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Building a Sensor Network Controller Michael Pigg Chariot Solutions November 5, 2010 This work is licensed under the Creative Commons Attribution- Noncommercial-Share Alike 3.0 United States License. Friday, November 5, 2010 1 Chariot

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Building a Sensor Network Controller

Michael Pigg Chariot Solutions

November 5, 2010

This work is licensed under the Creative Commons Attribution- Noncommercial-Share Alike 3.0 United States License.

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Chariot Solutions

Practical, smart software development powered by Java, open source and emerging technologies

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Agenda

  • What are we building?
  • Why use OSGi?
  • Look at interesting code features
  • Run the system

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An engineer* walks into a room ...

*Software guy with old, dusty electrical technology degree, really

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and notices it’s too cold.

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He walks into another and notices it’s too warm.

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Hire someone to fix it?

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No Way!

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Build a system to monitor temperature in multiple rooms.

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What should it do?

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Collect temperature data from multiple locations

Requirements

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Record data for later analysis

Requirements

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No wires

Requirements

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Easily add new capabilities

Requirements

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Proposed Solution

  • Hardware
  • Custom wireless sensor module
  • Software
  • Controller software based on Apache

Felix

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Why OSGi and Felix?

  • Highly modular architecture
  • Capable of being updated at runtime
  • Already implemented solutions
  • console shell commands
  • configuration implementation
  • web-based configuration UI

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Hardware

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Sensor Module

  • Digi XBee wireless mesh network module
  • Has integrated ADC
  • Operates in voltage range of 2 AA batteries
  • Relatively low power consumption

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Vref Wireless Module Temp Sensor

(under board)

Professional Wiring* Super Soldering Job*

Text

*Not so much

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Life of a Node

  • Sleep for 5 minutes, then wake up
  • Sample ADC port
  • Send sample data over network
  • Go back to sleep

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XBee

USB

XBee XBee XBee XBee

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Software

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XBee Communication

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Connect XBee to PC

  • XBee to USB
  • Appears as serial port

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XBee has custom protocol

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XBeeLib

  • Implementation of XBee API protocol
  • Open source, BSD license
  • http://kenai.com/projects/xbeelib

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Apache Mina

  • Eases implementation of custom protocol

encoder/decoder

  • Support for fragmented packets
  • Comes with serial port transport

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XbeeLib Config Admin Metatype Service

ManagedServiceFactory metatype.xml XBeeService xb xbr xbconfig

Mina Core RXTX Mina Serial

Indirect Exported Packages

XBee USB

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RXTX requires native library

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Where to put native library?

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How to get native library installed?

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Bundle-NativeCode

  • Parameters
  • path to native code in bundle JAR
  • osname (MacOS, Linux, etc.)
  • processor (x86, PowerPC, etc.)
  • osversion

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<plugin> <groupId>org.apache.felix</groupId> <artifactId>maven-bundle-plugin</artifactId> <version>2.0.1</version> <extensions>true</extensions> <configuration> <instructions> <Import-Package>*</Import-Package> <Export-Package>net.michaelpigg.xbeelib.protocol,net.michaelpigg.xbeelib</Export-Package> <Embed-Dependency>rxtx,mina-transport-serial</Embed-Dependency>

<Bundle-NativeCode>lib/rxtx/mac/x86_64/

librxtxSerial.jnilib; osname=MacOSX; processor=x86_64</Bundle- NativeCode>

<Bundle-Activator>net.michaelpigg.xbeelib.impl.BundleActivator</Bundle-Activator>

</instructions> </configuration> </plugin>

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XBeeLib dependencies

  • Mina and most other dependencies are

deployed as bundles

  • Mina serial transport and RXTX are

embedded into XBeeLib bundle

  • RXTX is not OSGi-ready
  • Mina serial depends on RXTX

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<plugin> <groupId>org.apache.felix</groupId> <artifactId>maven-bundle-plugin</artifactId> <version>2.0.1</version> <extensions>true</extensions> <configuration> <instructions> <Import-Package>*</Import-Package> <Export-Package>net.michaelpigg.xbeelib.protocol,net.michaelpigg.xbeelib</Export-Package>

<Embed-Dependency>rxtx,mina-transport-serial</Embed- Dependency>

<Bundle-NativeCode>lib/rxtx/mac/x86_64/librxtxSerial.jnilib; osname=MacOSX; processor=x86_64</Bundle- NativeCode>

<Bundle-Activator>net.michaelpigg.xbeelib.impl.BundleActivator</Bundle-Activator>

