Arduino + Bluetooth module Help

Question

Does anyone know how to connect the DF Robot Bluetooth module up to the arduino and get it to communicate with the software?

I used this tutorial.

I managed to get the light flashing on the module and it seems to be able to pair fine but when I run the serial monitor and send a letter (say 'H') which should turn a light on I get a Java error:

java.io.IOException: Bad file descriptor in nativeDrain 
    at gnu.io.RXTXPort.nativeDrain(Native Method)
at gnu.io.RXTXPort$SerialOutputStream.flush(RXTXPort.java:1201)
at processing.app.Serial.write(Serial.java:470)
at processing.app.Serial.write(Serial.java:492)
at processing.app.SerialMonitor.send(SerialMonitor.java:128)
at processing.app.SerialMonitor.access$100(SerialMonitor.java:29)
at processing.app.SerialMonitor$4.actionPerformed(SerialMonitor.java:82)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

I checked the wiring and I have the RXD going to the RX (pin 0) on the board and TXD to TX(pin 1) and the rest wired up, but again still no luck. Anyone have any thoughts?

This is also the code I have on the arduino:

int ledpin = 13;
char val;
void setup() {
    pinMode(ledpin, OUTPUT); // pin 48 (on-board LED) as OUTPUT
    Serial.begin(9600); // start serial communication at 9600bps
}

void loop() {
    if( Serial.available() ) { // if data is available to read
        val = Serial.read(); // read it and store it in 'val'
    }

    if( val == 'H' ) { // if 'H' was received
        digitalWrite(ledpin, HIGH); // turn ON the LED
    } else {
        digitalWrite(ledpin, LOW); // otherwise turn it OFF
    }

    delay(100); // wait 100ms for next reading
}

Answer 1

I've had similar troubles in establishing communication from PC to GSM Modem via serial port. I was first working with java.comm on vista and it was impossible. Later, I switched to RxTxComm and it was a lot more reliable. Use it instead.

Answer 2

Try to upgrade your RXTX library to the latest version. IIRC the Arduino IDE comes bundled with a version of it.

Answer 3

This is a long shot, but...

The example in the linked tutorial uses a baud rate of 115200 (rather than the 9600 used in your example) and says:

Check the serial setting! Make sure the baud rate is set to 115200 on both master and slave.

It could be that either:

• This only works with a baud rate of 115200 (which seems unlikely) or possibly
• The baud rate on the master and slave is not 9600

Answer 4

It's possible that a dodgy power supply to the Arduino/Bluetooth module could cause this error (i.e. it could be related to the error reported in this Arduino Forum Topic).