Windows 8 Platform NFC Development

Windows 8 PlatformNFC Development

Andreas Jakl, Mopius

Andreas JaklTwitter: @mopius

Email: andreas.jakl@mopius.com

Trainer & app developer– mopius.com

– nfcinteractor.com

Nokia: Technology Wizard

FH Hagenberg, Mobile Computing: Assistant Professor

Siemens / BenQ Mobile: Augmented Reality-Apps

Based on MSDN documentationbit.ly/ProximityAPIbit.ly/ProximityAPIwp8bit.ly/ProximitySpec

We’re coveringWindows (Phone) 8 Proximity APIs

Tap and Do

A gesture that is a natural interaction between people in close proximity used to trigger doing something together between the devices they are holding.

System: Near Field Proximity(e.g., NFC)

Documentation: bit.ly/ProximitySpec

NFC Scenarios

Connect Devices Exchange Digital Objects Acquire Content

ACQUIRE CONTENTFrom Tags and Peers

Acquire Content Scenarios

Website link (e.g., company)

More information (e.g., museum, concert)

Custom app extensions (e.g., bonus item for a game)

Angry Birds © Rovio

LaulujoutsenWhooper SwanNational bird of Finland, on €1 coin

Get Started: Read URIs via NFC

ProximityDeviceConnect to HWDetect devices in rangePublish & subscribe to messages

ProximityMessageContents of received message

Proximity Capability

URI Subscriptions

_device = ProximityDevice.GetDefault();

_subscribedMessageId = _device.SubscribeForMessage("WindowsUri", MessageReceivedHandler);

1 Activate proximity device

2 Subscribe to URI messages

3 Handle messagesprivate void MessageReceivedHandler(ProximityDevice sender,

ProximityMessage message) {var msgArray = message.Data.ToArray();var url = Encoding.Unicode.GetString(msgArray, 0, msgArray.Length);Debug.WriteLine("URI: " + url);

API documentation: bit.ly/ProximityAPI

URI Subscriptions

_subscribedMessageId = _device.SubscribeForMessage(…);

_device.StopSubscribingForMessage(_subscribedMessageId);

WindowsUriSmart Poster

4 Cancel subscriptions

SPREAD THE WORDPublish & Write

Publish Messages

Proximity devices only

– (doesn’t write tags)

Windows Protocol + URI record

– Encapsulated in NDEF

_publishingMessageId = _device.PublishUriMessage(new Uri("nfcinteractor:compose"));

1 Start publishing

Contains scheme,

platform & App ID

Write Tags

1 Prepare & convert datavar dataWriter =

new Windows.Storage.Streams.DataWriter { UnicodeEncoding = Windows.Storage.Streams.

UnicodeEncoding.Utf16LE};

dataWriter.WriteString("nfcinteractor:compose");var dataBuffer = dataWriter.DetachBuffer();

2 Write tag (no device publication)_device.PublishBinaryMessage("WindowsUri:WriteTag", dataBuffer);

Mandatory encoding

bit.ly/PublishTypes

Tag Size?

1 Subscribe for writable tag info_device.SubscribeForMessage("WriteableTag", MessageReceivedHandler);

2 Check maximum writable tag size in handlervar tagSize = BitConverter.ToInt32(message.Data.ToArray(), 0);Debug.WriteLine("Writeable tag size: " + tagSize);

3 Device HW capabilitiesvar bps = _device.BitsPerSecond; // >= 16kB/svar mmb = _device.MaxMessageBytes; // >= 10kB

NDEF HANDLINGStandardized NFC Tag Contents

Data on an NFC Tag

Stored onNFC Forum Tag

Encapsulated inNDEF Message

Encoded throughNFC Forum

Tag Type Platform

DataNDEF Record(s)

[speech text]

{0450eab3-92…}

Arguments

WindowsPhone app ID

LaunchApp

NDEF = NFC Data Exchange Format, Container image adapted from s_volenszki (Flickr), released under Creative Commons BY-NC 2.0

Reading NDEF

_subscribedMessageId = _device.SubscribeForMessage("NDEF", MessageReceivedHandler);

1 Subscribe to all NDEF messages

2 Parse raw byte array in handler

http://www.nfc-forum.org/specs/

_subscribedMessageId = _device.SubscribeForMessage("NDEF", MessageReceivedHandler);

