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Contactless Communication API (JSR 257)

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Created: firt (14 Apr 2007)
Last edited: hamishwillee (24 Jul 2013)

Contactless Communication API (JSR 257) defines a Java ME optional package that allows developer to access contactless communication, bi-directional communication and accessing read-only information using differente technologies via short-range wireless means, such as RFID or barcodes, infrared light, or even Bluetooth, and presents such devices via a simple, homogeneous interface to Java applications.

RFID in Brief:

  • RFID (Radio Frequency IDentification) is a technology to carry information over short range by radio waves
  • 13.56 MHz frequency used in mobile devices
  • A tag (transponder) contains digital information in a microchip
  • A reader communicates with a tag
  • Two types of tags
  • Active tag has own power source and longer distance
  • Passive tag gets power from the incoming signal


NFC and NFC Forum

  • NFC (Near Field Communication) specifies simple wireless communication between close coupled devices
  • NFC enables
    • Establishing other types of wireless communication between devices
    • Compatibility with existing contactless smart cards
  • NFC Forum defines common protocols for basic links between NFC enabled devices* NFC Forum Data Exchange Format (NDEF)
    provides vendor independent structure for data

Visual Tags in Brief

  • Optically machine readable information on printed material, typically in the form of bar codes or data matrices
  • Widely used in product identification
  • Symbology defines the features of the visual tag
  • Used character set
  • Encoding and decoding rules
  • Data size
  • Error checking
  • Printing requirements
  • Over 200 known symbologies, only few widely used
  • UPC / EAN / JAN in article numbering

Use Cases for JSR 257

  • Read a URL to movie web page from a tag
  • Store personal shortcuts like phone numbers to a tag
  • Bluetooth or WLAN connection initiation in a multiplayer game with RFID communication* Set device access point settings from a tag
  • Field force on-the-job reporting using RFID tags* Data gathering from RFID tags to a server

Contents

Registering for Target Discovery

//Get DiscoveryManager instance and set TargetListener
//for NDEF_TAG target
DiscoveryManager dm = DiscoveryManager.getInstance();
try {
dm.addTargetListener(this, TargetType.NDEF_TAG);
} catch (ContactlessException ce) {
// handle exception
}

Registering for NDEF - Record Discovery

// Get DiscoveryManager instance and set TargetListener
// for NDEF_TAG and NFC_PEER targets
DiscoveryManager dm = DiscoveryManager.getInstance();
try {
NDEFRecordType recordType = new NDEFRecordType(NDEFRecordType.NFC_FORUM_RTD, "MyOwnType");
dm.addNDEFRecordListener(this, recordType);
} catch (. . .) {
// handle exception
}


Making a Connection to the Target

public void targetDetected(TargetProperties[] prop) {
// Select first target
TargetProperties target = prop[0];
try {
// NDEF_TAG target found
String url = target.getUrl();
// Open NDEFTagConnection to the target
conn = (NDEFTagConnection)Connector.open(url);
// Read data from the target
NDEFMessage message = conn.readNDEF();
NDEFRecord[] records = message.getRecords();
} catch (. . .) {}
 
}


Receive Read-Only Data from NDEF Tag

public class MyMIDlet extends MIDlet implements NDEFRecordListener {
 
public void recordDetected(NDEFMessage ndefMessage) {
NDEFRecord[] records = ndefMessage.getRecords();
for (int i=0; i<records.length; i++) {
// Handle data
}
}
}

Read Visual Tag Image

public void readVisualTag() {
checkReadSymbologySupport();
try {
String[] images = SymbologyManager.getImageClasses();
// Open connection to visual tag
VisualTagConnection conn = (VisualTagConnection)
Connector.open("vtag://");
String data = conn.readVisualTag(getImage(), images[0], mySymbology);
// Handle data from the image
conn.close();
} catch (. . .) {
// handle exception
}
}

Generate Visual Tag Image

public void generateVisualTag() {
checkReadSymbologySupport();
try {
// Get properties for symbology
ImageProperties properties = SymbologyManager.getImageProperties("code-39");
String imageClass = getImageClass();
VisualTagConnection conn = (VisualTagConnection)
Connector.open("vtag://");
// Generate visual tag image
Object vtagImage = conn.generateVisualTag("test", imageClass, properties);
. . .
} catch (. . .) {
// handle exception
}
}


Summary

  • JSR 257 offers communication to various contactless targets
  • Can be extended to cover future contactless targets
  • Provides general discovery mechanism
  • Eases tasks of the application developer
  • Supports MIDP push mechanism for automatic application launch for NDEF formatted data
  • Flexible design and minimal set of mandatory features
  • Allows implementations to support only RFID tags or visual tags or both

More Information

This page was last modified on 24 July 2013, at 08:07.
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