Thread: Trying to scroll a message across an LED display

Hi!

I am trying to scroll a block of text across a segmented LED screen but I am unable to have the entire message scroll across.

I have been able to scroll the letters one at a time and upon reaching the end, the next letter begins. I've also been able to scroll the message across but the letters constantly change as they scroll.

I am trying to achieve this type of scroll:

- - - - - - - c
- - - - - - c o
- - - - - c o d
- - - - c o d e
- - - c o d e -
- - c o d e - -
- c o d e - - -
c o d e - - - -
o d e - - - - -
d e - - - - - -
e - - - - - - -
- - - - - - - -
repeat...

However, I cannot figure out the way to work my increments/decrements in my function.


this is the code i wrote to control the scrolling/increments/decrements but I can't figure out how to write it so to achieve the goal.

Code:

void write_chars(int digit)
{
     int position;
     int space = 8;
   
     position = NUM_DISPLAYS - 1;
     
     do{
   
           write_letter(digit, position);
           position--;
           digit++;
           write_space(space--);

           
           Sleep(DELAY_TIME);
           
       }while(position > -2 );
}


void write_letter(int ch, int position)
{
     static char chars_table[] = {131, 163, 179, 143};
     
     write_display(chars_table[ch], position);
}


void write_space(int position)
{
     int pos;
     
     for ( pos = position; pos < NUM_DISPLAYS; pos++ )
     {
         write_display(SPACE_CH, pos);
     }         
}

Could someone be kind enough to help/guide me to the solution to this problem? (probably seems too easy but I just can't figure it out. Frustrating.)

thanks..