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Building Tomorrow’s Internet of Things:

Latest Standardization Trends and

Hands‐on Programming Tutorial

Dr. Thomas Watteyne Berkeley Sensor and Actuator Center

University of California, Berkeley

WCNC 2010, Sydney

18 April 2010

Building Tomorrow’s Internet of Things: Latest Standardization Trends andHands-on Programming Tutorial

Dr. Thomas WatteyneBerkeley Sensor and Actuator Center


WCNC, 18 April 2010

2

Outlook

1. Introduction to Sensor Networks

2. Industrial Developments

3. Towards A Standards-Based Stack

4. IoT in Practice

5. Programming Tour

3

Acknowledgments

• Some slides and the contents of some slides have been either entirely or partially reproduced with thanks from:

– Mischa Dohler, CTTC, Spain

– Kris Pister, UC Berkeley, USA

– Abdelmalik Bachir, Imperial College, UK

– Zach Shelby, Sensinode, Finland

– IETF ROLL presentations

– companies’ websites

• Thanks to Texas Instruments for providing the eZ430-RF2500 kits– Cathy Wicks

– Robert Owen

– Jacob Borgeson

4

Installation Required! [1/5]

Step 0: Requirements

• A laptop running Windows (XP preferred)

• An eZ430-RF2500 kit

5


Step 1: eZ430-RF2500 Sensor Monitor Demo

While we will never run the Sensor Monitor (a graphical interface to the Texas Instruments Sensor Monitor Demo), installing this is the quickest way of installing the driver for Windows to understand the eZ430-RF2500 connected to your computer.

• Download the eZ430-RF2500 Sensor Monitor Demo from http://www.ti.com/ (currently revision C, 3MB)

• Unzip that file and run Sensor Monitor Installer.exe

• Use default configurations during installation

• Do not keep the Sensor Monitor program running after the install, as it will interfere with the other tools we will be using

6


Step 2: IAR Kickstart for MSP430

IAR is the tool used to program the eZ430-RF2500 boards. Kickstart is the free edition, which can compile binary code up to 4kB in size. For larger sizes (not used in this tutorial), you need to buy the full version of IAR.

• Download the latest IAR Embedded Workbench kickstart edition for MSP430 from http://www.iar.com/ (currently version 4.21, 106MB)

• Use the default configuration settings during installation

7


Step 3: PuTTY

PuTTY is used to read from the serial COM port created when the eZ430-RF2500 board is connected to the host computer.

• Download http://the.earth.li/sgtatham/putty/latest/x86/putty.exe (currently release 0.60, 444kB)

• There is no installation needed, double-clicking should start the application

8


Step 4: Python and PySerial

We will use Python scripts to interface our laptops with the eZ430-RF2500.

• Download and install Python from http://www.python.org/, versions 2.5.4 and 2.6.4 are known to work

• Download and install PySerial (which allows Python to connect to a serial, or COM, port) from http://pyserial.sourceforge.net/,pyserial-2.5-rc1.win32.exe is known to work

1

Thomas Watteyne @ WCNC 2010

1. Introduction to Sensor Networks

2

Section 1 - Overview

1. Introduction to Sensor Networks1.1 From Smart Dust to Smart Plants

1.2 Applications

1.3 The Nature of Wireless

1.4 Conclusions


3


1.1 From Smart Dust to Smart Plants

4

The Promise of Wireless

time

$

sensing

computation

communication


5


time

size

power

cost


6

1997, the Smart Dust vision


7

1999, Optical Communication


8

Off-the-Shelf Hardware


9

2001, Intel Developers Forum

• 800 motes

• 8-level dynamic network


10

2001, 29 Palms Demo


11

S. Oh et al, "Tracking and coordination of multiple agents using sensor networks: system design, algorithms and experiments," Proc. of the IEEE, 2007.S. Kim et al, “Health Monitoring of Civil Infrastructures Using Wireless Sensor Networks,” IPSN, Cambridge, MA, April 2007A. Ledezci, http://www.isis.vanderbilt.edu/projects/countersniperJ. Lees et al, “Reventador Volcano 2005: Eruptive Activity Inferred from Seismo-Acoustic Observation”, Jnl, of of Volcanology and Geothermal Research, 2007

Wireless Sensor Networks

Sensor Networks for SecurityStructural Monitoring

Sniper Localization

Environmental Monitoring


12


1.2 Applications

13

We all agree…


14

Building Monitoring

• UC Berkeley’s Center for Built Environment

• Seismic testing demo: real-time data acquisition

• hundreds of sensors on 3 floors

• wiring cost by far outweighs sensor cost.

• $200 vs. $5,000 per node in a wireless version.

• A few days installation(vs. weeks)Thomas Watteyne @ WCNC 2010

15

Habitat Monitoring

• Overview– Study the Leach's Storm Petrel's Habitat

– UC Berkeley, Prof. Dave Culler

– Deployed during summer 2002 for 4 months on an uninhabited island 15km off the coast of Maine, USA

• Platform– 43 mica motes

– TinyOS

– Humidity, pressure, temperature, light, IR radiation

• Networking– Transmit-only nodes

– One transmission every 70 seconds

– 1.7% duty cycle

– Simple CSMA MAC


16

Precision Agriculture• Overview

– Micro-climate study in a potato field

– Delft U. Technology, Prof. Langendoen

– Deployed during Summer 2005 for 3 months in a potato field in Holland

• Platform– 100 motes (AtMega128L, CC1000)

– TinyOS

– Humidity, temperature

• Networking– T-MAC

– Single-hop (Mint routing)

– 11% duty cycle


17

Automated Meter Reading• Overview

– Urban-wide Water Meter Reading

– Coronis Systems, Elster group

– Deployed since 2005 in Sable-d'Olonne, France

• Platform– 25,000 proprietary nodes

• Networking– Static routing tree

– Parent association done at deployment

– 10+ years (<.1% duty cycle)


18

Building Automation

Smart Grid Applications

IndustrialAutomation

Industrial Applications


19


1.3 The Nature of Wireless

20

Costs in Wireless Sensor Networks

Operation Time PowerEnergy

RequiredTechnology

Fill a packet with analog samples

1 s 0.025 mW 25 µJMSP430 @ 4 MHz,

80 Samples

Transmit or Receive a packet

0.006 s 50 mW 400 µJ CC2420

2.5 mJ to generate and pass this packet along100x more than to build it


21

Reliability

Reliability is challenged by:• external interference• multi-path fading


22

External Interference


23

First Challenge: External Interference

IEEE802.11(Wi-Fi)IEEE802.15.1(Bluetooth)IEEE802.15.4(ZigBee)


24

Typical Tx power

• IEEE802.11-2007: 100mW

• IEEE802.15.4-2006: 1mW


2.4 GHz

Channels 11-26

2.4835 GHz

5 MHz

2.4 GHz PHY


25

IEEE802.11b/g/nIEEE802.11a/n


868 MHz

433 MHz

2.4 GHz 5 GHz

IEEE802.15.4


26


• 45 motes*

• 50x50m office environment

• 12 million packets exchanged, equaly over all 16 channels

*data collected by Jorge Ortiz and David Culler, UCBPublicly available at wsn.eecs.berkeley.edu


27

Second Challenge: Multipath Fading


28


• Separate sender and receiver by 100cm

• Have sender send bursts of 1000 packets

• Have receiver count the number of received packets

• Move transmitter around in a 20cmx35cm square and start over


29


ch.11Thomas Watteyne @ WCNC 2010

30


ch.11 ch.12

0% reliability 100% reliability


31


ch.11

ch.13

ch.15

ch.17

ch.12

ch.14

ch.16

ch.18

ch.19

ch.21

ch.23

ch.25

ch.20

ch.22

ch.24

ch.26

changing channel improves performance


32

Taking A Real-World Example

• Doherty, Lindsay, Simon. “Channel-Specific Wireless Sensor Network Path Data”, ICCCN 2007.

