Building Wireless Sensor Networks

with ZigBee, XBee, Arduino, and Processing

by Robert Faludi • 2010 • 318 pages

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Technology Programming Reference

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Key Takeaways

1. ZigBee: The Wireless Protocol for Low-Power, Mesh Networking

"ZigBee is a standard communications protocol for low-power, wireless mesh networking."

ZigBee's unique features make it ideal for sensor networks and home automation:

Low power consumption
Self-healing mesh networking
Support for up to 65,000 nodes
250 kbps data rate at 2.4 GHz

ZigBee is built on the IEEE 802.15.4 standard and adds routing and networking capabilities. It's designed for applications that require long battery life and secure networking, but don't need high bandwidth. Examples include:

Smart energy systems
Home automation
Industrial control
Healthcare monitoring

2. XBee Radios: Configurable Modules for ZigBee Communication

"XBee is a brand of radio that supports a variety of communication protocols, including ZigBee, 802.15.4, and WiFi, among others."

XBee modules offer flexibility and ease of use for ZigBee implementations:

Multiple form factors (through-hole, surface mount)
Various antenna options (chip, wire, U.FL connector, RPSMA connector)
Configurable as Coordinator, Router, or End Device

XBee radios can be configured using:

AT commands for simple setups
API mode for more complex operations
X-CTU software for firmware updates and configuration

These modules integrate easily with microcontrollers like Arduino, making them popular for prototyping and small-scale deployments.

3. Network Topologies: Pair, Star, Mesh, and Cluster Tree

"ZigBee networks can connect together in several different layouts or topologies to give the network its structure."

ZigBee supports multiple topologies to suit various application needs:

Pair: Simplest form, just two nodes
Star: Central coordinator with multiple end devices
Mesh: Routers relay messages, extending network range
Cluster Tree: Combination of star and mesh topologies

Each topology has its advantages:

Star is simple but limited in range
Mesh offers redundancy and self-healing
Cluster Tree balances complexity and coverage

The choice of topology depends on factors like physical layout, power requirements, and desired network resilience.

4. Addressing in ZigBee: 64-bit, 16-bit, and Node Identifiers

"Almost every person has an address where he can be reached, usually one that is unique to him. Many people have more than one. We have mailing addresses, email addresses, phone numbers, passport numbers, and the list goes on. Each kind of address or identifier serves a slightly different purpose. It's the same with radios."

ZigBee uses multiple addressing schemes for flexibility and efficiency:

64-bit address: Unique, factory-assigned "serial number"
16-bit address: Network-assigned for efficient routing
Node Identifier: Human-readable string for easy identification

Addressing types and their uses:

64-bit: Guaranteed unique across all ZigBee devices
16-bit: Dynamically assigned, unique within a network
Node Identifier: Optional, user-assigned name

Understanding these addressing methods is crucial for configuring devices and troubleshooting network issues.

5. AT Commands: Configuring XBee Radios for Communication

"Every AT command starts with the letters "AT," which stands for "attention." The idea is to get the attention of the device, in this case our XBee radio."

AT commands provide a simple interface for configuring XBee radios:

Enter command mode with "+++"
Use commands like ATID (PAN ID), ATDH/ATDL (destination address)
Write settings to non-volatile memory with ATWR

Common AT commands:

ATID: Set/read PAN ID
ATMY: Read 16-bit network address
ATDH/ATDL: Set/read destination address
ATNI: Set/read Node Identifier

AT mode is suitable for simple configurations and direct human interaction with the radio.

6. API Mode: Advanced Control and Data Handling

"APIs let one computer application request services from another application in a standard manner."

API mode offers structured data exchange for more complex applications:

Allows simultaneous communication with multiple destinations
Provides delivery confirmation and remote configuration
Enables advanced features like firmware updates and network management

API frame structure:

Start delimiter (0x7E)
Length bytes
Frame-specific data
Checksum

API mode is essential for:

Receiving I/O samples from remote devices
Managing large networks
Integrating XBee radios with computer systems

7. Creating Sensor Networks: From Simple to Complex

"Building Wireless Sensor Networks is an essential guide for anyone interested in wireless communications for sensor networks, home networking, or device hacking."

Sensor networks can be built incrementally , starting with simple projects:

Basic paired communication (e.g., wireless doorbell)
Multi-node temperature sensing network
Home automation systems

Key components for sensor networks:

XBee radios for wireless communication
Sensors (temperature, light, motion, etc.)
Microcontrollers (e.g., Arduino) for local processing
Power sources (batteries, solar panels)

As networks grow, consider:

Scalability of addressing and routing
Power management for battery-operated nodes
Data aggregation and visualization techniques

8. Sleep Mode: Extending Battery Life in ZigBee Networks

"Going wireless often means cutting the electric cord. Projects that are mobile or remotely located frequently use batteries or another constrained power source that demands economizing on energy."

