Telos Fourth Generation WSN Platform Joseph Polastre UC Berkeley Moteiv Corporation Develop control abstraction

Design Principles for WSN Platforms (from HotChips 2004) Wireless Sensor Networks Must operate for many years Need low duty cycles to achieve long lifetimes Key to Low Duty Cycle Operation: Sleep – majority of the time Wakeup – quickly start processing Active – minimize work & return to sleep

Sleep Majority of time, node is asleep Minimize sleep current through >99% Minimize sleep current through Isolating and shutting down individual circuits Using low power hardware Need RAM retention Run auxiliary hardware components from low speed oscillators (typically 32kHz) Perform ADC conversions, DMA transfers, and bus operations while microcontroller core is stopped

Wakeup Overhead of switching from Sleep to Active Mode Microcontroller Radio (FSK) 292 ns 10ns – 4ms typical 2.5 ms 1– 10 ms typical

Active Microcontroller Radio External Flash (stable storage) Fast processing, low active power Avoid external oscillators Radio High data rate, low power tradeoffs Narrowband radios Low power, lower data rate, simple channel encoding, faster startup Wideband radios More robust to noise, higher power, high data rates External Flash (stable storage) Data logging, network code reprogramming, aggregation High power consumption Long writes Radio vs. Flash 250kbps radio sending 1 byte Energy : 1.5mJ Duration : 32ms Atmel flash writing 1 byte Energy : 3mJ Duration : 78ms

Telos New design started in September 2003 Principles >12 months of work by 2+ grad students Principles Easy to use Standards based Lowest power consumption Low standby/active current, short wakeup times

Telos Platform Low Power Robust Standards Based High Performance Minimal port leakage Hardware isolation and buffering Robust Hardware flash write protection Integrated antenna (50m-125m) Standard IDC connectors Standards Based USB IEEE 802.15.4 (CC2420 radio) High Performance 10kB RAM, 16-bit core, extensive double buffering 12-bit ADC and DAC (200ksamples/sec) DMA transfers while CPU off

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

Telos Performance 200ksamples/sec sampling rate, DMA transfers, DAC Increased performance & functionality over existing designs New “link quality indicator” predicts average packet loss Flat field range test @ 4” off ground (125m @ 1m elevation) Distance (ft) Packet Success Average LQI RSSI

Prometheus: Perpetually Powered Telos Duty Cycle Light Required System Lifetime 1% 5 hrs / 1 mo 43 years 10% 5 hrs / 4 days 4 years 100% 10 hrs / 1 day 1 year Solar energy scavenging system for Telos Super capacitors buffer energy Lithium rechargeable battery as a emergency backup Possible due to low voltage (1.8V) and low power (<15mW) consumption of Telos Visit the poster later today… Source: “Perpetual Environmentally Powered Sensor Networks” To appear, IPSN/SPOTS, April 2005

Visit the demo later today… Experimentation with the Telos Platform: Telos Sensor Board Polastre and Dutta Event-driven sensorboard design Configurable Sensors with Interrupt Wakeup Microphone -- Sampling up to 200ksamples/second Variable gain, noise gating, low pass filter, configurable wakeup Speaker – Full dynamic range 100-20000Hz >700mW output to 8 ohm speaker, 100-20000Hz Accelerometer -- +/-5g, interrupts on light taps to heavy shaking Light sensor -- Photodiode with amplifier, configurable gain Low Voltage operation matches Telos design principles Lithium Ion battery recharged by USB Visit the demo later today…

Telos Designs and Availability Designs and Layout provided to the open source community under BSD license Available at TinyOS.net Many Telos clones now exist Many other Telos projects in the works Telos AC adapter, Telos fire alarm system… Tmote is the family of motes that use Telos as the reference design Commercialized by Moteiv Corporation