• 44 nodes, 26 days


36

Pathloss

0 50 100 150 200 250 300-100

-90

-80

-70

-60

-50

-40

-30

-20

distance in feet

RS

SI (

dBm

) RSSI does not give an indication

about distance


37

Stability over all paths, all channels


38

2.405 GHz

2.480 GHz

802.

15.4

Cha

nnel

s

802.

11bg

Cha

nnel

s

* each dot represents 15 minutes



39



40



41


1.4 Conclusions

42

Conclusions

• Research– many network degrees of freedom, hence a lot of work

– focus is on intra wireless sensor network communication

– impact era has passed but numerous problems are still open

• Development– keep it simple and tailor to required application

– focus is on communication between WSN and Internet

– impact era is yet to come

• Business– WSN promise significant financial cost savings

– business takes off slower than anticipated due to various reasons


1


2. Industrial Developments

2


2. Industrial Developments2.1 The Promise of Wireless

2.2 Standardization Bodies

2.3 Startups

2.4 Conclusions


3


2.1 The Promise of Wireless

4



90%?

time

$

sensors

computation &communication

installation, connection,

commissioning

wired cost

reduced wiring cost

traditional wireless

wireless mesh

networking

5

Barriers to Adoption


* source: OnWorld, 2005

Reliability

Standards

Ease of use

Power consumption

Development cycles

Node size

0% 20% 20% 60% 80% 100%

6

Interoperability Issues


The Internet

7


2.2 Standardization Bodies

8

What are Standards?

• Normative standardization documents are– elaborated by a community

– publicly available without any discriminatory conditions

– published by Standards Developing Organizations (SDOs)

• SDO (Standards Developing Organization):– publish standards which

– rely upon national or international regulations

• Further facts about standards:– pushed for by consortia or forums

– popularity is reflected by the market

– serve as references for compliance purposes


9

Benefit of Standards

• Service Providers benefit because– they can design, develop and operate a wide range of services

– whatever the underlying but standard-compliant, heterogeneous technologies

• Vendors benefit because – they can access markets more easily with standard-compliant products

– proprietary technologies are restricted to niche markets (at best)

– at the risk of blurring competitive differentiation

• Customers benefit because – they can access a wide range of services

– without the burden of being tied to a given service provider or technology


10

Corporate View

• Standardization as a profitable business:– defend business stakes

– promote patents through the enforcement of a consistent IPR policy

• Standardization as a decision-making tool:– privileged space for consolidating and developing leadership positions

• Speed up the introduction of new products and/or services:– facilitated by a set of available standards

• Slow down the standardization process:– to extend the lifetime of an already-introduced yet proprietary product or service


11

Regulatory View

• Technology space is very complex:– stringent regulations are hence needed

– to facilitate control and possible billing (e.g. UMTS spectrum license)

• Standards serve as the technical references for regulation rules:– European directives and derived domestic laws

– part of the legal resolution of conflicts between competitors

– and/or customers and service providers

• Part of the corporate strategy:– corporate solutions evolve in a regulated manner

– mainly if regulators see a (financial) opportunity


12

Standardization Bodies

• Standards Developing Organization bodies can be – international (e.g. ITU-T, ISO, IEEE),

– regional (e.g. ANSI, ETSI), or

– national (e.g. CCSA)

• Standardization efforts pertinent to WSNs are:– IEEE (link and physical layer solutions)

– ETSI (complete M2M solutions)

– ISA (regulation for control systems)

– IETF (routing and network solutions)


13

IEEE – Overview

• Institute of Electrical and Electronics Engineers:– is one of the leading standards-making organizations in the world

– Standardization through IEEE Standards Association (IEEE-SA)

• IEEE standards affect a wide range of industries: – power and energy

– biomedical and healthcare

– information technology

– telecommunications

– transportation

– nanotechnology, etc.

• IEEE has close to 900 active standards, with 500 standards under development.


14

IEEE – The 802 “soup”• 802.1 High Level Interface (HILI) Working Group

• 802.3 CSMA/CD (Ethernet) Working Group

• 802.11 Wireless LAN (WLAN) Working Group

• 802.15 Wireless Personal Area Network (WPAN) Working Group– TG1 – WPAN, Bluetooth

– TG3c - mmWave

– TG4c - WPAN Alternative PHY for China

– TG4d - WPAN Alternative PHY for Japan

– TG4e - WPAN Enhancements

– TG4f - RFID

– TG4g - Smart Utility Neighborhood

– TG5 - WPAN Mesh Networking

– TG6 - Body Area Networks

– TG7 - Visible Light Communication

– IGthz - Interest Group Terahertz

– WNG - Standing Committee Wireless Next Generation

• 802.16 Broadband Wireless Acces s (BWA) Working Group

• 802.17 Resilient Packet Ring (RPR) Working Group

• 802.18 Radio Regulatory Technical Advisory Group

• 802.19 Coexistence Technical Advisory Group

• 802.20 Mobile Broadband Wireless Acces s Working Group

• 802.21 Media Independent Handover Working Group

• 802.22 Wireless Regional Area Networks Working GroupThomas Watteyne @ WCNC 2010

15

IEEE – WSN Related Standards

• The IEEE usually standardizes:– PHY layer of the transmitter

– MAC protocol rules

• The following IEEE standards are applicable to WSNs:– IEEE 802.15.4 (technology used by ZigBee and IETF 6LowPan)

– IEEE 802.15.1 (technology used by Bluetooth/WiBree)

– IEEE 802.11x (technology used by WiFi)

• Some facts and comments:– IEEE 802.15.4 has been the obvious choice but will get

– serious competition from ultra-low power (ULP) IEEE 802.15.1 (WiBree)

– low power IEEE 802.11 solutions are emerging (e.g. Marvell)


16

IETF – Overview

• Internet Engineering Task Force:– formed in 1986

– not approved by the US government

– composed of individuals, not companies

– quoting the spirit: “We reject kings, presidents and voting. We believe in rough consensus and running code.” D. Clark, 1992

• Quick overview on the IETF:– meets 3 times a year, and gathers an average of 1,300 individuals

– more than 120 active working groups organized into 8 areas

– IETF management (including area directors) is chosen by the community


17

IETF – Overview

• General scope of IETF:– above the wire/link and below the application

– TCP/IP protocol suite: IP, TCP, routing protocols, etc.

• However, layers are getting fuzzy:– MAC & application layers influence routing in WSN

– hence a constant exploration of "edges"

• Some curiosities:– there is no formal recognition for IETF standards by governments or SDOs

– IETF publications are very interesting for SDOs because of quick implementation


18

IETF – WSN Related Standards

• IETF 6LoWPAN [2005]– add IPv6 capabilities to wireless sensors

– end-to-end connectivity to/from the Internet

• IETF ROLL [2007]– identify application domains

– define a routing protocol for Wireless Sensor Networks

• IETF 6LoWApp [2009]– what goes on top of IP?