Sleep mode dramatically extends battery life in ZigBee networks:

Cyclic sleep: Radio wakes periodically to check for messages
Pin sleep: External signal controls sleep state

Sleep mode configuration:

ATSM command sets sleep mode
ATSP sets sleep period
ATST sets time before sleep

Considerations for sleep mode:

Parent devices must buffer messages for sleeping children
Trade-off between power savings and responsiveness
Some nodes (e.g., routers) typically cannot use sleep mode

9. Internet Connectivity: Gateways and the XBee Internet Gateway (XIG)

"The XBee Internet Gateway is a Python program that can be loaded onto any ConnectPort right out of the box. It's an interface that mirrors the interactions humans have in web browsers."

Gateways bridge ZigBee networks to the Internet , enabling:

Remote monitoring and control
Data aggregation and cloud storage
Integration with web services

XBee Internet Gateway (XIG) features:

Runs on ConnectPort devices
Translates between ZigBee and HTTP protocols
Allows XBee networks to interact with web services

Setting up an Internet-connected ZigBee network:

Configure a ConnectPort with XIG
Set up XBee radios to communicate with the gateway
Use simple URL-like commands to interact with web services

10. Data Sharing and Visualization: Bringing Sensor Data to Life

"By putting your data someplace accessible, you'll be able to strut your stuff, share with colleagues, and possibly pipe your information into other projects all over the world."

Sharing sensor data enhances its value through:

Collaboration with other researchers or enthusiasts
Integration with data visualization tools
Contribution to larger data sets or citizen science projects

Popular platforms for sharing sensor data:

Pachube (now Xively): Cloud-based service for real-time data
ThingSpeak: Open-source platform for IoT applications
Custom web applications using frameworks like Processing

Visualization techniques:

Real-time graphs and charts
Geographic mapping of sensor locations
Interactive dashboards for data exploration

By sharing and visualizing data, sensor networks can provide insights and value beyond their immediate application, contributing to a broader understanding of our environment and the Internet of Things ecosystem.

Last updated: May 6, 2025

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FAQ

What is Building Wireless Sensor Networks by Robert Faludi about?

Comprehensive hands-on guide: The book is a practical manual for building wireless sensor networks using ZigBee, XBee radios, Arduino, and Processing, suitable for both beginners and experienced makers.
Step-by-step project focus: It walks readers through real-world projects, from simple wireless doorbells to mesh networks and Internet-connected devices, emphasizing learning by doing.
Emphasis on ZigBee protocol: The book explains why ZigBee is ideal for sensor networks, highlighting its mesh networking, power-saving, and security features.
No prior expertise required: Written for hobbyists, students, designers, and artists, it assumes no engineering or computer science background.

Why should I read Building Wireless Sensor Networks by Robert Faludi?

Expert, accessible instruction: Robert Faludi is a recognized expert in wireless sensor networks, offering clear, authoritative, and practical advice throughout the book.
Beginner-friendly approach: The book is designed for readers without technical backgrounds, providing foundational knowledge and gradually introducing more complex topics.
Broad applicability: Whether your goal is home automation, interactive art, or large-scale sensor networks, the book equips you with the skills and tools to succeed.
Future-proof learning: It introduces advanced ZigBee features and trends, preparing readers for ongoing developments in wireless networking.

What are the key takeaways from Building Wireless Sensor Networks by Robert Faludi?

Hands-on learning is essential: The book emphasizes building and experimenting with real projects to gain practical skills in wireless networking.
Understanding ZigBee mesh networking: Readers learn the structure, advantages, and configuration of ZigBee mesh networks, including device roles and routing.
Power management matters: The book covers sleep modes and energy-saving techniques crucial for battery-powered sensor nodes.
Integration with the Internet: It demonstrates how to connect sensor networks to the web, enabling remote monitoring and data sharing.

What are the main components and tools recommended in Building Wireless Sensor Networks for beginners?

XBee Series 2 ZigBee radios: The book recommends Digi’s XBee Series 2 radios for their mesh networking capabilities and beginner-friendly setup.
Adapters and breakout boards: Essential hardware includes USB adapters like the SparkFun XBee Explorer and breadboard-compatible breakout boards for easy prototyping.
Software tools: Digi’s X-CTU (for Windows) is used for firmware updates and configuration, while terminal programs like CoolTerm and Tera Term facilitate communication.
Arduino and Processing: Arduino boards add local logic and I/O, while Processing is used for visualizing sensor data on a computer.

