The canvas with the van is not very nice, but just to show you a demo of the spray can. sorry for my bad spraying skills. see a description of the project here.

I did this demo video earlier this year while developing the spray can for my thesis project. The RGB LED wasn’t bright enough so I replaced it with a super bright one later on and moved it to the top of the can to lighten up the donut.

In order to receive tags, the RFID reader has to be activated through a click on the image. After that, the different RFID tags (sorry for my tiny tags) are used to create different forms.

The previous post was all about wiring the RFID reader ID-12 and an Arduino board. Now I want to show you how to use this setup within an ActionScript application.

As you don’t have the possibility to access the hardware respectively the usb/bluetooth serial port directly, you have to use a Socket server which redirects the network socket connections to or from the serial ports. Fortunately there are already ready-to-use solutions like serproxy or TinkerProxy (win, osx) available. Personally I prefer serproxy, but if you want to have a nice GUI I would recommend TinkerProxy.
These proxy servers are not made specifically for the use with Flash and therefore they don’t implement a cross-domain-policy file. As you probably know this is needed for not getting a security error in your flash application. As a workaround for that problem you can get lessrains policyserver and start it on port 5334 (java -jar policyserver.jar 5334). It will return an appropriate policy file when requested by the flash application.

With these things in mind we can go for some code now.

...
public function connect() : void
{
	if(_state != DISCONNECTED) return;
	_state = CONNECTING;
 
	addSocketEvents();
 
	// load policy file from localhost, port 5334
	Security.loadPolicyFile("xmlsocket://" + SOCKET_HOST + ":" + String(POLICY_PORT));
	// connect to proxy localhost, port 5333
	_socket.connect(SOCKET_HOST, PROXY_PORT);
}
 
public function disconnect() : void
{
	if(_state != CONNECTED) return;
	_state = DISCONNECTING;
 
	sendDisconnect();
	processDisconnect();
}
 
public function finalize() : void
{
	...
}
...

My RFID class implements basically 3 public methods + the EventDispatcher stuff.

...
private function connectSocket(event : Event) : void 
{   
	// send ping to arduino
	_pingTimer = new Timer(100, 0);
	_pingTimer.addEventListener(TimerEvent.TIMER, handleTimer);
	_pingTimer.start();
}
 
private function handleTimer(event : TimerEvent) : void
{
	sendPing();
}
...

The Socket class dispatches Event.CONNECT when the connection to the proxy server is established but that doesn’t mean that the hardware is connected as well. To really know when the arduino is listening I use a timer to send a ping to the Arduino board. When I get the ping back, I know that the Arduino is ready to use.

...
private function processRfidTag() : void
{
	_cachePosition = _cache.position - 1;
	var bytesIn : int = 0;
	var val : int;
	var rfidTag : String = "";
 
	while (_cache.bytesAvailable > 0 && bytesIn < 10) 
	{                        				
		val = _cache.readByte();
 
		// if ETX or STX before the 10 digit reading -> stop reading
		if((val == STX) || (val == ETX)) break;
 
		// Do Ascii/Hex conversion:
		if ((val >= 0x30) && (val < = 0x39)) 
			val -= 0x30;
		else if ((val >= 0x41) && (val < = 0x46))
			val = 10 + val - 0x41;
 
		rfidTag += val.toString(16).toUpperCase();
 
		// ready to read next digit
		bytesIn++;                                
	}
 
	// read complete
	if (bytesIn == 10) 
	{ 
		if(rfidTag != "0000000000" ) _tag = rfidTag;
		else _tag = null;
 
		_cachePosition = -1;
		dispatchEvent(new RFIDEvent(RFIDEvent.TAG_CHANGED));
	}
}
...

When I receive some data from the socket, I look for the STX byte which is the header or marker of the RFID tag and get the tag via processRfidTag(). Beyond that I don’t read the bytes directly from the socket but write all the incoming data in a cache first to not loose any information coming in in different ProgressEvent.SOCKET_DATA events.

Download the full source of my ID-12 demo and don't forget to replace my tag ids with yours otherwise your RFID tags won't draw any form.

There are basically 2 major differences in comparison to other implementations:

1. software serial
The ID-12 uses a serial connection to send the tags. All the other implementations are using the hardware serial pin (RX) to retrieve the information and send it to the computer. The problem of this setup with the ID-12 blocking the receive pin is that you can’t send any data from the computer to the arduino board anymore. This implementation is using a software serial connection on an other I/O pin in order to maintain bidirectional communication.

