Hi all. I'm trying to communicate a Java program with my arduino uno for send orders to the board and read the data sended from it on Java. I'm using the RXTX library ( http://rxtx.qbang.org/wiki/index.php/Download ), version for linux x86_64.
The problem is when i run this example program for learn:
package program;
//Main program class
public class Program
{
//Declares the Arduino object field
public static ArduinoComm myArduino;
//Main method
public static void main(String args[])
{
myArduino = new ArduinoComm();
myArduino.start("/dev/ttyACM0",115200);
myArduino.closeSerialPort();
}
}
package program;
//This class:
// - Starts up the communication with the Arduino.
// - Reads the data coming in from the Arduino and
// converts that data in to a useful form.
// - Closes communication with the Arduino.
//Code builds upon this great example:
//http://www.csc.kth.se/utbildning/kth/kurser/DH2400/interak06/SerialWork.java
//The addition being the conversion from incoming characters to numbers.
//Load Libraries
import java.io.*;
import java.util.TooManyListenersException;
//Load RXTX Library
import gnu.io.*;
class ArduinoComm implements SerialPortEventListener
{
//Used to in the process of converting the read in characters-
//-first in to a string and then into a number.
String rawStr="";
//Declare serial port variable
SerialPort mySerialPort;
//Declare input steam
InputStream in;
boolean stop=false;
public void start(String portName,int baudRate)
{
stop=false;
try
{
//Finds and opens the port
CommPortIdentifier portId = CommPortIdentifier.getPortIdentifier(portName);
mySerialPort = (SerialPort)portId.open("my_java_serial" + portName, 2000);
System.out.println("Serial port found and opened");
//configure the port
try
{
mySerialPort.setSerialPortParams(baudRate,
SerialPort.DATABITS_8,
SerialPort.STOPBITS_1,
SerialPort.PARITY_NONE);
System.out.println("Serial port params set: "+baudRate);
}
catch (UnsupportedCommOperationException e)
{
System.out.println("Probably an unsupported Speed");
}
//establish stream for reading from the port
try
{
in = mySerialPort.getInputStream();
}
catch (IOException e)
{
System.out.println("couldn't get streams");
}
// we could read from "in" in a separate thread, but the API gives us events
try
{
mySerialPort.addEventListener(this);
mySerialPort.notifyOnDataAvailable(true);
System.out.println("Event listener added");
}
catch (TooManyListenersException e)
{
System.out.println("couldn't add listener");
}
}
catch (Exception e)
{
System.out.println("Port in Use: "+e);
}
}
//Used to close the serial port
public void closeSerialPort()
{
try
{
in.close();
stop=true;
mySerialPort.close();
System.out.println("Serial port closed");
}
catch (Exception e)
{
System.out.println(e);
}
}
//Reads the incoming data packets from Arduino.
public void serialEvent(SerialPortEvent event)
{
//Reads in data while data is available
while (event.getEventType()== SerialPortEvent.DATA_AVAILABLE && stop==false)
{
try
{
//-------------------------------------------------------------------
//Read in the available character
char ch = (char)in.read();
//If the read character is a letter this means that we have found an identifier.
if (Character.isLetter(ch)==true && rawStr!="")
{
//Convert the string containing the characters accumulated since the last identifier into a double.
double value = Double.parseDouble(rawStr);
if (ch=='A')
{
System.out.println("Value A is: "+value);
}
if (ch=='B')
{
System.out.println("Value B is: "+value);
}
//Reset rawStr ready for the next reading
rawStr = ("");
}
else
{
//Add incoming characters to a string.
//Only add characters to the string if they are digits.
//When the arduino starts up the first characters it sends through are S-t-a-r-t-
//and so to avoid adding these characters we only add characters if they are digits.
if (Character.isDigit(ch))
{
rawStr = ( rawStr + Character.toString(ch));
}
else
{
//Get the decimal point
if (ch=='.')
{
rawStr = ( rawStr + Character.toString(ch));
}
else
{
System.out.print(ch);
}
}
}
}
catch (IOException e)
{
}
}
}
}
i can't connect to the board and the IDE show me :
run:
Port in Use: gnu.io.NoSuchPortException
java.lang.NullPointerException
BUILD SUCCESSFUL (total time: 1 second)
However, when i start the object "myArduino" with "/dev/ttyS0" (a serial port from the OS) the program run ok and it can connect to the port. This is my output of /dev/tty :
crw-rw---- 1 root dialout 166, 0 2011-05-29 17:58 /dev/ttyACM0
crw-rw---- 1 root dialout 4, 64 2011-05-29 17:48 /dev/ttyS0
Anyone who knows where the problem is?
Thaks all.