How does Building Wireless Sensor Networks by Robert Faludi explain the ZigBee protocol and its network structure?

Layered protocol overview: ZigBee builds on IEEE 802.15.4, adding mesh networking, routing, and self-healing capabilities.
Device roles: Every ZigBee network includes a coordinator (network manager), routers (message relays), and end devices (sensors/actuators that don’t relay messages).
Network topologies: The book covers pair, star, mesh, and cluster tree topologies, with mesh networks offering the most flexibility and robustness.
Protocol stack details: Advanced sections explain the PHY, MAC, Network, APS, and ZDO layers, as well as application profiles and clusters.

What is the difference between XBee Series 1 and Series 2 radios according to Robert Faludi?

Hardware and protocol: Series 1 uses a Freescale chipset and supports simple 802.15.4 networks, while Series 2 uses an Ember chipset and supports full ZigBee mesh networking.
Interoperability: Series 1 and Series 2 radios are not compatible; networks must use only one series.
Feature comparison: Series 2 radios offer better range, lower power consumption, and more digital I/O pins, but lack analog or PWM outputs.
Use case guidance: Series 1 is for simple, small systems; Series 2 is essential for robust, scalable sensor networks and is the book’s focus.

How does Building Wireless Sensor Networks by Robert Faludi guide readers in configuring and using XBee radios?

Firmware roles and modes: The book explains how to load coordinator, router, or end device firmware and operate radios in AT (transparent) or API mode.
AT command configuration: Readers learn to enter command mode, use AT commands to set parameters like PAN ID and I/O pin modes, and save configurations.
Serial terminal usage: Step-by-step instructions are provided for using terminal programs to communicate with and configure XBee radios.
Practical troubleshooting: The book offers tips for common setup issues and best practices for reliable communication.

What is API mode in XBee radios, and why does Robert Faludi recommend it?

Structured communication: API mode sends and receives data in well-defined frames, enabling robust and unambiguous communication.
Advanced features: It allows dynamic addressing, error checking, transmission status reports, and remote configuration.
Essential for scalability: API mode is crucial for building scalable sensor networks and advanced applications requiring reliability and control.
Frame parsing: The book explains how to interpret different API frame types, such as AT commands, transmit requests, and I/O data samples.

How does Building Wireless Sensor Networks by Robert Faludi address sensor input and output with XBee radios?

Direct I/O capabilities: XBee Series 2 radios can handle digital and analog inputs and digital outputs without an external microcontroller for simple tasks.
Limitations: The radios have limited I/O pins, no analog output, and no local logic, so complex processing requires an Arduino or similar microcontroller.
Configuration details: The book provides AT commands for setting pin modes, sample rates, and pull-up resistors, and explains how to interpret I/O data in API mode.
Project integration: Readers learn to combine XBee I/O with Arduino for more advanced sensing and actuation.

What practical projects does Building Wireless Sensor Networks by Robert Faludi include, and what do they teach?

Wireless doorbell: Teaches basic wireless communication, input/output handling, and Arduino programming.
Romantic lighting sensor: Demonstrates sensor data collection, wireless transmission, and feedback using a photoresistor and LED indicator.
Simple sensor network: Guides readers through building a mesh network of temperature sensors with real-time data visualization in Processing.
Direct actuation and Internet projects: Includes controlling appliances via relays and creating Internet-connected applications like a Twitter Reader.

How does Building Wireless Sensor Networks by Robert Faludi explain power management and sleep modes in ZigBee networks?

Importance of power saving: The book emphasizes sleep modes for extending battery life in sensor nodes, sometimes from hours to years.
Sleep mode types: It details four main sleep modes for XBee end devices, balancing power savings with wake-up latency and control complexity.
AT command configuration: Six key AT commands (SM, SN, SP, ST, SO, WH) are explained for setting sleep behavior and timing.
Practical trade-offs: The book discusses message buffering, parent device requirements, and limitations of sleeping end devices.

How does Building Wireless Sensor Networks by Robert Faludi guide readers in connecting ZigBee sensor networks to the Internet?

Gateway concepts: The book explains how gateways bridge ZigBee networks to the Internet, using devices like Digi ConnectPort or embedded modules.
XBee Internet Gateway (XIG): XIG is a Python program that allows ZigBee radios to send URLs and receive web content, simplifying Internet access for sensor networks.
Step-by-step setup: Readers are guided through installing and configuring XIG, testing connectivity, and integrating with web services.
Data sharing platforms: The book introduces Pachube (now Xively) for uploading, storing, and sharing sensor data online, with example code for integration.