Scroll function

Tumbler

Hello

I'm trying to make a scroll function for the 4x20 lcd

public static void main() {
    Uart txOut = new Uart(Uart.dirTransmit, LCD_PIN, Uart.dontInvert,
                          Uart.speed19200,Uart.stop1);
    Serial_LCD4x20 myLCD = new  Serial_LCD4x20(txOut);
    myLCD.clearDisplay();
    String [noparse][[/noparse]] display;
    display = new String[noparse][[/noparse]5];
    display[noparse][[/noparse]0] ="1                   "; //lcd module line 1
    display[noparse][[/noparse]1] ="2                   "; //lcd module line 2
    display[noparse][[/noparse]2] ="3                   "; //lcd module line 3
    display[noparse][[/noparse]3] ="4                   "; //lcd module line 4
    display[noparse][[/noparse]4] ="                    "; //
    
    StringBuffer buf= new StringBuffer(255);
    boolean scroll=false;
    while(true){                                  // endless loop
      while(rxUart.byteAvailable()){              // look if received data
              char c=(char)rxUart.receiveByte();  // get the data
              buf.append(c);                      // and put into buffer
              scroll=true;
      }
      display[noparse][[/noparse]4]=buf.toString();                  //copy buf to display line 4
      buf.clear();                                // empty the buffer
      if(scroll){
        //scroll display array
        for(int i=0;i<4;i++){
              System.out.println("Copy display line ("+(i+1)+") to display line ("+i+"):"+ display[noparse][[/noparse]i+1]+"->"+display[noparse][[/noparse]i]);
           display[noparse][[/noparse]i]=display[noparse][[/noparse]i+1];               // copy display line i+1 to display line i
        }//end for
        
        // copy display array into lcd
        for(int i=0;i<4;i++){
           myLCD.setPosition(i,0);
           myLCD.write(display[noparse][[/noparse]i]);
        }// end for
        scroll=false;
      }//end if(scroll)
    }//end while
  }//end main

When i send a string it will be copied to display[noparse][[/noparse]4]
during a scroll every line scrolls up, and the display[noparse][[/noparse]4] line shows in the LCD
but when i send another string, the screen scrolls up like it has to do, but the last 2 lines have the same text. (last send string)

And i'm not know what i'm doing wrong here

example

first time i start the program
output to lcd
1
2
3
4

now i send "PARALLAX"
displays shows
2
3
4
PARALLAX

send another string: "JAVELIN"
display shows now:
3
4
JAVELIN
JAVELIN




Post Edited (Tumbler) : 6/14/2009 10:40:05 AM GMT

Peter Verkaik

What happens is that you shift up the string pointers,
rather than the string contents.
You need to rotate the string pointers (better use string buffers)

[size=2][code]
public static void main() {
    Uart txOut = new Uart(Uart.dirTransmit, LCD_PIN, Uart.dontInvert,
                          Uart.speed19200,Uart.stop1);
    Serial_LCD4x20 myLCD = new  Serial_LCD4x20(txOut);
    myLCD.clearDisplay();
    StringBuffer[noparse][[/noparse]] display = new StringBuffer[noparse][[/noparse]5];
    StringBuffer Temp;
    for (int i=0; i<5; i++) {
      display[noparse][[/noparse]i] = new StringBuffer();
    }

    display[noparse][[/noparse]0].Append("1                   "); //lcd module line 1
    display[noparse][[/noparse]1].Append("2                   "); //lcd module line 2
    display[noparse][[/noparse]2].Append("3                   "); //lcd module line 3
    display[noparse][[/noparse]3].Append("4                   "); //lcd module line 4

    
    boolean scroll=false;
    while(true){                                  // endless loop
      while(rxUart.byteAvailable()){              // look if received data
              char c=(char)rxUart.receiveByte();  // get the data
              display[noparse][[/noparse]4].append(c);                      // and put into buffer
              scroll=true;
      }
      if(scroll){
        //scroll display array (rotate buffer pointers)
        Temp = display[noparse][[/noparse]0];
        display[noparse][[/noparse]0] = display[noparse][[/noparse]1];
        display[noparse][[/noparse]1] = display[noparse][[/noparse]2];
        display[noparse][[/noparse]2] = display[noparse][[/noparse]3];
        display[noparse][[/noparse]3] = display[noparse][[/noparse]4];

        display[noparse][[/noparse]4] = Temp;
        display[noparse][[/noparse]4].Clear(); //will be filled with received bytes
        
        // copy display array into lcd
        for(int i=0;i<4;i++){
           myLCD.setPosition(i,0);
           myLCD.write(display[noparse][[/noparse]i]);
        }// end for
        scroll=false;
      }//end if(scroll)
    }//end while
  }//end main

[/code][/size]

regards peter

Tumbler

Ok, thx Peter. Working now
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