USE_LCD_RW
char lcd_getc(int8 x, int8 y)
{
char value;

lcd_gotoxy(x,y);

// Wait until busy flag is low.
while(bit_test(lcd_read_byte(),7));

output_high(LCD_RS);
value = lcd_read_byte();
output_low(lcd_RS);

return(value);
}
#endif

 

[karan123]

how to initialize single line 16x1 lcd

Thanks for Reply..


But I am using LCD 16 x 1 (with no auxiliary driver on BACK SIDE of LCD)

in 8-BIT MODE.(using all LCD Signals from D0-D7)

Please Suggest me how to INITIALIZE THAT?



KARAN

 

[freedomtruth]

16x1 line lcd display initialization

Hi karan123

There are two different configurations for 16x1 LCDs depending on your manufucturer.
1)the appropriate memory addresses for the 16 characters are 00h - 0Fh. This should be initialized as a 1-line device.
2)first 8 characters are at 00h - 07h and the others are at 40h - 47h. This must be initialized as a 2-line device.

after writing firs 8 characters, move your cursor to the location 40h (9th charachter) using this command: 0C0H

e.g.:

    MOV       A,#0C0H
    ACALL     COMMAND

hope this helps.Let us know the result.