Subscribe to all NDEF messages

Parse raw byte array in handler

http://www.nfc-forum.org/specs/

// Convert the language code to a byte arrayvar languageEncoding = Encoding.UTF8;var encodedLanguage = languageEncoding.GetBytes(languageCode);// Encode and convert the text to a byte arrayvar encoding = (textEncoding == TextEncodingType.Utf8) ? Encoding.UTF8 : Encoding.BigEndianUnicode;var encodedText = encoding.GetBytes(text);// Calculate the length of the payload & create the arrayvar payloadLength = 1 + encodedLanguage.Length + encodedText.Length;Payload = new byte[payloadLength];

// Assemble the status bytePayload[0] = 0; // Make sure also the RFU bit is set to 0// Text encodingif (textEncoding == TextEncodingType.Utf8)

Payload[0] &= 0x7F; // ~0x80else

Payload[0] |= 0x80;

// Language code lengthPayload[0] |= (byte)(0x3f & (byte)encodedLanguage.Length);

// Language codeArray.Copy(encodedLanguage, 0, Payload, 1, encodedLanguage.Length);

// TextArray.Copy(encodedText, 0, Payload, 1 + encodedLanguage.Length, encodedText.Length);Si

Reading NDEF

NFC / NDEF LIBRARY FOR PROXIMITY APISWindows 8 & Windows Phone 8

NDEF.codeplex.com

Reusable NDEF classes

Create NDEFmessages & records

(standard compliant)

Parse informationfrom raw byte arrays

Fully documentedOpen Source LGPL license

(based on Qt Mobility)

NDEF Subscriptions

_subscribedMessageId = _device.SubscribeForMessage("NDEF",MessageReceivedHandler);

1 Subscribe to all NDEF formatted tags

private void MessageReceivedHandler(ProximityDevice sender, ProximityMessage message){

var msgArray = message.Data.ToArray();NdefMessage ndefMessage = NdefMessage.FromByteArray(msgArray);[...]

2 Parse NDEF message

NDEF Subscriptions

foreach (NdefRecord record in ndefMessage) {

Debug.WriteLine("Record type: " + Encoding.UTF8.GetString(record.Type, 0, record.Type.Length));

// Check the type of each record ‐ handling a Smart Poster in this exampleif (record.CheckSpecializedType(false) == typeof(NdefSpRecord)) {

// Convert and extract Smart Poster infovar spRecord = new NdefSpRecord(record);Debug.WriteLine("URI: " + spRecord.Uri);Debug.WriteLine("Titles: " + spRecord.TitleCount());Debug.WriteLine("1. Title: " + spRecord.Titles[0].Text);Debug.WriteLine("Action set: " + spRecord.ActionInUse());

3 Analyze all contained NDEF records with specialized classes

Write NDEF

1 Prepare & convert data// Initialize Smart Poster record with URI, Action + 1 Titlevar spRecord = new NdefSpRecord

{ Uri = "http://www.nfcinteractor.com" };spRecord.AddTitle(new NdefTextRecord

{ Text = "Nfc Interactor", LanguageCode = "en" });

// Add record to NDEF messagevar msg = new NdefMessage { spRecord };

2a Write tag// Publish NDEF message to a tag_device.PublishBinaryMessage("NDEF:WriteTag", msg.ToByteArray().AsBuffer());

2b Publish to devices// Alternative: send NDEF message to another NFC device_device.PublishBinaryMessage("NDEF", msg.ToByteArray().AsBuffer());

APP LAUNCHING

App Launch Scenarios

Discover your app

Share app to other users

Create seamless multi-user experience

Register for

App Launching Summary

User opensparticular file

URI protocol

Tag launches appthrough custom

URI scheme

LaunchApp Tag

Tag directly containsapp name and

parameters

Peer to Peer

App requests peerdevice to startthe same app

Not so relevant for NFC

How to Launch Apps

Custom URI schemelaunches app.App needs to register.

Tag directly containsapp name andcustom data.No registration necessary.

