Transcript hardware platforms

WSN Hardware Platforms
Vinod Kulathumani
Lecture uses some slides from tutorials
prepared by authors of these platforms
Factors
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Cost
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Lifetime (when almost always on, when almost always off)
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Performance:
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Speed (in ops/sec, in ops/joule)
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Comms range (in m, in joules/bit/m)
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Memory (size, latency)
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Capable of concurrent operation
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Reliability, security, size, packaging
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Types of sensor platforms
1.
RFID equipped sensors
2.
Smart-dust tags
3.
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typically act as data-collectors or “trip-wires”
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limited processing and communications
Mote/Stargate-scale nodes
•
4.
more flexible processing and communications
More powerful gateway nodes, potentially using wall power
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Block diagram – sensor node
SENSING
SUB-SYSTEM
PROCESSING
SUB-SYSTEM
COMMUNICATION
SUB-SYSTEM
ACTUATION
SUB-SYSTEM
POWER MGMT.
SUB-SYSTEM
SECURITY
SUB-SYSTEM
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Processing Subsystem: Microcontroller
• von Neumann architecture (same address and data bus)
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typical 4 bit, 8 bit, 16 bit or 32 bit architectures
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speed 4 MHz-400MHz with 10-300 or more MIPS
• operate at various power levels:
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fully active: 1 to 50 mW
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sleep (memory standby, interrupts active, clocks active, cpu off)
• latency of wakeup is an issue
• fixed point or floating point operations
• multiple processors may be used (potentially on same core)
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could be DSP, FPGA
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Processing Subsystem: Memory
• SRAM: typical, 0.5KB-64MB
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Typical power consumption
retained: ~100ua; read/write: ~10ma if separate chip
retained: 2ua-100ua, read/write:~5ma if in core
• EEPROM:4KB-512KB, often used as program store
• Flash: 256KB-1GB or beyond
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Typical power consumption
retained: negligible; read/write: ~7/20ma
erase operation is expensive
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Large flashes are outside of core
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Sensor Subsystem
• Multiple types of sensors may be used:
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Environmental: pressure, gas composition, humidity, light…
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Motion or force: accelerometers, rotation, microphone, piezoresistive
strain, position…
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Electromagnetic: magnetometers, antenna, cameras…
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Chemical/biochemical
• Digital or analog output
• MEMS enabling size, cost and power miniaturization; nano coming
• Components: Transducer, Analog signal conditioning circuits, ADC, DSP
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Sensor Subsystem Considerations
• Energy consumption in active/passive mode is relevant
• Sampling rate (1Hz or lower to 5Khz or higher)
• Signal resolution
ADC bits: 8, 10, 12, 16, 20 bit (affects cost)
 On-chip or not
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• Wakeup circuits help reduce power consumption of processing
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
But startup time/power cycling latencies become an issue
(~1ms-1000ms or higher)
• Interference, cross-talk
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Actuation Subsystem
• Types:
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Leds, buzzers, motors, sliders, pumps, gears, solenoids…
• Energy consumption (idle: O(uW); active ~1-40 mW)
• Startup time (~1ms-1000ms or higher)
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Power Management Subsystem
• Voltage regulator
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typical ranges: 1.8V, 3.3V, 5V
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multiple voltages for various subsystem/power levels
• Gauges for voltage or current
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battery monitor (allows software to adapt computation)
• Control of subsystems wakeup/sleep
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latency is key in driving down the duty cycle
• Control of platform clock rate, processor voltage
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Power Management Subsystem
• Energy source:
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


volume energy density, mass energy density
peak and average current (discharge rate)
NiCd, NiMH, LiIon, LiPolymer, fuel cells
DC-DC conversion
• Charger/energy harvesting/scavenging
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

solar, wind, vibration, heat
account for variations in supply
number of charge/discharge cycles have limits
• Power supply may be external
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Communication Subsystem
Considerations:
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speed, range, power consumption, startup time
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energy efficiency: joules/bit/m
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signal propagation and interference characteristics
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difference between receive power versus transmit power
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not all devices need a receiver
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choice of power level
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antenna design
 matching impedance
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Security Subsystem
Some COTS radios offer security features
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Outline
• Hardware
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RFID, Spec
Mica2, XSM, Telos
Stargate
Intel imote2
SunSpots
Sentilla
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Grain-sized nodes
 Powered by inductive coupling to a transmission from a
reader device to transmit a message back
 Available commercially at very low prices
× Computation power is severely limited
×
Can only trasmit stored unique id and variable
× Hard to add any interesting sensing capability
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Spec Mote
(2003)
• size: 2x2.5mm, AVR RISC core, 3KB memory, FSK radio (CC1000),
• encrypted communication hardware support, memory-mapped active
messages
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Matchbox-sized nodes
• Mica series, XSM node, Telos
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8-bit microprocessor, 4MHz CPU