</instructions> </configuration> </plugin>

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First Contact

  • XBeeLib provides simple shell commands

for sending commands to XBee modules

  • xb - send command to local XBee
  • xbr - send command to remote XBee

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Shell Commands

  • Felix provides the Gogo shell as of 3.0
  • Bundles contribute commands by

registering a service with two properties

  • osgi.command.scope
  • osgi.command.function

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public void start(BundleContext context) throws Exception { Hashtable cmdProps = new Hashtable(); // these commands are in scope “xbee” cmdProps.put(CommandProcessor.COMMAND_SCOPE, “xbee”); // “xb” and “xbr” are functions that can act as commands cmdProps.put(CommandProcessor.COMMAND_FUNCTION, new String[] {“xb”, “xbr”}); context.registerService( ToXbeeCommand.class.getName(), new ToXbeeCommand(context), cmdProps); }

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g! help felix:bundlelevel ..... felix:which gogo:cat .... gogo:until

  • br:deploy

....

  • br:source

xbee:listports xbee:xb xbee:xbconfig xbee:xbr xbee:xmon xbee:xsample g!

Listing Shell Commands

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Using Commands

g! xb nd ND response: Frame ID = 109;Status = OK;Address = 0013a200403c5e93;Signal strength = 32; g! x1 = "0013a200403c5e93" 0013a200403c5e93 g! xbr $x1 is IS response: Frame ID = 11;Status = OK;Data: 010200013c g!

Send node discover command Request sample

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Transform Data

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Incoming Data

  • Number resulting from ADC sample on

XBee

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XbeeAnalogData Transformer Interface

  • Implementations convert raw ADC reading

to useful data

  • TemperatureSensorTransformer does this

for our temperature sensor hardware

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xbee-temp-sensor bundle

xbee- listener temp- sensor

XbeeAnalogDataTransfomer

Config Admin

ManagedServiceFactory

Metatype

metatype.xml

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Sample with no Transformer

g! xsample $x1 Command returned with status OK Raw data in response:1200dd Number of samples 1 Digital I/O No digital I/O data in response. Analog Data 1: DD(221) g!

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Configuring Temperature Sensors

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Config file?

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NO!

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Configuration Admin Service

  • Stores configuration for a service
  • Sends configuration to service
  • at startup
  • when configuration changes

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ManagedService or ManagedServiceFactory?

  • ManagedService
  • Configures at most one instance
  • ManagedServiceFactory
  • Configures one or more instances

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We need to configure multiple sensors

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Implementation

  • Make up a PID
  • Implement ManagedServiceFactory
  • Register implementation as a service with

the chosen PID

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public class XbeeTemperatureSensorFactory implements ManagedServiceFactory { public void updated(String pid, Dictionary properties) throws ConfigurationException { // get configuration properties and copy to registration properties String address = properties.get(LOCATION_ADDRESS); String name = properties.get(LOCATION_NAME); Dictionary<String, String> registrationProperties = new Hashtable<String, String>(); registrationProperties.put( LOCATION_NAME, name); registrationProperties.put( LOCATION_ADDRESS, address); // create new transformer TemperatureSensorTransformer transformer = new TemperatureSensorTransformer(); // register newly configured transformer ServiceRegistration registration = bundleContext.registerService( XbeeAnalogDataTransformer.class.getName(), transformer, registrationProperties); } }

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public class BundleActivator implements BundleActivator { // factory PID - will be used as base PID for configured instances public static String PID = "com.pigglogic.phomenet.xbee.sensor.temperature"; public void start(BundleContext context) throws Exception { // create ManagedServiceFactory instance sensorFactory = new XbeeTemperatureSensorFactory(context); Dictionary properties = new Hashtable<String, String>(); // set SERVICE_PID property to our factory PID properties.put(Constants.SERVICE_PID, PID); // register factory instance factoryRegistration = context.registerService( ManagedServiceFactory.class.getName(), sensorFactory, properties); }

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What is allowed in configuration?

  • What are the attribute names?
  • What type of data do they take?
  • Are they required?

