/*
   This program reads strings from the serial console, and displays them on the LCD.

   The message received will be scrolled unless/until the button is pressed to clear the display.

   At that point only the display of a new messages will reset
   the output.

*/

// include the library code:
#include <LiquidCrystal.h>

// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

// The clear-button
#define CLEAR 7

// The two lines of text.
char one[128];
char two[128];

// The input-buffer for text from the serial-console
char input[128];
byte index = 0;

// The scroll-offset for the first line of text.
int offset = 0;

void setup() {
  // set up the number of columns and rows on the LCD
  lcd.begin(16, 2);

  // The button we read for clearing the display.
  pinMode(CLEAR, INPUT);

  Serial.begin(9600);
  Serial.write("Power On");

  strcpy( one, "This is the default message." );
  strcpy( two, "by Steve" );

}

void loop() {

  // If we're clearing
  if ( digitalRead(CLEAR) == LOW ) {
    // Turn off the display
    lcd.noDisplay();

    // empty our display-buffer
    memset( one, '\0', sizeof(one));
    return;
  }


  // If we have serial input available ..
  while (Serial.available() > 0)
  {
    // And we've not yet filled our input buffer.
    if (index < sizeof(input))
    {
      // Read & store the next character
      input[index] = Serial.read();
      index++;
      input[index] = '\0';
    }
  }

  //
  // If we have a string with "#" as the last character we can update our message
  //
  if ( strstr( input, "#" ) > 0 )
  {
    Serial.print( "Read from serial : '");
    Serial.print( input );
    Serial.print( "'\n" );

    // Copy this text to the first-line.
    strcpy( one, input);

    // Replace the "#" with a null-terminator
    one[strlen(one) - 1] = '\0';

    // Replace any non-printable characters with a space.
    for( int i = 0 ; i < strlen( one ); i++ )
       if ( !isprint( one[i] ) )
           one[i] = ' ';

    // Add spaces to the end, so it scrolls off the display neatly.
    for ( int i = 0; i < 16; i++ )
      strcat( one, " " );

    //
    // Empty our input buffer, and reset our stcroll-state.
    //
    memset( input, '\0', sizeof(input) );
    index = 0;
    offset = 0;
  }

  // If our text is empty - then do nothing
  if ( strlen(one) < 1 )
    return;

  // Otherwise restore the display
  lcd.display();

  // Move to the top-left.
  lcd.setCursor(0, 0);

  // Draw 16 characters from the start of the first string.
  for ( int i = 0; i < 16; i++ )
  {
    int c = i + offset;
    if ( c < strlen( one ) )
      lcd.write(one[c]);
  }

  // Show the second inline.
  lcd.setCursor(0, 1);
  lcd.print( two );

  // Handle scrolling the first line
  offset += 1;
  if ( (offset + 16) > strlen(one) )
    offset = 0;

  delay(500);
}