– brand new…


19


2.3 Startups

20

Dust Networks [US]

• Dust Networks facts:– founded in 2002 by industry pioneer Prof. Kris Pister, Berkeley, USA

– vision of a world of ubiquitous sensing – a world of connected sensors scattered around like specs of dust, or smart dust, gathering information economically and reliably, that had previously been impractical or impossible to acquire

– inventors of TSMP which are used in ISA100, Wireless HART and IEEE 802.15.4E

– emphasis on industrial control


21

Arch Rock [US]

• Arch Rock facts:– founded in May 2005 with a vision of providing a high quality, seamless integration of the

physical and virtual worlds that would enhance the information awareness of the individual and the enterprise

– company builds upon a decade of research at the University of California, Berkeley and Intel Research by David Culler et al.

– founder of a new operating system, TinyOS and Berkeley Mote, for small wirelessly connected computers that sense the physical environment and form vast embedded networks; emphasis on environmental monitoring & ind. control


22

Crossbow [US]

• Crossbow facts:– Global Leader in Sensory Systems; founded in 1995 by Mike Horton

– Products MEMS-Based Inertial Systems & Wireless Sensor Networking

– World-Wide Employee Base; Headquartered in San Jose, CA

– $25M in Venture Capital

– Cisco Systems, Intel Corporation, Morgenthaler Ventures, Paladin Capital

– emphasis on asset management & tracking


23

Coronis/Elster [FR, US]

• Coronis, France, (now bought by Elster, USA) in short:


24

Sensinode [FI]

• Sensinode facts:– leader in IP-based wireless sensor network (WSN) technology

– 1st on the market with a 6lowpan stack

– 6lowpan products and services: 6lowpan Devkits, Network Products, NanoStack 6lowpan Stack

– Engineering Services

– Sensinode is headquartered in Finland

– A 2005 spin-off of the University of Oulu, Finland based on a decade of research


25

etc.


Adurahttp://www.aduratech.com/

Berkeley Lighting control

Arch Rockhttp://www.archrock.com/

Berkeley

Elster Coronishttp://www.coronis.com/

Montpellier, France Automated Meter Reading

Crossbowhttp://www.xbow.com/

Berkeley

Dust Networkshttp://www.dustnetworks.com/

Berkeley Industrial Automation

Emberhttp://www.ember.com/

MIT

Federspiel Controlshttp://www.federspielcontrols.com/

Berkeley HVAC

Libeliumhttp://www.libelium.com/

Zaragoza, Spain

Maxforhttp://www.maxfor.co.kr/

Seongnam, South Korea

Millenial Nethttp://www.millennial.net/

MIT Smart Energy

Sensicast Systemshttp://www.sensicast.com/

Pinpoint

Sensinodehttp://www.sensinode.com/

Oulu, Finland

Sensys Networkshttp://www.sensysnetworks.com/

Berkeley Traffic light sensor

Sentilla (was MoteIV)http://www.sentilla.com/

Berkeley

Skywise Systemshttp://www.skywisesystems.com/

Beijing, China

Smartgrainshttp://www.smartgrains.com/

Paris, France Smart Parking

Streetline Networkshttp://www.streetlinenetworks.com/

Berkeley Smart Parking

26


2.4 Conclusions

27

Conclusions

• The Past– loads of proprietary wireless solutions have been mushrooming over past decade

– no or little inter-operability between these solutions

– danger of de-fragmented market is a reality

• The Present– proprietary solutions are still being developed and pushed for

– however, standardization is wrapping up at all layers of the stack

• The Future– integration of the to-be-finalized standards

– realization of Internet-of-Things


1


3. Towards A Standards-Based Stack

2

Application OpenADR, XML

Transport TCP, UDP

routingIETF RPL

IETF 6LoWPAN

MAC IEEE 802.15.4E

PHY IEEE 802.15.4-2006

Protocol Stack


IETF

IEE

E

3


3. Towards A Standards-Based Stack3.1 IEEE 802.15.4E

3.2 IETF 6LoWPAN

3.3 IETF RPL

3.4 OpenWSN

3.5 Conclusions


4


3.1 IEEE802.15.4E

5

15.4-2006, 15.4 PHY, 15.4 MAC, 15.4E?

• IEEE 802 LAN/MAN Standards Committee– standardizes a.o. 802.3 (Ethernet) 802.11

– http://www.ieee802.org/

• IEEE 802.15 Working Group for WPAN– wireless Personal Area Network

– standardizes a.o. 802.15.1 (Bluetooth), 802.15.4

– http://www.ieee802.org/15/

• IEEE 802.15 WPAN Task Group 4– low data rate solution with multi-month to multi-year battery life, very low complexity

– operating in an unlicensed, international frequency band

– sensors, interactive toys, smart badges, remote controls, and home automation, etc.

– first standard in 2003, updated in 2006

– standardizes both PHY and MAC

– http://www.ieee802.org/15/pub/TG4.html

• IEEE 802.15 WPAN Task Group 4e– define a MAC amendment to the existing standard 802.15.4-2006

– enhance and add functionality to the 802.15.4-2006 MAC to better support the industrial markets

– uses 802.15.4-2006 PHY

– draft standard on 03/08/2010, integrated in next revision of the 802.15.4 standard (exp. 2011)

– http://www.ieee802.org/15/pub/TG4e.html


http://www.ieee802.org/�

http://www.ieee802.org/15/�

http://www.ieee802.org/15/pub/TG4.html�

http://www.ieee802.org/15/pub/TG4e.html�

6

IEEE802.15.4 – Overview

• Emphasis of IEEE 802.15.4 is:– low-cost, low-speed ubiquitous communication between nearby devices with little to

no underlying infrastructure– basic framework assumes 10-meter communications area @ 250 kbit/s– lower transfer rates of 20, 40 and 100 kbit/s are now considered too– to meet embedded constraints, several PHY layers are available

• Key technology features are: – real-time suitability by reservation of guaranteed time slots– collision avoidance through CSMA/CA– integrated support for secure communications (128-bit AES encryption)– power management functions such as link quality and energy detection– 16 channels in ISM bands for operation, i.e. 868-868.8 MHz (Europe), 902-928 MHz

(North America), 2400-2483.5 MHz (worldwide)– star and mesh topologies can theoretically be built– support for low-latencies and dynamic device addressing


7

IEEE802.15.4 – PHY Layer

• The 2006 revision of the standard defines 4 PHY layers:– 868/915 MHz DSSS with binary phase shift keying (BPSK)

– 868/915 MHz DSSS with offset quadrature phase shift keying (OQPSK)

– 2450 MHz DSSS with offset quadrature phase shift keying (OQPSK)

– 868/915 MHz PSSS, i.e. combination of binary keying and amplitude shift keying

• The 2007 IEEE 802.15.4a version includes 2 PHY layers more:– Chirp Spread Spectrum (CSS) @ 2450 MHz ISM

– Direct Sequence Ultra-wideband (UWB) @ < 1GHz, 3-5GHz, 6-10 GHz

• Beyond these PHYs at the three bands, there are:– IEEE 802.15.4c for 314-316, 430-434 and 779-787MHz bands in China

– IEEE 802.15.4d for 950-956MHz band in Japan


8

IEEE802.15.4 – PHY Layer

• binary phase shift keying (BPSK)

• quadrature phase shift keying (QPSK)

• offset quadrature phase shift keying (OQPSK)


9

IEEE802.15.4 – 2.4GHz PHY

• O-QPSK, 250 kb/s, 62.5 ksymbol/s

• Direct Sequence Spread Spectrum

• Max PSDU = 127B

• Turnaround: TX-RX ≤ RX-TX ≤ 192us

• ED over 8 symbol periods

DSSS: 4 bits of information = 32 chips(raw data rate of 2Mbps)


10

IEEE802.15.4 – MAC Layer

• Some key attributes:– CSMA/CA channel access– manages access to the physical channel and network beaconing– controls frame validation, guarantees time slots, handles node associations– offers hook points for secure services