Win8 + WP8

nearspeak: Good+morning.Custom data

Protocol name

Encoded Launch URI

Examples*skype:mopius?call

spotify:search:17th%20boulevard

* Definition & examples: http://en.wikipedia.org/wiki/URI_scheme

User Experience

No app installed 1 app installed 2+ apps installed

WP Protocol Association

1 Specify protocol name in WMAppManifest.xml

...</Tokens><Extensions><Protocol Name="nearspeak"

NavUriFragment="encodedLaunchUri=%s"TaskID="_default" />

</Extensions>

Protocol name

Note: different in Win8 / WP8

2 Create UriMapper class to parse parametersclass NearSpeakUriMapper : UriMapperBase{

public override Uri MapUri(Uri uri){

// Example: "Protocol?encodedLaunchUri=nearspeak:Good+morning."var tempUri = HttpUtility.UrlDecode(uri.ToString());var launchContents = Regex.Match(tempUri, @"nearspeak:(.*)$").Groups[1].Value;if (!String.IsNullOrEmpty(launchContents)){

// Launched from associated "nearspeak:" protocol// Call MainPage.xaml with parametersreturn new Uri("/MainPage.xaml?ms_nfp_launchargs=" + launchContents, UriKind.Relative);

// Include the original URI with the mapping to the main pagereturn uri;

}} Argument already handled in step 9 of LaunchApp tags (MainPage.OnNavigatedTo)

3 Use UriMapper in App.xaml.cs(region: )

private void InitializePhoneApplication() {RootFrame = new PhoneApplicationFrame();RootFrame.UriMapper = new NearSpeakUriMapper();

– If needed: launch protocol from app (for app2app comm)

await Windows.System.Launcher.LaunchUriAsync(new Uri("nearspeak:Good+morning."));

Windows 8 Protocol Association

Directly launch App

parameters app name 1platform 1 platform 2 app name 2 …

* For your low-level interest: type: Absolute URI, type name format: windows.com/LaunchApp. Contents re-formatted, e.g., with string lengths before each value

Encoded into NDEF message*

Write LaunchApp Tags

var launchArgs = "user=default"; // Can be empty// The app's product id from the app manifest, wrapped in {}var productId = "{xxx}"; var launchAppMessage = launchArgs + "\tWindowsPhone\t" + productId;

var dataWriter = new Windows.Storage.Streams.DataWriter{UnicodeEncoding = Windows.Storage.Streams.UnicodeEncoding.Utf16LE};

dataWriter.WriteString(launchAppMessage);

1 Launch parameters, platforms + app IDs (note: Win8/WP8 ID format differences)

2 Convert to byte array

3 Write to tags_device.PublishBinaryMessage("LaunchApp:WriteTag",

dataWriter.DetachBuffer());

PEER TO PEER

Tap for

Quick Data Exchange

ProximityDeviceExchange Windows /

NDEF messages,SNEP protocol

Long Term Connection

PeerFinderAutomatically builds

Bt / WiFi Directsocket connection

Seamless Multi-User Games & Collaboration

Establishing

Long Term Connection

Trigger

Interact with TapNFC

Browse

Start SearchBt, WiFi, etc.

Tap to Trigger

App not installed

App installed

Connection State

PeerFound

1Proximity gesture completeDevices can be pulled away

Connecting /Listening

2Which device initiated tap gesture?→ Connecting, other device Listening

Completed

3Access socket of persistent transport

(e.g., TCP/IP, Bt)

Find Peers

PeerFinder.TriggeredConnectionStateChanged +=TriggeredConnectionStateChanged;

PeerFinder.Start();

1 Start waiting for triggered connections

2 Peer found & connection established? Send message over socket

* For URI records + simple Smart Poster (w/o title), use the WindowsUri type.

private async void TriggeredConnectionStateChanged(object sender, TriggeredConnectionStateChangedEventArgs eventArgs) {

if (eventArgs.State == TriggeredConnectState.Completed) {// Socket connection established!var dataWriter = new DataWriter(eventArgs.Socket.OutputStream);dataWriter.WriteString("Hello Peer!");var numBytesWritten = await dataWriter.StoreAsync();

}}Completed

UX Recommendations*

User initiated peer search only Ask for consent Show connection

Failed connection?

Inform & revert to single-user mode

Let user get out of proximity

experience

Proximity: only if connection details

not relevant

NFC ToolsProximity Tapper for WP emulator

– http://proximitytapper.codeplex.com/

Open NFC Simulator

– http://open-nfc.org/wp/editions/android/

NFC plugin for Eclipse: NDEF Editor

– https://code.google.com/p/nfc-eclipse-plugin/

nfcinteractor.com

NFC Resources NFC News: nfcworld.com

NFC developer comparison

(WP, Android, BlackBerry):

bit.ly/NfcDevCompare

Specifications: nfc-forum.org

Thank You.

Andreas Jakl@mopius

mopius.comnfcinteractor.com

Windows 8 Platform NFC Development

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