Arduino LCD Message Scroller working

Got my Arduino LCD message scroller working last night, will post a video later when I do an end to end test with my Twitter mentions.

Here is the code (also at GitHub https://github.com/alastairhm/arduino.git)

// Auto scroll a message on the LCD and receive new messages via Serial port.
// Alastair Montgomery (c) 2013
// Version 1.02
 
// include the library code:
#include <LiquidCrystal.h>
#include <string.h>
// initialize the library with the numbers of the interface pins
// below for SainSmart LCD Shield
LiquidCrystal lcd(8, 9, 4, 5, 6, 7);
const int ledWidth = 16;
const int ledDepth = 2;
//Default Message
char msg[256] = “Serial Message Version 1.02”;
char buffer[256];
int newMsg = true;
int previous = 0;
int pos = 0;
void setup() {
  // set up the LCD’s number of columns and rows: 
  lcd.begin(ledWidth,ledDepth);
  Serial.begin(9600);
}
void printLine(int refreshSeconds, int lineNum){
  //Check if the current second since restart is a mod of refresh seconds , 
  //if it is then update the display , it must also not equal the previously 
  //stored value to prevent duplicate refreshes
  if((millis()/1000) % refreshSeconds == 0 && previous != (millis()/1000)){
    previous =  (millis()/1000);  //Store the current time we entered for comparison on the next cycle
    lcd.setCursor(0, lineNum);    //Set our draw position , set second param to 0 to use the top line
    char lcdTop[ledWidth];              //Create a char array to store the text for the line
    int copySize = ledWidth;            // What is the size of our screen , this could probably be moved outside the loop but its more dynamic like this
    if(strlen(msg) < copySize)
    {
        //if the msg is smaller than the current buffer use its length instead;
        copySize = strlen(msg);
    }
    //Store the current position temporarily and invert its sign if its negative since we are going in reverse
    int tempPos = pos;
    if(tempPos < 0)
    {
        tempPos = -(tempPos);
    }
    //Build the lcd text by copying the required text out of our template msg variable 
    memcpy(&lcdTop[0],&msg[tempPos],copySize);
    lcd.print(lcdTop);            //Print it from position 0
    //Increase the current position and check if the position + 16 (screen size) would be larger than the msg length , if it is go in reverse by inverting the sign.
    pos += 1;
    if(pos +copySize >= strlen(msg))
    {
      pos = -(pos);
      lcd.setCursor(0, 0);

      lcd.print("           “);
    }
  }
}
void loop() {
  
  //Read serial
  if (Serial.available()){
    delay(100);
    int i = 0;
    while (Serial.available() > 0 && i<254){
      buffer[i++] = Serial.read();
    }
    buffer[i] = ’\0’;
    strcpy(msg,buffer);
    newMsg = true;
    pos = 0;
  }
 
  if (newMsg){
    lcd.noAutoscroll();
    lcd.clear();
    newMsg = false;
    lcd.setCursor(0, 0);

    lcd.print(“New Message”); 

  }
 
  printLine(1,1);
} 

Still a few rough edges to smooth out but its almost there.

Doodle's Geek Monkey by Alastair Montgomery