My version is the program shown on the right. It simply monitors the state of PORTA bit 0 and prints an appropriate message. It does this so quickly that the message appears to change instantaneously when the button is pressed. I use the & operator to split of the bottom bit of PORTA for the testing.

I hope you didn't forget the set up the ports correctly. The call of lcd_setup will set up those ports needed by the LCD but I have added my own setup function to set up TRISA for PORTA.

Note how I have added spaces onto the end of the "up" message so that the "wn" part of the down message is erased each time the display is updated. Note also I am not clearing the display between redraws. If you do this the screen will flicker horribly.

Run project called Exercise 8.1. Press LA0 and note how the message changes.

/*  Ex 8.1 Reaction Timer        */
/*  Rob Miles April 2000         */

#include <lcdlib.h>

void setup_hardware (void)
{
  /* Set PortA to use digital inputs */
  ANSELA = 0x00;

  /* bits 0-4 of PORTA for input */
  TRISA = 0x1f ;

}

const unsigned char down [5] =
{
  'd','o','w','n',0x00
} ;

const unsigned char up [5] =
{
  'u','p',' ',' ',0x00
} ;

void main ( void )
{

  lcd_start () ;

  setup_hardware () ;

  while (1)
  {
    lcd_cursor ( 0, 0 ) ;

    if ( PORTA & 0x01 )
    {
      lcd_print ( down ) ;
    }
    else
    {
      lcd_print ( up ) ;
    }
  }
}