Problems with scrolling function HELP!

[aries_david]

Does anyone know how to make the texts scroll in an LCD display 16x2 characters....I used the code below and it does display the text but unfortunately i cant make it to scroll...please help...it would greatly apprecited...


[/code]#include <dos.h>
#include <string.h>

#define PORTADDRESS 0x378 /* Enter Your Port Address Here */

#define DATA PORTADDRESS+0
#define STATUS PORTADDRESS+1
#define CONTROL PORTADDRESS+2
#define outportb
#define inportb
#define delay
void main(void)
{
char string[] = {"Testing 1,2,3 "
"It' Works ! "};
char init[10];
int count;
int len;
init[0] = 0x0F; /* Init Display */
init[1] = 0x01; /* Clear Display */
init[2] = 0x38; /* Dual Line / 8 Bits */

outportb(CONTROL, inportb(CONTROL) & 0xDF); /* Reset Control Port - Make sure Forward Direction */

outportb(CONTROL, inportb(CONTROL) | 0x08); /* Set Select Printer (Register Select) */

for (count = 0; count <= 2; count++)
{
outportb(DATA, init[count]);
outportb(CONTROL,inportb(CONTROL) | 0x01); /* Set Strobe (Enable)*/
delay(20); /* Larger Delay for INIT */
outportb(CONTROL,inportb(CONTROL) & 0xFE); /* Reset Strobe (Enable)*/
delay(20); /* Larger Delay for INIT */
}

outportb(CONTROL, inportb(CONTROL) & 0xF7); /* Reset Select Printer (Register Select) */

len = strlen(string);

for (count = 0; count < len; count++)
{
outportb(DATA, string[count]);
outportb(CONTROL,inportb(CONTROL) | 0x01); /* Set Strobe */
delay(2);
outportb(CONTROL,inportb(CONTROL) & 0xFE); /* Reset Strobe */
delay(2);
}
}

[mattcro]

The HD44780-type LCD modules don't have any intelligence built-in to do the scrolling. They can do a limited amount of scrolling functionality by internally shifting all characters left or right, but if you keep shifting, your text appears on another line - it doesn't scroll nicely within one line.

In LCDSmartie and other programs, the scrolling is done by sending the text to the LCD, waiting a short time (depending on scroll speed), then manipulating the text and sending again, manipulating and sending again... and so on.

The string must be shifted in software by 1 character each time, and the character that "drops off the end" must be added to the start of the string. You need to keep track of several things - the width of the display, the number of characters in the string, and the number of characters you've scrolled by...

If you can understand C code, have a look at the source code for the scroll plugin to get an idea how to do the scrolling.

Matt.