在处理草图中将树莓派的蓝牙重新连接到 HC-06

Question

I have a working setup in which a raspberry pi runs a headless processing sketch upon booting. This sketch connects the Pi's onboard bluetooth to an HC-06. The Pi also sets up a serial connection to an arduino nano through a USB cable. The processing sketch acts as a relay. It relays bytes from the arduino to the Hc-06 and vice versa.

The device with the HC-06 is an arduino nano. This device sends out a handshaking signal so the arduino on the Pi's end knows it's connected and sends a respons.

This all works like a charm but on one condition. The Hc-06 needs to be 'on' before the processing sketch boots. If I turn on the HC-06 too late or if I turn it on/off I cannot reconnect and the processing sketch is to be rebooted.

I want to program a more advanced hand shaking protocol with an time-out feature. So both device will be aware that the connection is severed.

I start the processing sketch via a shell script

sudo rfcomm bind hci0 20:14:04:15:23:75
sudo killall java
xvfb-run processing-java --sketch=/home/pi/Documents/bluetooth --run # runs headless

The rfcomm bind command is only yo be run once upon booting.

And the bluetooth script:

import processing.serial.*;


Serial handController;
Serial central;

byte mode;

void setup()
{
    printArray(Serial.list());
    size(200,200);
    background(0); // black

    central = new Serial( this, Serial.list()[3], 115200);
    handController = new Serial( this , Serial.list()[0] , 115200 );
}

long prev;
byte tgl = 0;

void draw()
{

    if(handController.available() > 0) {
        int c = handController.read();
        println("            handcontroller:\t" + (char) c + "\t" + c); // as well char as dec value
        central.write(c);
    }
....

Is it possible that from within this sketch that I terminate the serial connection to rfcomm0 and then restart it?

It seems that this line sets up the bluetooth connection.

handController = new Serial( this , Serial.list()[0] , 115200 ); // rfcomm0

I am not extremely familiar with java. How can I destroy the serial object? And can I do 'new' a 2nd time from out a function?

Kind regards,

Bas

Answer 1

You can use the Serial's stop() method to close the serial connection. You can then re-initialise the port as required.

Here's a rough(untested example):

void restartSerialPort(Serial reference,String portName, int baudRate){
  // pause rendering (draw loop)
  noLoop();
  // stop previous connection
  if(reference != null){
    reference.stop();
    reference = null;
  }
  // start connection anew
  try{
    reference = new Serial( this, portName, baudRate);
  }catch(Exception e){
    println("error opening serial port: " + portName);
    e.printStackTrace();
  }
  // resume rendering
  loop();
}

Bare in mind this needs to be tested/tweaked: I'm not 100% the passed reference will update that easily (otherwise the new Serial object probably needs to be returned by the method and re-assigned to the original reference).

Also not that Processing requires a windowing environment, so it's not quite fully headless.

As a quick alternative to a pure commandline option you can look at Python and the pyserial module