ZigBee Based Wireless Sensor Networks

P06501

Introduction

Team Members EE: Jared Titus, Brandon Good, Nick

Yunker CE: Ryan Osial, Justin Thornton

Coordinator Dr. Reddy

Mentor Dr. Hu

Sponsors Sensorcon PCB Express

Needs Assessment Problem:

Crossbow Technology provides wireless sensor motes but cost deters the creation of large networks.

Budget: $1000 for parts, fabrication, and

assembly Solution:

Create low cost ZigBee Data Forwarding Unit (DFU) hardware and software prototype

ZigBee Standard

Low-power Low-cost Built on IEEE 802.15.4 standard Defines the protocols for creating

self-organizing mesh networks Three types of devices:

ZigBee Coordinator, Full-Function Device (FFD), and Reduced-Function Device (RFD)

ZigBee DFU Requirements Motes shall connect to sensors through

Interrupt and Analog-Digital Converter (ADC) connections

Motes shall be battery powered or USB powered. A RFD should be able to operate autonomously for three months

Motes shall be less than 9 sq. inches In volume production (>5000 units)

motes should cost less than $20 Motes shall form a bi-directional mesh

network.

ZigBee DFU Requirements Motes shall interface to a PC via USB Motes shall support adjustable

periodic data reporting, threshold reporting, and querying of data

A Graphical User Interface (GUI) shall allow the user to monitor and control the network

ZigBee DFU hardware shall support Coordinator, FFD, and RFD software.

Concept Design 3 Different Designs were considered Concept 1: Custom Hardware (Microcontroller and RF

Transceiver) with TinyOS networking stack Concept 2: Custom Hardware (Microcontroller and RF

Transceiver) with Custom ZigBee stack Concept 3: Custom Hardware (SoC) with a proprietary

ZigBee stack

Abstract Custom Hardware Designs

Atmega 128 Chipcon 2420

2.4

GH

z A

ntF

TD

I 232

Mote

UartLines

SPIInterface R

F S

igna

l

Ember250 - SOC

2.4

GH

z A

ntF

TD

I 232

Mote

UartLines R

F S

igna

l

Concept Pros and Cons

Concept 1 Concept 2 Concept 3

Pros -Low Cost-Open Development

-Low Cost-Open Development-More network control

-Vendor provided Stack-Less Hardware

Cons -No standardizing body-Not Zigbee Compliant-Complicated Layout

-Very Complicated Software-Complicated Layout

-Less network control-Untested SoC Solution-Cost of Stack

Feasibility Selected Viable Concepts to Analyze Created Pugh Matrix

Chose Evaluation Criteria based on: Requirements Time and cost to implement

Created Criteria Weighting Matrix Applied Weights to Each Criteria Selected Final Design based on Weighted

Pugh Ember – 100% Custom Stack – 87.1% Crossbow MicaZ and Software – 85.9% TinyOS + Berkley HW Design – 79.5%

Hardware

Power Switcher System on Chip (SoC) Antenna with Balun Impedance

Matching USB–UART Bridge Sensor Board

Power Switcher

Switches between USB 3.3V and battery 3V source when plugged into or disconnected from a computer

Enable signal provided by EM250 chip controls switching

TI Dual pair CMOS 4007 chip used in implementing this circuit.

M1

MbreakN

M2 MbreakN

M3MbreakN

M4

MbreakP

M5MbreakP

M6 MbreakP

USB 3.3V

MCU ENABLE

BATTERY 3V

0

C15pF

OUT

System on Chip (SoC)

Ember 250 System on Chip used. Integrates Microcontroller, 2.45GHz

ZigBee Transceiver, 128kB flash memory and 5kB SRAM into one compact 5mm x 5mm package.

Antenna with Balun Circuit

Antenna Factor 2.45GHz antenna. 6.5mm x 2.5mm SMT packaging allows for

compact MOTE design without a large whip antenna.

Balun circuit matches the 200Ω characteristic impedance of EM250 to 50Ω Antenna Impedance.

E 1A N TE N N A

C 65 p F

C 5

. 7 5 p F

C 7. 7 5 p F

1 2L 2

7 . 5 n H1

2

L 33 . 9 n H

1

2

L 47 . 5 n H

1 . 8 V

G N D

R F _ I N _ P

R F _ I N _ N

USB–UART Bridge

Allows for USB connection between PC and EM250 chip by use of a virtual communications port

FTDI communicates with EM250 using UART Provides power from USB when connected

Sensor Board

Integrates 2 Analog Devices temperature sensors and 1 light sensor.

