The LCD understands a number of commands which are designed to be used on a range of different configurations of panel. We do not have the time or the space to go into these in any detail right now, although a data sheet for the commands is available for reference. Instead I will just give the commands which we need to use to set the panel up and make it ready for action.

I constructed the commands by creating the bit patterns from the data sheet and then converting them into hex for inclusion in the program.

The function setup_lcd sends all five bytes of the lcd_init array and then calls the clear function to clear the display and make it ready for use.

Note also that I set up the hardware in this function, being careful not to change the settings on bits of PORTB which I am not using. I also perform a short delay to let the LCD settle if we are being called just after the power going on.

Load and run Exercise 5.1 and see how it displays a message on the LCD panel.

const unsigned char lcd_init [5] =
{
/*  LCD initialize                */
    0x33,
/*  Set for 4 bit operation       */
    0x32,
/*  Set for 2 line LCD            */
    0x2c,
/*  Select move after write       */
    0x06,
/*  disp. on cursor off blink off */
    0x0c
} ;

char lcd_start (void)
{
  unsigned char i ;

  /* set bits of PORTB for output  */
  /* change for different hardware */
  /* clear bottom five bits for LCD*/
  /* don't change any other bits   */
  TRISB = (trtisb & 0xc0) ;

  /* give the LCD time to settle */
  /* from power up               */
  lcd_delay ( POWER_UP_DELAY ) ;

  for ( i=0 ; i < 5 ; i++ )
  {
    lcd_command ( lcd_init [i] ) ;
  }

  lcd_clear () ;

  /*  say we worked              */
  return 1 ;
}