• In more details:– networks which are not using beaconing mechanisms utilize an un-slotted variation

which is based on the listening of the medium, leveraged by a random exponential backoff algorithm (acknowledgments do not adhere to this discipline)

– confirmation messages may be optional under certain circumstances, in which case a success assumption is made; timeout-based retransmission can be performed a number of times

– due to the maximization of battery life, the protocols tend to favor methods implementing periodic checks for pending messages, the intensity of which depends on application needs


11


• There are two general channel access methods:

• Non-Beacon Network:– simple, traditional multiple access system used in simple peer networks– standard CSMA conflict resolution– positive acknowledgement for successfully received packets

• Beacon-Enabled Network– can be used in beacon-request mode without superframes– superframe structure - network coordinator transmits beacons at predetermined

intervals– dedicated bandwidth and low latency– low power consumption mode for coordinator


12


• Super-Frame Structure for Beacon-Enabled Mode:


13

IEEE802.15.4 – Packet Format


4B of data(all 0’s) 0x7A

0-127

synchronization header physical header

MAC header

16-bit CRC

beacon, ACK, DATA, command

14

IEEE802.15.4 – Device Classes

• Full function device (FFD)– any topology

– network coordinator capable

– talks to any other device

• Reduced function device (RFD)– limited to star topology

– cannot become a network coordinator

– talks only to a network coordinator

– very simple implementation


15

Full function device

Reduced function device

Communications flow

Master/Slave

PANCoordinator

IEEE802.15.4 – Star Topology


16

Full function device Communications flow

Point to point Cluster tree

IEEE802.15.4 – P2P Topology


17

Full function device

Reduced function device

Communications flow

Clustered stars - for example,cluster nodes exist between roomsof a hotel and each room has a star network for control.

IEEE802.15.4 – Combined Topology


18

IEEE802.15.4 Scenario

• First node makes sure it is alone, scans for a “good” frequency and transmits beacons.

• New node scans (active or passive) and hears beacon. Sends an association request (indirect response). Tracks beacon periodically.

• Upstream data transmitted in CAP using CSMA/CA. If downstream data, coordinator set pending data field.

• Device can ask to (dis)allocate a GTS to the coordinator. GTS slots are announced in beacon, CSMA is not used in GTS slot.

• Secondary coordinators to create a generalized star topology.


19

IEEE802.15.4 - Problems

• Powered Routers– router nodes have their radio on all the time

– if battery-powered: 2400mAh AA pack @ 81mA (CC2420) -> 29h of lifetime

– assumption: mains powered

• Single channel operation– WiFi-like: one channel for the whole network– suffers from external interference (WiFi, Bluetooth)– suffers from persistent multipath fading (especially indoors)

• Topologies– works great in star topologies

– e.g. multiple switches connected to a single lamp

– extended star topologies are hard to manage


20

A

B

C

D

IEEE802.14.4E - TSCH

• Time Synchronized Channel Hopping

• cut time into slots

• have nodes follow a common schedule


21

IEEE802.14.4E - TSCH

• The channel offset is translated to frequency using a translation function

• This insures that successive packets sent over a same link are sent over all frequencies– iff the superframe length and

number if frequencies are mutually prime

frequency = (absolute slot number + channel offset)%16

superframe ASN channel offset frequency

1 8 1 9

2 18 1 3

3 28 1 12

4 38 1 6


22

IEEE802.14.4e - TSCH

A B


23


24


SETTING_CHANNEL

STARTING STARTED TXDATA RXACK STOPPED

Startup_time+Guard_time_large

TsTxOffset

Watchdog_TXDATA

TsRxAckDelay

TsAckWaitTime

SETTING_CHANNEL

STARTINGSTARTED

RXDATA TXACK STOPPED

Startup_time

TsRxOffset

TsPacketWaitTime

TsTxAckDelay

Watchdog_TXACK

Watchdog_TXACK+Guard_time_small

1 2 4 5 6 10 11

1 2 7 8 9 10 11

WAIT_TXACK STOPPING

WAIT_RXACK

STOPPING

Guard_time_large Guard_time_small

Stopping_time

SLOT_TIME>TsRxOffset+TsPacketWaitTime+TsTxAckDelay+Watchdog_TXACK+Stopping_time

26

Improved Reliability


27

Improved Connectivity


28

Improved Throughput


29

Improved Energy Consumption

• 2ms maximum de-synchronization

• 20ppm relative drift

• Resynchronization every 100 seconds (10ms slots)

0.010% idle duty cycle

• 25mA when mote is active

• 2400mAh batteries(AA batteries)

lifetime of 109 years(>> shelf-life)


30

Improved Throughput


31

visible light sensor

IR light sensor

humidity sensor

antenna

CC2420radio

MSP430 microcontroller

1 2 3 4

IEEE 802.15.4e - TSCH

• TelosB mote

• TinyOS operating system

• 30ms time slots

• 19kB ROM / 3kB RAM

• 10kbps over 14 hops


32


33


3.2 IETF 6LoWPAN

34

IPv4 vs. IPv6

• Internet Protocol v4 (IPv4):– IPv4 (RFC 791) originates from 1981

– upper layer protocols responsible for end-to-end reliability

– works over almost any layer 2 network and with many routing protocols

– addressing is being pushed to extremes by Internet growth

• Internet Protocol v6 (IPv6):– IPv6 (RFC 2460) is the next generation of the Internet Protocol

– complete redesign on IP addressing: hierarchical 128-bit address with decoupled host identifier; stateless auto-configuration; etc

– simple routing and address management

– majority of traffic not yet IPv6 but most PC operating systems already have IPv6, governments are starting to require IPv6, most routers already have IPv6 support

– IPv6 transition is coming slowly but quietly


35

• IPv4 ...

... versus IPv6 addressing:

IPv4 vs. IPv6


36

IPv4 vs. IPv6M

onday, September 26, 2011


37

IP headers

IPv4 header [RFC791], 1981

IPv6 header [RFC791], 1998Thomas Watteyne @ WCNC 2010

38

IETF 6LoWPAN - Overview

• Key properties:– IP for very low power embedded devices

– IETF Standard for IPv6 over IEEE 802.15.4: RFC4944, to be obsolete by IPHC

– 80% compression of headers

– IPv6 40-byte header -> 2 bytes (best case)

– UDP 8-byte header -> 4 bytes

– end-to-end Internet integration

– fragmentation (1260 byte IPv6 frame -> 127 byte 802.15.4 frames)


39

Header Compaction

Not compacted

Well-known value

Value inferred from IEEE802.15.4 header


40

Internet Integration


41


3.3 IETF RPL

42

IETF ROLL - Overview

• Routing Over Low-Power and Lossy Networks (ROLL):– IETF information discussion started in 2008

– Finalizing “RPL: IPv6 Routing Protocol for Low power and Lossy Networks”

– website: http://tools.ietf.org/wg/roll

– list: http://www.ietf.org/mail-archive/web/roll/current/threads.html

• Since WSNs are application specific, 4 scenarios are dealt with:– building applications: draft-ietf-roll-building-routing-reqs

– home applications: draft-ietf-roll-home-routing-reqs

– industrial applications: RFC 5673

– urban applications: RFC 5548


43

IETF ROLL – RPL

• Adopted as a working document by IETF ROLL on August 3, 2009

• Close integration with IPv6/6LoWPAN– DAG Information Option (DIO)

– Destination Advertisement Option (DAO)

• Core operation:– build a Directed Acyclic Graph (DAG) onto the connectivity graph of the

network, directed toward a DAG root

– each node has at least one DAG parent; nodes send inward traffic to their DAG parent

– nodes announce their presence to the DAG root using Destination Advertisement

– Source routing is used for outward traffic


44

• Constraint Based Routing– finding the shortest path according to some metrics satisfying a set of

constraints

• Objective Code Point (OCP) included in DIO:– The set of metrics used within the DAG

e.g. Expected Transmission Count (ETX)

– The objective functions used to determine the least cost constrained paths in order to optimize the DAGe.g. minimize ETX

– The function used to compute DAG Depthe.g. DAG Depth is equivalent to ETX

– The functions used to construct derived metrics for propagation within a DIOe.g. additive

IETF ROLL – RPL


45

IETF ROLL – RPL


wsn

.eec

s.er

kele

y.ed

u

46

IETF ROLL – RPL


wsn

.eec

s.er

kele

y.ed

u

47

IETF ROLL – RPL


48


3.4 OpenWSN

49

Charter

The OpenWSN project serves as a repository for open-source implementations of protocol stacks based on Internet of Things standards, using a variety of hardware and software platforms.


