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Sensor Node Architectures. EE202A Lecture Oct 1, 2003 Ram Kumar {ram@ee.ucla.edu}. Sensor Network Vision. Ack: Jason Hill, UC Berkeley. SENSING SUB-SYSTEM. PROCESSING SUB-SYSTEM. COMMUNICATION SUB-SYSTEM. ACTUATION SUB-SYSTEM. POWER MGMT. SUB-SYSTEM.

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sensor node architectures

Sensor Node Architectures

EE202A Lecture

Oct 1, 2003

Ram Kumar {ram@ee.ucla.edu}

sensor network vision
Sensor Network Vision

Ack: Jason Hill, UC Berkeley

sensor node architecture components

SENSING

SUB-SYSTEM

PROCESSING

SUB-SYSTEM

COMMUNICATION

SUB-SYSTEM

ACTUATION

SUB-SYSTEM

POWER MGMT.

SUB-SYSTEM

Sensor Node Architecture Components
  • Small physical size: 1 mm3
  • Low Power Consumption: < 50 mW
  • Resource Constrained: 8 MHz, 4 Kb
diversity in platforms

Capabilities

StarGate

MK - II

iBadge

MICA Mote

Size, Power Consumption, Cost

Diversity in Platforms
design lineage of motes
Design Lineage of Motes
  • COTS dust prototypes (Kris Pister et al.)
  • weC Mote (~30 produced)
  • Rene Mote (850+ produced)
  • Dot (1000 produced)
  • Mica node ( 5000+ produced)
  • Mica2 (Current)
  • Spec (Prototype)

Ack: Jason Hill, UC Berkeley

processing sub system
Processing Sub-System
  • Functions
    • Application Execution
    • Resource Management
    • Peripheral Interaction
  • Atmel AVR ATMEGA128L
    • RISC Architecture
    • 8 bit ALU/data-path
    • 128 Kb FLASH - Code
    • 4 Kb SRAM - Data
    • Multiple peripherals

Details are available in the ATMEGA128L Datasheet

avr interrupts
AVR Interrupts
  • Interrupts are triggers that can be used to monitor an event
    • One could use polling but, in most cases this has additional software overhead
    • Better to have the peripherals “interrupt” the controller when an event occurs ( e.g data availability, change of a condition etc)
    • Interrupts can be edge triggered (falling or rising edge) or level triggered (signal goes high or low)
  • On the AVR microcontroller, interrupts are vectored
avr timers
AVR Timers

Timer0

8 - bit

  • Multiple Timers
  • Multiple Clock Sources
    • CPU Clk
    • Real Time Clk – 32 KHz
    • Pre-scaled Clk from above sources
  • Multiple Interrupts
    • Timer Overflow
    • Output Compare
  • Functions
    • Periodic sampling pulses
    • Waveform generation

Timer2

Timer1

16 - bit

Timer3

avr peripherals
AVR Peripherals
  • UART
    • Serial communication with the PC
  • SPI – Serial Peripheral Interface
    • Synchronous serial communication
    • Interface to Radio in the Mote
  • ADC
    • Analog – Digital Converter
    • Digitizing sensor readings
  • I/O Ports
    • General Purpose Input Output pins (GPIO)
    • Used to light up LEDs in Mote
avr power management
AVR Power Management
  • Low Power operation – 15 mW @ 4 MHz
  • Multiple Sleep Modes
    • Sleep Modes: Shutdown unused components
    • Idle Mode – 6 mW
      • CPU OFF, all peripherals ON
      • CPU “woken up” by interrupts
    • Power Down Mode – 75 uW
      • CPU and most peripherals OFF
      • External Interrupts, 2 Wire Interface, Watchdog ON
    • Power Save Mode – 120 uW
      • Similar to Power Down
      • Timer0 continues to run “asynchronously”
sensing sub system
Sensing Sub-System
  • Functions
    • Sampling physical signals/phenomena
  • Different types of sensors
    • Photo-sensor
    • Acoustic Microphone
    • Magnetometer
    • Accelerometer
  • Sensor Processor Interface
    • 51 Pin Connector
    • ON-OFF switches for individual sensors
    • Multiple data channels

Sensors consume power

Turn them off after sampling !

