Hi guys, i'm communicating Arduino with Java by serial.
I can write something in java and read in Arduino, but when i do the opposite a strange error happens: I need to open the serial monitor and then read in java. The problem is that I need to send something when I press a button and it is not possible to open the serial monitor while the program ( java ) is running . Why it's happening?
My Arduino is Leonardo.
My Arduino Code:
int ledPin = 7;
int btn = 2;
int dado;
String palavra;
void setup(){
Serial.begin(9600);//frequência da porta serial
pinMode(ledPin,OUTPUT);
pinMode(btn,INPUT);
}
void loop(){
if(Serial.available() > 0){
dado = Serial.read();
palavra=palavra+dado;
switch(dado){
case 'a':
digitalWrite(ledPin,HIGH);
break;
case 'b':
digitalWrite(ledPin,LOW);
break;
}
}
//if (digitalRead(btn)==HIGH){
Serial.write("oi");
// }
}
My java code:
package nulltest;
// derived from SUN's examples in the javax.comm package
import java.io.*;
import java.util.*;
//import javax.comm.*; // for SUN's serial/parallel port libraries
import gnu.io.*; // for rxtxSerial library
public class nulltest implements Runnable, SerialPortEventListener {
static CommPortIdentifier portId;
static CommPortIdentifier saveportId;
static Enumeration portList;
InputStream inputStream;
SerialPort serialPort;
Thread readThread;
static String messageString = "a";
static OutputStream outputStream;
static boolean outputBufferEmptyFlag = false;
public static void main(String[] args) {
boolean portFound = false;
String defaultPort;
// determine the name of the serial port on several operating systems
String osname = System.getProperty("os.name","").toLowerCase();
if ( osname.startsWith("windows") ) {
// windows
defaultPort = "COM7";
} else if (osname.startsWith("linux")) {
// linux
defaultPort = "/dev/ttyUSB0";
} else if ( osname.startsWith("mac") ) {
// mac
defaultPort = "????";
} else {
System.out.println("Sorry, your operating system is not supported");
return;
}
if (args.length > 0) {
defaultPort = args[0];
}
System.out.println("Set default port to "+defaultPort);
// parse ports and if the default port is found, initialized the reader
portList = CommPortIdentifier.getPortIdentifiers();
while (portList.hasMoreElements()) {
portId = (CommPortIdentifier) portList.nextElement();
if (portId.getPortType() == CommPortIdentifier.PORT_SERIAL) {
if (portId.getName().equals(defaultPort)) {
System.out.println("Found port: "+defaultPort);
portFound = true;
// init reader thread
nulltest reader = new nulltest();
}
}
}
if (!portFound) {
System.out.println("port " + defaultPort + " not found.");
}
}
public void initwritetoport() {
// initwritetoport() assumes that the port has already been opened and
// initialized by "public nulltest()"
try {
// get the outputstream
outputStream = serialPort.getOutputStream();
} catch (IOException e) {}
// try {
// // activate the OUTPUT_BUFFER_EMPTY notifier
// serialPort.notifyOnOutputEmpty(true);
// } catch (Exception e) {
// System.out.println("Error setting event notification");
// System.out.println(e.toString());
// System.exit(-1);
// }
}
public void writetoport() {
System.out.println("Writing \""+messageString+"\" to "+serialPort.getName());
try {
// write string to serial port
outputStream.write(messageString.getBytes());
} catch (IOException e) {}
}
public nulltest() {
// initalize serial port
try {
serialPort = (SerialPort) portId.open("SimpleReadApp", 2000);
} catch (PortInUseException e) {}
try {
inputStream = serialPort.getInputStream();
} catch (IOException e) {}
try {
serialPort.addEventListener(this);
} catch (TooManyListenersException e) {}
// activate the DATA_AVAILABLE notifier
serialPort.notifyOnDataAvailable(true);
try {
// set port parameters
serialPort.setSerialPortParams(9600, SerialPort.DATABITS_8,
SerialPort.STOPBITS_1,
SerialPort.PARITY_NONE);
} catch (UnsupportedCommOperationException e) {}
// start the read thread
readThread = new Thread(this);
readThread.start();
}
public void run() {
// first thing in the thread, we initialize the write operation
initwritetoport();
try {
while (true) {
// write string to port, the serialEvent will read it
writetoport();
Thread.sleep(1000);
}
} catch (InterruptedException e) {}
}
public void serialEvent(SerialPortEvent event) {
switch (event.getEventType()) {
case SerialPortEvent.BI:
case SerialPortEvent.OE:
case SerialPortEvent.FE:
case SerialPortEvent.PE:
case SerialPortEvent.CD:
case SerialPortEvent.CTS:
case SerialPortEvent.DSR:
case SerialPortEvent.RI:
case SerialPortEvent.OUTPUT_BUFFER_EMPTY:
break;
case SerialPortEvent.DATA_AVAILABLE:
// we get here if data has been received
byte[] readBuffer = new byte[20];
try {
// read data
while (inputStream.available() > 0) {
int numBytes = inputStream.read(readBuffer);
}
// print data
String result = new String(readBuffer);
System.out.println(result);
} catch (IOException e) {}
break;
}
}
}
Thanks, help me if possible.