2. RFID tag removed
The ID-12 has no native method to determine whether a RFID tag is still in range or has been removed already. With a little workaround you can get this information as well.

but enough talking, get this thing started:

Wiring

Connect pin 11 to +5V, 1 and 7 to ground, 2 and 9 to Arduino pins 4 and 5;

Arduino code

First of all you have to get the AF_SoftSerial library (you will need an Arduino board with an ATmega168) or NewSoftSerial (for ATmega328). Uncompress and place it in the hardware/library directory under your Arduino software installation.

After installing the AFSoftSerial library you can download my arduino code and upload it to your board. I don’t want to go through the code in detail, you can always leave a comment or get in touch with me if you have problems with it.

...
void loop () 
{
  byte action = 0;
  unsigned int now = millis();
 
  updateID12(false);
 
  // connection to computer established
  if(connected == true)
  {
    clearTag(rfidTagTemp, 6);
 
    // serial connection with rfid reader
    if (rfidSerial.available()) 
    {
      // wait for the next STX byte
      while(rfidSerial.available() && action != 0x02)
        action = rfidSerial.read();
 
      // STX byte found -> RFID tag available
      if(action == 0x02)
      {
        if(readID12(rfidTagTemp))
        {
          nowLastRfid = millis();
          rfidTagSeen = true;
          updateCurrentRfidTag(rfidTagTemp);
        }
      }
 
    }
    else if(rfidEnabled && rfidTagSeen == true && (now - nowLastRfid) >= RFID_REMOVED_TIME)
    {    
      rfidTagSeen = false;
      updateCurrentRfidTag(rfidTagTemp);
    }
  }
 
  // serial connection with computer
  while (Serial.available() > 0) 
  {
    // read action byte
    action = Serial.read();
 
    switch (action) 
    {
      // PING
      case 0x01:
        Serial.print(0x01, BYTE);
 
      // (C)ONNECT
      case 0x43:
        // clear serial
        while(rfidSerial.available()) rfidSerial.read();
        connected = true;
        break;
 
      // (D)ISCONNECT
      case 0x44:
        connected = false;
        break;
    }
  }
 
  // delay 100 milliseconds
  delay(100);
}
....

The first part of the code is for reading the RFID tags and checking if the tag is still in the range of the reader.

The second part handles the communication with the computer. You can define specific bytes as marker and accordingly get the value of different sensors, execute functions on the hardware or whatever you want, e.g. in order to use the RFID reader and get an output of the RFID tags on your console you have to send the connect marker which is a "C" or 0×43 in hex.

Update 08.02.2010 – Fix for the Atmega 328 chip

Finally a fix for the Duemilanove (which is using an Atmega 328 chip). There is a new Sofware Serial Library out there which works with the Duemilanove, it’s called NewSoftSerial. Just use this library instead of the old one and everything should work. Thanks Thijs for the information

VandalSpray features includes:

• exchangeable caps
• color display
• digital valve system to vary the amount of »paint« coming out of the cap
• different colors
• wireless

The spray can is built upon the Arduino platform and uses different sensors and electronic modules like a RFID reader, a super bright RGB LED, a Rotary Encoder, a Bluetooth module, a force sensitive resitor (FSR) and loads of wires and solder to implement the desired behavior. For tracking the spray can I use a Wiimote and the WiiFlash ActionScript 3 library and server, but this could also be replaced by a standard webcam and an adequate tracking implementation.
Because I didn’t want to put some kind of speaker in the spray can (there was no space left anyway) the spray sound is generated from the AIR app and output on the speakers of the notebook.

VandalSpray vs. Montana spray can

VandalSpray electronics

More
http://blog.formatlos.de/2008/12/12/digital-spraycan-edemo/
http://blog.formatlos.de/2008/12/19/digital-graffiti-spray-demo/

First of all you should get an easy-to-use prototyping platform like arduino (http://arduino.cc/), wiring (http://wiring.org.co), freeduino (http://www.freeduino.org/) … the arduino board is not very expensive and there are a lot of tutorials how to use it and how to connect other hardware to it.

getting started with electronics and arduino:

• Learn Electronics using Arduino (http://www.ladyada.net/learn/arduino/)
  
• Tutorials in german (http://www.physical-computing.de/)
• Tutorials by the Stanford HCI Group (http://protolab.pbwiki.com/)
• ITP Physical Computing (http://itp.nyu.edu/physcomp/)
• Tom Igoe (http://www.tigoe.net/pcomp/)

another good source of inspiration is flickr. just search for »arduino« and you’ll find a lot of cool projects, links and working circuits.