Light sensor used to wake up MCU from sleep. Dual temp sensors used to show that multiple

analog sensors can be used on one MOTE.

Interfaces

USB/RS-232 Virtual Comm Port (VCP)

Universal Asynchronous Receiver-Transmitter (UART)

Serial Interface (SIF) Flash Programming and Real Time

Debugging of Ember EM250 Sensor Board Interface

8 pin interface between Sensor Board and Mote

3 pairs of Data/Enable, Vcc, and GND

Microcontroller SoftwareInitialize Stage

(Hardware/Serial Comm.)

Initialize Network Stack

Join Network

Configure Defaults

Sleep for X (sec)

Need to Transmit?

Send Data

Listen for Messages for X (sec)

Received New Data?

No

Update Config

Yes

Yes

No

Reduced Function Device(ZigBee End Device – ZED)

Microcontroller SoftwareInitialize Stage

(Hardware/Serial Comm.)

Initialize Network Stack

Join Network

Configure Defaults

Message Received?

Send Data

Update Config

Listen/Wait

Interrupt Occur?

Message for Me?

Yes

No

Need to Send Data?

Yes

No

Yes

No

Yes

No

Full Function Device(Zigbee Router – ZR)

Microcontroller SoftwareInitialize Stage

(Hardware/Serial Comm.)

Initialize Network Stack

Start Network

Configure Defaults

Listen/Wait

Message Received

Determine Desitination

Send Data to Host Computer

Send Data to Zigbee Device

Update Self/Network

Coordinator(Zigbee Coordinator – ZC)

Network Design Coordinator

Gatekeeper to network Routes Packets

Router Routes Packets Queues data for sleeping End Device

End Device Sleeps when inactive Queries parent for data

Network Design contd. Packet Routing

Ad-hoc On-demand Distance Vector (AODV)

Determines path though network inreal-time

Assumes that nodes may leave network at any time

Uses Link-Quality-Indicator (LQI) and number of hops as a selection metric

PC to Mote Messages Report Rate Polling Rate ADC Sampling Threshold

Boundary Query Node Data Get Routing

Table Reset Change Power

Profile

Command Message Layer

Command Header Layer

Source-Destination Layer

Serial Interface Layer

USB Interface Layer

Mote to PC Messages Coordinator

Routing Table Sensor Data

Data Layer

Data Header Layer

Source-Destination Layer

Serial Interface Layer

USB Interface Layer

GUI – Main Form Shows the Network Status Shows the Alerts in the Network Controls the other Network Views

Network Topology Mote Parameter Tree Mote Sensors

GUI – Network Topology Form

Displays all the mote in the network Shows all the communication paths

between the motes Mote placement on the form can be

rearranged. Sensor Data can be displayed for

motes

GUI – Mote Tree Form Displays the parameter values for

each mote in the network. Update parameter values for a

mote/motes

GUI – Mote Sensor Form Displays the sensor data for each mote

in the network.

Test Plan A test procedure was written for each

requirement of the project.

Example Test ProcedureRequirement 3.5Description: Motes shall have a minimum of 3

months autonomous operation on battery power supply

Test Plan:1. Place current probes between the battery and mote.2. Turn on the mote and allow it to perform normal

network operations3. Measure the average current draw.4. Divide the power of the battery (mAh) by the

average current draw to find the hours in which it can operate

Implementation Plan Week by week breakdown of what will be accomplished in SDII

Week 1: Star Networking on Dev boards Multihop on Dev boards

Week 2: Initial GUI milestone 1 (partial implementation) Initial firmware to Motes

Week 3: GUI milestone 2 (less network topology displayed) Star Networking on Motes Multihop on Motes Basic Mesh networking on Dev Boards

Week 4: Basic Power Management implemented (mote operation only) Basic Mesh Networking on Motes

Week 5: GUI completed

Week 6: Full Mesh Networking on ZigBee DFU completed

Week 7: Power management implemented (fully for mote)

Week 8: Testing and documentation

Week 9/10: Design/Project Completed IEEE regional Senior Design Competition

Bill of Materials Budget

$1000 from Sensorcon Ember Development Kit - $2500

Donation from Mark Wagner (Sensoncon)

Total Cost for 10 Motes - $176.07 Total Cost for Additional Items -

$360.01 Total Project Cost - $536.08 Each mote costs ~$21 to build

(with EM250)

ZigBee DFU

Questions ?