50

Open Source

• http://openwsn.berkeley.edu/

• Source code repository: Subversion with public check out

• Documentation: wiki

• Project management: Timeline & Roadmap

• Bug reporting: ticketing system


http://openwsn.berkeley.edu/�

51

Hardware/Software Platforms

• Hardware:– TelosB (2004)

MSP430f1611 (16-bit, 8MHz, 10kB RAM, 48kB ROM)CC2420

– Jennic JN5140 (2009)32-bit, 32MHz, 128kB RAM, 128kB ROM15.4 radio with RF ToF engine

– Atmel RAVEN Stick (2009)AT90USB1287 (8-bit, 16MHz, 8kB RAM, 128kB ROM), AT86RF230

– GINA 2.0 (2009)

• Software:– TinyOS

– Contiki

– FreeRTOS

– uC-OS II/III

– no-OSThomas Watteyne @ WCNC 2010

52

//Slot Durationsenum {

Startup_time = 114, //32kHz ticks = 3.479ms Guard_time_large = 33, //32kHz ticks = 1.007msGuard_time_small = 16, //32kHz ticks = 0.488msWatchdog_TXDATA = 393, //32kHz ticks = 11.993msWatchdog_TXACK = 213, //32kHz ticks = 6.500msStopping_time = 17, //32kHz ticks = 0.519ms

TsRxOffset = Startup_time,TsTxOffset = Startup_time+Guard_time_large,TsPacketWaitTime = Watchdog_TXDATA+Guard_time_large TsRxAckDelay = 1, //go in reception mode immediatelyTsTxAckDelay = TsRxAckDelay+Guard_time_small,TsAckWaitTime = Watchdog_TXACK+Guard_time_small//SLOT_TIME >= TsRxOffset+TsPacketWaitTime+TsTxAckDelay+Watchdog_TXACK+Stopping_timeSLOT_TIME = 983, //ticks = 29.999ms

};

Slot Organization


53

Full Debugging Environment


54

Memory Usage

ROM RAM

48kB

30788 B

RPL 802.15.4E

2196

0 B

OS

8828

B

10kB

2920B 1352 B1568 B


55

Next Step

OpenADRserver

sensor.network.com

datacollection

actuation


56


3.5 Conclusions

57

Conclusions

• Lifting barriers to adoption– Robust wireless communication through channel hopping

– A fully standards-based solution

– Internet integration provides ease of use

– Aggressive duty cycling provides <1% duty cycle

– Being implemented on the low-end of today’s motes

• openwsn.berkeley.edu


The Internet

1


4. IoT in Practice

2


4. IoT in Practice4.1 Off-the-Shelf Hardware

4.2 Operating Systems

4.3 Development Environment

4.4 Tips & Tricks


3


4.1 Off-the-Shelf Hardware

4

Hardware - Overview

micro-controller radiosensors

battery

mote


5

Hardware - Criteria

• Micro-controller– Reasonably fast

– Low-power

– Multiple I/O options

– Reasonable amount of memory

– Timing capabilities

– Community / support

• Radio-chip– Low-power

– Standards compliant?

– Community / Support


6

Hardware - Microcontrollers

family name arch speedPower

active/asleepRAM ROM Timers I/O used in

ARM

ARM7TDMI 32-bit 115-236MHz 2mW/MHz 8kBa -6 Timers, RTC

3 USART, SPI, 8 10-bit ADC, JTAG

Game Boy Advance,Nintendo DS, iPod

ARM920T 32-bit 180-200MHz 22.4mA/250uA 16kBa 128kBa extensive

UART, USB, Ethernet, 4 USART, I2S, SPI,JTAG

SunSpot

MSP

MSP430f2274 16-bit 16MHz 390uAb/100nAb 1kB 32kB2 timers with 3 CCR

UART/LIN/IrDA/SPI and I2C/SPI

TI eZ430

MSP430f1611 16-bit 8MHz 500uAb/200nAb 10kB 48kB16-bit (3CCR), 16-bit (7CCR)

1 USART (SPI or UART or I2C), 1 USART (SPI or UART)

TelosB,t-mote

AVR ATmega128A 8-bit 16MHz 9.8mAc/1mAc 4kB 128kB2 8-bit, 2 16-bit

2 USART, SPI mica2

a used as cache, primary memory is off-chipb at 1MHzc at 8MHz


7

Hardware - Radios

Brand name 802.15.4 Band sensitivityPower

Tx/Rx/sleepused in

TI

CC2520 Yes 2.4GHz -98dBm 25.8mAa/18.8mA/30nA

CC2420 Yes 2.4GHz -95dBm 17.4mAa/18.8mA/20nATelosB, MICAz, SunSpot EPIC

CC1101 No868/

915MHz-94dBm 16.8mAa/17.1mA/200nA WSN430

CC2500 No 2.4GHz -89dBm 21.2mAa/16.6mA/400nA eZ430-RF2500

AtmelAT86RF230 Yes 2.4GHz -101dBm 16.5mAb/15.5mA/20nA IRIS

AT86RF231 Yes 2.4GHz -101dBm 14mAb/12.3mA/20nA

a at 0dBm transmission powerb at 3dBm transmission power


8

Hardware - Motes

name micro-controller radio battery price

ez430-RF2500 MSP430f2274 CC2500 2 AAA $20 e.a.

eZ430-RF2480 MSP430f2274 CC2480A1 2 AAA $30 e.a.

MICAz AtMega128L CC2420 2 AA $99 e.a.

IRIS AtMega128L AT86RF230 2 AA $119 e.a.

TelosB MSP430f1611 CC2420 2 AA $99 e.a.

RZ USBstick AT90USB1287 AT86RF230 USB $39 e.a.

deUSB2400 AT91SAM7S256 AT86RF231 USB €35 e.a

TI CC2531EMK CC2531 CC2531 USB $49 e.a.