ATMEGA 128, ATMEL 8535, or Motorola HCS08
• ~4Kb RAM
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holds run-time state (values of the variables) of the program
• ~128Kb programmable Flash memory
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
•
holds the application program
Downloaded via a programmer-board or wirelessly
Additional Flash memory storage space up to 512Kb.
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Mica2 and Mica2Dot
• ATmega128 CPU
1 inch
– Self-programming
• Chipcon CC1000
– FSK
– Manchester encoding
– Tunable frequency
• Low power consumption
– 2 AA battery = 3V
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Basic Sensor Board
• Light (Photo)
• Temperature
• Prototyping space for
new hardware designs
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Mica Sensor Board
• Light (Photo)
• Temperature
• Acceleration
– 2 axis
– Resolution: ±2mg
• Magnetometer
– Resolution: 134mG
• Microphone
• Tone Detector
• Sounder
– 4.5kHz
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PNI Magnetometer/Compass
• Resolution: 400 mGauss
• Three axis, under $15 in large quantities
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Ultrasonic Transceiver
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•
•
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Used for ranging
Up to 2.5m range
6cm accuracy
Dedicated
microprocessor
• 25kHz element
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MicaDot Sensor Boards
“Dot” sensorboards (1”diameter)
HoneyDot: Magnetometer
Resolution: 134 mGauss
Ultrasonic Transceiver
Weather Station
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XSM node platform
• Derived from Mica2 mote
• Better sensor & actuator range
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–
–
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4 Passive Infrared: ~ 25m for SUV
Sounder:
~10m
Microphone:
~ 50m for ATV
Magnetometer:
~ 7m for SUV
• Better radio range
~30m
• Other features:
– Grenade timer
– Wakeup circuits (Mic, PIR)
– Adjustable frequency sounder
– Integrated Mag Set/Reset
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Telos Platform
• Low Power

Minimal port leakage
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Hardware isolation and buffering
• Robust
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Hardware flash write protection
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Integrated antenna (50m-125m)
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Standard IDC connectors
• Standards Based
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USB
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IEEE 802.15.4 (CC2420 radio)
• High Performance
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10kB RAM, 16-bit core, extensive double buffering
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12-bit ADC and DAC (200ksamples/sec)
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DMA transfers while CPU off
• 8 MHz TI MSP 430 microcontroller
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Telos
Meeting the Low Power Goal
All values measured at room temperature (approximately 25oC) at 3V supply voltage
Source: “Telos: Enabling Low Power Wireless Sensor Network Research”
To appear, IPSN/SPOTS, April 2005
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Brick-sized node: Stargate
• Mini Linux computers communicating via 802.11 radios
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
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Computationally powerful
High bandwidth
Requires more energy (AA infeasible)
• Used as a gateway between the Internet and WSN
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III. XSS (Stargate) Node Platform
802.11b wireless
card , 23dBm
(high power),
~500m range
Intel’s Stargate
– 400 MHz processor
– 64 MB RAM
– 32 MB Flash
25¢
GPS receiver
~10m
accuracy
waterproof packaging
w/ integrated
antenna mast & base
Mica-2
connects
to XSMs
8 dBi collinear omnidirectional antenna
105Ah lead acid battery !
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imote2
• Intel Xscale Processor PXA271



13 MHz to 416 MHz
Intel MMX DSP coprocessor
Computing resource like that of Stargate
• 32 Mb SDRAM, 32 MB flash
• 802.15.4 radio
• Comes with battery board

Additional rechargeable ones attachable
• Supports Linux, TinyOS and SOS operating systems
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Separate .NET edition available, installed with .NET microframework
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imote2 - Power
• Advanced signal processing possible
• Yet low power consumption
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
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Radio is low power
Processor can tuned down when not needed
Many power save modes available
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Beagleboard
ARM Core plus DSP
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Java based platform: Sunspot
• Sun labs project
• Easy development

Can use netbeans and Eclipse to develop and debug
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Java based platform: Sunspot
• 180MHz 32-bit ARM920T core processor
• 512K RAM and 4M Flash
• 2.4GHz radio with an integrated antenna
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
Radio is TI CC2420 (formerly ChipCon)
IEEE 802.15.4 compliant
• USB interface and LEDs
• Sensors
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
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3-axis accelerometer (with two range settings: 2G or 6G)
Temperature, light sensors
6 analog inputs
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Java based platform: Sunspot
Software
• No operating system
• Runs Java Squawk ME virtual machine on bare metal!
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

provides basic OS functionality
VM operates out of flash memory
device drivers in java
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Java based platform: Sentilla
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8 MHz processor, CC 2420 radio
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Low power, low resource
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10 times smaller JVM than Squawk
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Reading
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The platforms enabling wireless sensor networks
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System architecture directions for networked sensors
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Assignment 1b
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Review of new hardware platforms
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•
Arduino
WaspMote
Shimmer
Dust Networks
ATMEL AVR Raven
EMBER
Particle
Focus on
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Power consumption, memory, processing
Interfaces
Sensor and actuator integration
Prototype applications and demonstrations
User base
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References
• TMote DataSheet (www.moteiv.com)
• Atmel ATMEGA128L DataSheet (www.atmel.com)
• ChipCon CC1000 DataSheet (www.chipcon.com)
• RFM TR1000 DataSheet (www.rfm.com)
• XBow Corp. (www.xbow.com)
• Sentilla (www.sentilla.com)
• SunSpotWorld (www.sunspotworld.com)
• Andreas Savvides (http://www.eng.yale.edu/enalab/courses/eeng460a)
• http://nesl.ee.ucla.edu/courses/ee202a/2003f/lectures/GP03_Vijay.ppt
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