  • Useful Link/Resources
  • The pin definitions of 51-pin connector
  • Check out the HW schematics
  • http://webs.cs.berkeley.edu/tos/
  • Look under Hardware Designs tab
  • Details of other sensor boards
  • Check them out at the XBow website
  • http://www.xbow.com
communication sub system
Communication Sub-System
  • Functions
    • Transmit – Receive data packets wirelessly
    • Co-ordinate/Network with other nodes
  • Implementation
    • Radio
      • Modulation – Demodulation
      • Two types of radios: RFM, ChipCon CC1000
      • RFM: Mica & predecessors
      • CC1000: Mica2 onwards
    • AVR
      • Protocol Processing
wireless comm basics
Wireless Comm. Basics
  • All wireless systems follow these steps
  • Radios have varying capabilities
    • RFM – Simple radio, only modulates-demodulates bits
    • CC1000 – Performs Machester coding-decoding and synchronization also
mica rfm avr interface

SPI

RFM

RADIO

Data I/O

SPI CLK

Timer0

CTL0

CTL1

Mica - RFM AVR Interface
  • Data Interface
  • Periodic waveform generated by Timer0
  • Waveform fed as clk to SPI unit
  • SPI samples Data I/O line periodically during Rx
  • SPI shifts out data during Tx
  • Radio only performs modulation-demodulation
  • Control Interface
  • GPIO Pins of AVR
  • Two Control lines decide
  • Radio state
mica2 cc1000 avr interface

SPI

CHIPCON

CC1000

RADIO

Data I/O

DCLK

PCLK

PDATA

PALE

Mica2 – CC1000 AVR Interface
  • Data Interface
  • SPI CLK generated by radio
  • Radio Rx data available as a bit-stream
  • Radio performs channel encoding-decoding
  • and bit-synchronization
  • Control Interface
  • GPIO Pins of AVR
  • Simulate SPI in S/W
  • PCLK: Program Clock
  • PDATA: Program Data
  • PALE: R/W Select
  • Radio state written to registers
  • in radio
radio power management
Radio Power Management
  • Radio has very high power consumption
    • Tx power is range dependant - 49.5 mW (0 dBm)
    • Rx power is also very high - 28.8 mW
    • Power-down sleep mode - 0.6 uW
    • Above data for CC1000, 868 MHz (Check out CC1000 data-sheets for more numbers)
  • Radio power management critical
    • Idle state channel monitoring power = Rx Power
    • Put radio to sleep when not in use
    • But then, how do we know when somebody is trying to contact us ?
medusa mk ii overview

PALOS

Medusa MK-II Overview

ARM/THUMB 40MHz

Running uCos-ii

RS-485 &

External Power

ADXL 202E

MEMS Accelerometer

MCU I/F

Host Computer, GPS, etc

UI: Pushbuttons

Ack: Andreas Savvides, NESL UCLA

http://nesl.ee.ucla.edu/projects/ahlos/

references
References
  • Atmel ATMEGA128L DataSheet (www.atmel.com)
  • ChipCon CC1000 DataSheet (www.chipcon.com)
  • RFM TR1000 DataSheet (www.rfm.com)
  • XBow Corp. (www.xbow.com)
  • Jason Hill et. all, “System Architecture directions for Networked Sensors”, ASPLOS 2000
  • Jason Hill et. all, “A wireless embedded sensor architecture for system-level optimization”, ISCA
  • Joe Polastre et. All, “Wireless Sensor Networks for Habitat Monitoring”, WSNA 2002
  • TinyOS Web – (http://www.tinyos.net)