9

Hardware - TelosB

User-defined push

reset

visible light sensor

IR light sensor

humidity sensor

expansion port

internal antenna

external antenna

CC2420

MSP430f1611 (back)

3 LEDs (RGB)

USB for programming

and UART

2 AA (back)Thomas Watteyne @ WCNC 2010

10

eZ430-RF2500

2 LEDspushbutton

CC2500

chip antenna

26MHz crystal

for radio

extension ports

MSP430

USB programmer:• Power• Debug (JTAG) • Interface (serial)


11


4.2 Operating Systems

12

Software - Requirements

• Reduced Memory Footprint– binary code occupies a small amount of ROM

• Hardware Independency– through abstraction of lower layers

• Re-useability– code is divided in chunks communicating through APIs

• Real-time– Easy to measure time (access to timer registers)

– Reasonably fast

– Guaranteed execution timeThomas Watteyne @ WCNC 2010

13

Software - Options

Name Footprint license real-time community

TinyOS(UC

Berkeley)overhead

open-source

best-effort scheduler

large (academia)

Contiki(SICS,

Sweden)overhead

open-source

best-effort scheduler

large (academia)

Think(Orange

Labs)overhead

open-source

experimentalscheduler

modest

uC-OS II overheadfree

academic use

hard real-timescheduler

large (industry)

From scratch optimalopen-source

- -


14

Software - TinyOS

• component-based architecture– code is cut in components

– components communicate through APIs

• component library– TinyOS has been ported to a dozen platforms

– Drivers exist for different micro-controllers and radios

• event-driven execution model– a schedule executes tasks on a FCFS basis

– tasks can be halted by interrupts


15



16

Development Tools

• Firmware development is complex– not complicated!

– develop top-down, always keep an eye on where you’re going

– the vast majority of the cases, you’re wrong (not the compiler, not the protocols)

– bugs are always due to simple errors

– build from atomic building blocks

• Multi-dimensional Debugging– choose a meaning for each LED, and stick with it

– print out error codes, not text

– Use the extension pins with an oscilloscope, the easiest way to measure time

– Use a spectrum analyzer to see on what channels you are occupying

– Use a sniffer to see the packets flying through the air

– A GUI is faster than lines text

– Use a JTAG debugger whenever possible


17

Development Tools• Choosing a scope

– analog channels for energy (put resistor in series with power source)

– the more digital channels, the better

– you don’t need a fast scope

– some oscilloscopes will interpret SPI, I2C, UART (e.g. Tektronic MSO2024)

– cheap USB scopes available

• Spectrum analyzers– are expensive

– can be replaced by a sniffer

– can be replaced by the poor man’s spectrum analyzer

• Sniffer– CC2531 EMK ($49)

• Graphical User Interface– Python+PySerial is a good candidate


18


4.4 Tips & Tricks

19

A MAC Protocol is a State Machine

IDLE

RXUF

RXCW

BACKOFFACK

RXDATATXFIN

TXACK

SENTACK

TXUF

TXCW

RXACK

TXDATA

RXFIN Thomas Watteyne @ WCNC 2010

20

Clock Drift


21

Gotcha’s - Synchronization

1. A sends packet with slot offset α

2. B records the epoch of the time of arrival β

3. B calculates the epoch of the start of the last slot (β- α)

4. B sets its counter register accordingly

A

B

α

β


22

Gotcha’s - Packet Timestamps

1. MSP430 writes packet to CC2420 with error code in timestamp

2. MSP430 triggers the start of the transmission

3. MSP430 records the time of SFD (interrupts)

4. MSP writes to correct timestamp in the Tx buffer

5. Transmission completes

MSP430 CC2420


23

Synchronization


24

Integration into the Internet

NSLU2 by Linksys as a gateway($100)

http://tunnelbroker.net/ for tunnelinginto the IPv6 cloud

(free)

http://sensor.network.com/ by Sunto store your data

(free) http://code.google.com/apis/visualization/http://code.google.com/apis/maps/

to visualize your data onlineThomas Watteyne @ WCNC 2010

http://tunnelbroker.net/�

http://sensor.network.com/�

http://code.google.com/apis/visualization/�

http://code.google.com/apis/maps/�

1


5. Programming Tour

2


5. Programming Tour5.1 Crash-course on the Hardware


5.3 Blinking the LEDs

5.4 Enabling Wireless

5.5 Wireless Chat

5.6 The Importance of CRC

5.7 Poor Man’s Spectrum Analyzer

5.8 Wonderful Wireless Waterfall

5.9 ConclusionsThomas Watteyne @ WCNC 2010

3


5.1 Crash-course on the Hardware

4

MSP430

• “Heart” of the eZ430-RF2500– 16-bit 16MHz RISC

– 32kB ROM, 1kB RAM

– 2 Timers, USCI, 10-bit ADCs

• Debug capabilities using JTAG

• Low Power Operation


5

CC2500• Any frequency on the 2.4-

2.485GHz band– Not 802.15.4-compliant

• Wake-on-radio support– Preamble sampling in

hardware

• 47 configuration registers– Switch Tx/Rx/idle

– TXBUF, RXBUF

– Tx power and frequency

• Follows a state machineSmartRF StudioThomas Watteyne @ WCNC 2010

6

Interconnection

Chip Select

Clock

SPI interfaceinterrupts Thomas Watteyne @ WCNC 2010

7

eZ430-RF2500

2 LEDspushbutton

CC2500

chip antenna

26MHz crystal

for radio

extension ports

MSP430

USB programmer:• Power• Debug (JTAG) • Interface (serial)


8

Extension Pins• P1: GND• P2: VCC_EXT• P3: P2.0 I/O, ACLK, OA010• P4: P2.1 I/O, Timer_A3.INCLK, SMCLK, OA0O• P5: P2.2 I/O, Timer_A3.CCI0B, Timer_A3.TA0, OA• P6: P2.3 I/O, Timer_A3.CCI1B, Timer_A3.TA1, OA• P7: P2.4 I/O, Timer_A3.TA2, OA• P8: P4.3 I/O, Timer_B3.CCI0B, Timer_B3.TB0, OA• P9: P4.4 I/O, Timer_B3.CCI1B, Timer_B3.TB1, OA• P10: P4.5 I/O, Timer_B3.TB2, OA• P11: P4.6 I/O, OA• P12: GND• P13: GDO0 I/O from the CC2500 (configurable)• P14: GDO2 I/O from the CC2500 (configurable)• P15: P3.2 I/O, UC1SOMI• P16: P3.3 I/O, UC1CLK• P17: P3.0 I/O• P18: P3.1 I/O, UC1SIMO Thomas Watteyne @ WCNC 2010

9



10

IAR Kickstart

project file navigator

compile

open files


11

Talking with your mote over “USB”

• Use Windows Device Manager to idenfify the COM port the eZ430-RF2500 is on

• Use PuTTY to connect to that port


12


5.3 Blinking the LEDs

13

Operations on binary data

• A = 0b01101001

• ~A = 0b10010110• A |= 0b00000010 => A=0b01101011• A &=~0b00001000 => A=0b01100001• A ^= 0b10001000 => A=0b11100001• A<<2 => A=0b10100100• A>>2 => A=0b00011010


14

I/O port registers

• P1DIR: direction, 0=in, 1=out

• P1OUT: set output

• P1IN: read input


15

A steady LED

led_steady

Disable watchdog

timer

P1.0 and P1.1 as output

P1.0=1 and P1.1=1

Continue executing

#include "io430.h"

#include "in430.h"

int main( void )

{

WDTCTL = WDTPW + WDTHOLD;

P1DIR |= 0x03;

P1OUT |= 0x03;

while(1);

}


16

Active Waiting Loop

led_loop

#include "io430.h"

#include "in430.h"

int main( void )

{


int i;

P1DIR |= 0x03;

while (1) {

P1OUT ^= 0x03;

for (i=0;i<10000;i++) {

__no_operation();

}

}

}

P1.0 and P1.1 as output

Change Led state (aka toggle)