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Metatype Specification

  • Specify attributes used in configuration
  • name, type, required, default value, etc.
  • XML file in OSGI-INF/metatype
  • Felix web console will use this data to

dynamically create a configuration UI

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<metatype:MetaData xmlns:metatype="http://www.osgi.org/xmlns/metatype/v1.0.0"> <OCD description="xbee-temperature-sensor" name="com.pigglogic.phomenet.xbee.sensor.temperature" id="com.pigglogic.phomenet.xbee.sensor.temperature"> <AD name="Location Name" id="location.name" required="true" type="String" default="Temperature Sensor"/> <AD name="Location Address" id="location.address" required="true" type="String"/> <AD name="Correction" id="location.correction" required="false" type="Double" default="0.0"/> </OCD> <Designate pid="com.pigglogic.phomenet.xbee.sensor.temperature" factoryPid="com.pigglogic.phomenet.xbee.sensor.temperature"> <Object ocdref="com.pigglogic.phomenet.xbee.sensor.temperature"/> </Designate> </metatype:MetaData>

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Configure Sensor

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g! xsample $x1 Command returned with status OK Raw data in response:12013e Number of samples 1 Digital I/O No digital I/O data in response. Analog Data 1: 13E(318) Transformer reports value of -11.609971

Sample with Transfomer

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Collecting and Recording Data

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xbee-listener bundle

XbeeLib xbee- listener

XBeeService

Event Admin temp- sensor recorder

Observation Recorder Event Admin XbeeAnalogDataTransfomer

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Piping Hot Data

  • xbee-listener gets data from XBeeService,

but what to do with it?

  • Needs to find a transformer that will

handle the data

  • There should be a number of transformers

registered

  • Chooses based on source address

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Recording data

  • xbee-listener records transformed data
  • Finds an instance of

ObservationRecorder service

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Default Storage

phomenet service Derby Config Admin

Observation Recorder

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NoSql?

  • What if we wanted to be cool and store

data in Cassandra?

  • We could provide a different bundle that

implements ObservationRecorder

  • but uses Cassandra instead of Derby

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Visualizing Sensor Data

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Show me a GUI!

  • Web page GUI
  • Show latest observation for each sensor

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phomenet-web

phomenet- web Felix Web Console

Servlet

Event Admin

Event Handler

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Observation Events

  • xbee-listener posts an OSGi event when

data is transformed

  • Event topic is “phomenet/Observation/

Temperature/<address>”

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OSGi Event Admin

  • Bundles can post events
  • Bundles can register to be notified of

posted events

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Posting an Event

// build Map containing event data Map<String, Object> eventProperties = new HashMap<String, Object>(); eventProperties.put("location.name", locationName); final String addressString = frame.getSourceAddress().toString(); eventProperties.put("location.address", addressString); eventProperties.put("observedValue", value); // create Event with topic and properties final Event event = new Event( "phomenet/Observation/Temperature/" + addressString, eventProperties); // call postEvent with event eventAdmin.postEvent(event);

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Listening to Events

public void start(BundleContext context) throws Exception { Hashtable<String, Object> props = new Hashtable<String, Object>(); // Felix web console extension properties props.put("felix.webconsole.label", "phomenet"); props.put("felix.webconsole.title", "pHomeNet Console");

// property to say that we want all Observation events props.put(EventConstants.EVENT_TOPIC, "phomenet/Observation/*");

// register under Servlet and EventHandler interfaces webConsoleRegistration = context.registerService( new String[] {Servlet.class.getName(), EventHandler.class.getName()}, new PhomenetConsolePlugin(context), props); }

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Extending Web Console

  • Register a class that extends HTTPServlet
  • Add properties
  • felix.webconsole.label - used in URL
  • felix.webconsole.title - title of page

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Registering Extension

public void start(BundleContext context) throws Exception { Hashtable<String, Object> props = new Hashtable<String, Object>(); // Felix web console extension properties

props.put("felix.webconsole.label", "phomenet"); props.put("felix.webconsole.title", "pHomeNet Console"); // property to say that we want all Observation events props.put(EventConstants.EVENT_TOPIC, "phomenet/Observation/*");

// register under Servlet and EventHandler interfaces webConsoleRegistration = context.registerService( new String[] {Servlet.class.getName(), EventHandler.class.getName()}, new PhomenetConsolePlugin(context), props); }

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Resources

  • XBeeLib - kenai.com/projects/xbeelib
  • pHomeNet - kenai.com/projects/phomenet

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Resources

  • XBee 802.15.4 OEM module
  • http://www.digi.com/products/wireless/point-multipoint/xbee-series1-

module.jsp#overview

  • Droids XBee USB board
  • http://www.droids.it/990_002.html
  • MCP9700 Temperature Sensor
  • http://www.microchip.com/wwwproducts/Devices.aspx?

dDocName=en022289

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