17

Interrupt

• Interrupt only when both– General interrupt enabled in status register

– Specific interrupt enabled in specific register

• Interrupt Service Routine written as:#pragma vector=TIMERA0_VECTOR

• ISR sometimes needs to clear an interrupt flag in a specific register


18

Button-Driven Toggle Through Interrupts

led_button

#include "io430.h"#include "in430.h"int main( void ){WDTCTL = WDTPW + WDTHOLD;P1DIR |= 0x03;P1DIR &= ~0x04;P1REN |= 0x04;P1OUT |= 0x04;P1IE |= 0x04;__bis_SR_register(GIE);while(1);

}

#pragma vector=PORT1_VECTOR__interrupt void Port_1 (void){P1IFG &= ~0x04;P1OUT ^= 0x03;

}

P1.2 as input

enable resistor (for button)

enable interrupt for P1.2 globally enable

interrupts (do this last)

Executed when interrupt from P1

Actual function name has no importance

Clear interrupt flag (mandatory)

Toggle LEDsThomas Watteyne @ WCNC 2010

19

Timer

• A timer is a counter which– Counts in a certain way (up, down, continuous)

– At every clock tick

• Can be used in two ways:– Triggers interrupts when reaching a given value

(compare mode)

or

– Records its timer value on other interrupts(capture mode)


20

Timer-Driven Toggle Through Timer Interrupts

led_timer

#include "io430.h"

#include "in430.h"

int main( void )

{


P1DIR |= 0x03;

TACCTL0 = CCIE;

TACCR0 = 1000;

TACTL = TASSEL_1 + MC_1;

__bis_SR_register(GIE+LPM3_bits);

}

#pragma vector=TIMERA0_VECTOR

__interrupt void Timer_A (void)

{

P1OUT ^= 0x03;

}

Timer_A interrupt enable Capture Compare

to 1000

Count following ACLK

Count in up mode

interrupt interrupt

Globally enable interrupt

low power mode, waiting for interrupts

Executed at each Timer_A interruptThomas Watteyne @ WCNC 2010

21


5.4 Enabling Wireless

22

Simple Tx/Rx

txrx_simple

#include "mrfi.h"

int main(void)

{

BSP_Init();

P1REN |= 0x04;

P1OUT |= 0x04;

P1IE |= 0x04;

MRFI_Init();

MRFI_WakeUp();

MRFI_RxOn();


}

void MRFI_RxCompleteISR()

{

P1OUT ^= 0x02;

}

#pragma vector=PORT1_VECTOR

__interrupt void Port_1 (void)

{

P1IFG &= ~0x04;

mrfiPacket_t packet;

packet.frame[0]=8+20;

MRFI_Transmit(&packet, MRFI_TX_TYPE_FORCED);

P1OUT ^= 0x01;

}

Init MSP430 (clock, leds, button)

Init CC2500 (pins, SPI, registers)

Start CC2500 oscill. (IDLE state)

CC2500 to RX state

low power mode, waiting for interrupts

Executed when packet received

(“meta” interrupt declaration)

Executed when button pushed

clear button interrupt flag

declare packet w. max length

declare useful length

copy to cc2500 TXFIFO and send

Length (1B) Source (4B) Destination (4B) Payload (Length-8 bytes long)


23

#include "mrfi.h"

int main(void)

{

BSP_Init();

P1REN |= 0x04;

P1OUT |= 0x04;

P1IE |= 0x04;

MRFI_Init();

MRFI_WakeUp();

MRFI_RxOn();


}


{

P1OUT ^= 0x02;

}



{

P1IFG &= ~0x04;




P1OUT ^= 0x01;

}

Change Channel

txrx_simple

#include "radios/family1/mrfi_spi.h"

mrfiSpiWriteReg(CHANNR,0x10);

Removing this line cause continuous

transmissions


24

Continuous Transmission


25

#include "mrfi.h"

int main(void)

{

BSP_Init();

P1REN |= 0x04;

P1OUT |= 0x04;

P1IE |= 0x04;

MRFI_Init();

MRFI_WakeUp();

MRFI_RxOn();


}


{

P1OUT ^= 0x02;

}



{

P1IFG &= ~0x04;




P1OUT ^= 0x01;

}

Change Transmission Power

txrx_simple


mrfiSpiWriteReg(PATABLE,0xFF);


26

Impact of Transmission Power

setting power current

0X84 -24dBm 16.1mA

0x55 -16dBm 16.5mA

0x97 -10dBm 18.3mA

0xA9 -4dBm 22.6mA

0xFE 0dBm 27.6mA

0xFF 1dBm 27.9mA


27


5.5 Wireless Chat

28

Wireless Chat [1/3]

chat


#include "mrfi.h"

uint8_t index_output = 9;

mrfiPacket_t packetToSend;

int main(void)

{

BSP_Init();

MRFI_Init();

P3SEL |= 0x30; // P3.4,5 = USCI_A0 TXD/RXD

UCA0CTL1 = UCSSEL_2; // SMCLK

UCA0BR0 = 0x41; // 9600 from 8Mhz

UCA0BR1 = 0x3;

UCA0MCTL = UCBRS_2;

UCA0CTL1 &= ~UCSWRST; // Initialize USCI state machine

IE2 |= UCA0RXIE; // Enable USCI_A0 RX interrupt

MRFI_WakeUp();

MRFI_RxOn();

index_output=0;


}

Enable UART


29

Wireless Chat [2/3]


{

uint8_t i;

P1OUT ^= 0x02;


MRFI_Receive(&packet);

char output[] = {" "};

for (i=9;i<29;i++) {

output[i-9]=packet.frame[i];

if (packet.frame[i]=='\r') {

output[i-9]='\n';

output[i-8]='\r';

}

}

TXString(output, (sizeof output));

}

when received a packet

Copy RXFIFO into “packet”

write over serial portnewline(for PuTTY)

chat Thomas Watteyne @ WCNC 2010

30

Wireless Chat [3/3]

#pragma vector=USCIAB0RX_VECTOR

__interrupt void USCI0RX_ISR(void)

{

char rx = UCA0RXBUF;

uint8_t i;

packetToSend.frame[index_output]=rx;

index_output++;

if (rx=='\r' || index_output==29) {

packetToSend.frame[0]=28;

MRFI_Transmit(&packetToSend, MRFI_TX_TYPE_FORCED);

index_output = 9;

for(i=9;i<29;i++) {

packetToSend.frame[i]=' ';

}

P1OUT ^= 0x01;

}

P1OUT ^= 0x02;

TXString(&rx, 1);

}

when received one character

over serial port

copy serial input buffer to “rx”

Append to the packet being constructed

newline or packet fullcopy to TXFIFO,

trigger Tx

re-initialize

echo over serial portchat Thomas Watteyne @ WCNC 2010

31


5.6 The Importance of CRC

32

CRC: Cyclic Redundancy Check

• If PKTCTRL0.CRC_EN=1:– At Tx, data is hashed and result append to the

packet as a 2-byte field

– At Rx, data is hashed and result compared to CRC field, packet dropped if fails

• How CRC works– Calculate the remainder

of a (binary) division

– In CC2500,CRC-16-IBM (x16 + x15 + x2 + 1)

Single bit errors 100%

Double-bit errors 100%

Odd-Numbered errors 100%

Burst Errors Shorter than 16 bits 100%

Burst Errors of exactly 17 bits 99.9969%

All other burst errors 99.9984%


33

CRC: Cyclic Redundancy Check1101001110110010110110001110110010110111011101100101101011110110010110000110110010110001101100101100110110010110110110010110110100101101100010110111010110101

• Pick a CRC length– e.g. 3 bits

• Pick a polynom– e.g. x4+x+1 (1011)

– (Always a leftmost 1!)

• While bits in data– Write under leftmost data bits

– iif leftmost data bit is 1, XOR(leftmost bit always turns to 0)

– Shift right one place

• Collect 3-bit CRCThomas Watteyne @ WCNC 2010

34

The Importance of CRC [1/3]

crc


#include "mrfi.h"

mrfiPacket_t packetToSend;

int main(void)

{

BSP_Init();

P1REN |= 0x04;

P1OUT |= 0x04;

P1IE |= 0x04;

MRFI_Init();

mrfiSpiWriteReg(PATABLE,0xBB);

mrfiSpiWriteReg(PKTCTRL0,0x41);

P3SEL |= 0x30;

UCA0CTL1 = UCSSEL_2;

UCA0BR0 = 0x41;

UCA0BR1 = 0x3;

UCA0MCTL = UCBRS_2;

UCA0CTL1 &= ~UCSWRST;

MRFI_WakeUp();

MRFI_RxOn();


}

Enable UART

reduce the TxPower for more frequent errors

disable CRC


35



{

uint8_t i;

P1OUT ^= 0x02;



char output[] = {" \r\n"};

for (i=9;i<packet.frame[0];i++) {

output[i-9]=packet.frame[i];

}

TXString(output, (sizeof output));

}

when receiving a packet

Copy RXFIFO to “packet”

format string

send string over serial

crc Thomas Watteyne @ WCNC 2010

36




{

P1IFG &= ~0x04;

char character = 'a';

uint8_t index;


for (index=9;index<30;index++) {

packet.frame[index]=character++;

}

packet.frame[0]=++index;


P1OUT ^= 0x01;

}

when button is pressed

comment out for continuous Tx

Fill frame with ‘abcdef…’

Copy to TXFIFO and send

crc Thomas Watteyne @ WCNC 2010

37


5.7 Poor Man’s Spectrum Analyzer

38

Poor Man’s Spectrum Analyzer [1/2]

#include "mrfi.h"


void print_rssi(int8_t rssi)

{

char output[] = {" 000 "};

if (rssi<0) {output[0]='-';rssi=-rssi;}

output[1] = '0'+((rssi/100)%10);

output[2] = '0'+((rssi/10)%10);

output[3] = '0'+ (rssi%10);

TXString(output, (sizeof output)-1);

}


{

}

prints out a signed int as characters

spectrum

send string over serial

we’re not interested in actually receiving

packets


39

int main(void)

{

int8_t rssi;

uint8_t channel;

BSP_Init();

MRFI_Init();

P3SEL |= 0x30;


UCA0BR0 = 0x41;

UCA0BR1 = 0x3;

UCA0MCTL = UCBRS_2;


MRFI_WakeUp();

__bis_SR_register(GIE);

while(1) {

for (channel=0;channel<200;channel++) {

MRFI_RxIdle();

mrfiSpiWriteReg(CHANNR,channel);

MRFI_RxOn();

rssi=MRFI_Rssi();

print_rssi(rssi);

}

TXString("\n",1);

}

}

Poor Man’s Spectrum Analyzer [2/2]

spectrum

change channel

Enable UART

switch radio on

read current noise level


40

Poor Man’s Spectrum Analyzer

spectrum.py Thomas Watteyne @ WCNC 2010

41


5.8 Wonderful Wireless Waterfall

42

Wonderful Wireless Waterfall

• Receiver listens

• When button pressed sender sends a burst of packets– 100 packets with counter from 1 to 100

– 20 packets with counter to 101

• When receiving a packet– If packet counter <101, increment a counter and

store the RSSI

– For the first packet with counter==101, display “average RSSI – channel success probability”


43

Wonderful Wireless Waterfall [1/4]

#include "mrfi.h"

uint8_t counter, num_received, bool_counting;

int16_t cumulative_rssi;


void print_probability(int16_t cumulative_rssi, uint8_t number)

{

char output[] = {" 000 0.00\n"};

if (cumulative_rssi<0) {

output[0]='-';

cumulative_rssi=-cumulative_rssi;

}

output[1] = '0'+((cumulative_rssi/100)%10);

output[2] = '0'+((cumulative_rssi/10)%10);

output[3] = '0'+ (cumulative_rssi%10);

output[5] = '0'+((number/100)%10);

output[7] = '0'+((number/10)%10);

output[8] = '0'+ (number%10);

TXString(output, (sizeof output)-1);

}

e.g. “-55 0.75”

Prepare string transmit string over serial

waterfall Thomas Watteyne @ WCNC 2010

44


int main(void)

{

BSP_Init();

P1REN |= 0x04;

P1IE |= 0x04;

MRFI_Init();

mrfiSpiWriteReg(PATABLE,0x50);

P3SEL |= 0x30;


UCA0BR0 = 0x41;

UCA0BR1 = 0x3;

UCA0MCTL = UCBRS_2;


MRFI_WakeUp();

MRFI_RxOn();


}


enable serial communication

Wait for interrupts in low power mode


45



{

P1OUT ^= 0x02;


counter = packet.frame[9];

if (counter==101) {

if (bool_counting == 1) {

print_probability(cumulative_rssi/num_received,num_received);

}

bool_counting=0;

num_received=0;

cumulative_rssi=0;

} else {

bool_counting=1;

num_received++;

cumulative_rssi+=(int8_t) packet.rxMetrics[0];

}

}

When I receive a packet


46



__interrupt void interrupt_button (void)

{

P1IFG &= ~0x04;

P1OUT ^= 0x01;



for (counter=1;counter<101;counter++){

packet.frame[9]=counter;


}

for (counter=0;counter<20;counter++){

packet.frame[9]=101;


}

}



47

Wonderful Wireless Waterfall

waterfall.py Thomas Watteyne @ WCNC 2010

48


5.9 Conclusions

49

Conclusions

• A building block approach– Blinking LEDs

– Interacting with button

– Measuring time

– Interacting with the serial port

– Sending/receiving packets

• More?– http://cnx.org/content/col10684/latest/

• Contribute!– [email protected]


http://cnx.org/content/col10684/latest/�

mailto:[email protected]�

1

Thomas Watteyne @ WCNC 2010 1/TBC

6. Conclusions and Road Ahead

2

Conclusions

Thomas Watteyne @ WCNC 2010 2

• General:– ‘R’ is rather focused on large-scale and highly resource constrained

– ‘D’ is rather focused on connection to Internet to facilitate Internet of Things

• Industrial Developments:– business takes off slower than anticipated, possibly because of defragmentation

– endless proprietary solutions available with little inter-operability

• Standardization Activities:– IEEE have standardized a solution for robust communication

– IETF is enabling seamless integration into the Internet

– Open source implementations as enablers

3

Multirate IEEE802.15.4

S. Lanzisera, A. Mehta, K. Pister, "Reducing Average Power in Wireless Sensor Networks Through Data Rate Adaptation," IEEE International Conference on Communications (ICC), June 2009.


4


• Decrease transmit power– Inefficient

• Variable Rate Signaling– Use excess SNR to send messages faster

– Usually done to increase throughputAdditional

SNRPA Energy

SavingsData Rate Variable

Rate Savings

0 dB 0% 250 kbps 0%

2.6 dB 16% 500 kbps 48%

5.6 dB 31% 1000 kbps 72%

14.1 dB 55% 2000 kbps 84%Thomas Watteyne @ WCNC 2010 4

5



6


7


“I do not think that the wireless waves that I have discovered will have any practical application.”

- Heinrich Hertz 1890

Building Tomorrow’s Internet of Things: Latest Standardization Trends andHands-on Programming Tutorial

Thomas WatteyneBerkeley Sensor and Actuator Center


WCNC, 18 April 2010

Thank you.

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