Energy Management in T2

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Energy Management in T2
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Motivation

• If the application must explicitly invoke power
  control operations, this will introduce
  application code complexity
• Let the OS automatically minimize energy
  consumption - Integrated Concurrency and Energy
  Management (ICEM)

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ICEM (Integrated Concurrency and Energy
Management)

• Most WSN OS are completely event-driven
• Diverse peripherals
• An application simply needs to make a set of
  asynchronous system calls and let OS schedule the
  underlying operations
• Power locks
• When a client acquires a drivers power lock
  ICEM has powered and configured the hardware for
  the client
• When a power lock is idle, ICEM powers down the
  underlying hardware

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Example Implementations in T2

• Lock Interface is named Resource in T2
• Arbiter Configure Interface is named
  ResourceConfigure in T2
• DefaultOwner Interface is named
  ResourceDefaultOwner in T2

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Example Applications based on TelosB

• Every five minutes, the application samples four
  sensors (photo active, total solar, temperature,
  and humidity) and logs the readings in flash with
  a sequence number
• Every twelve hours, the application retrieves new
  readings from the flash and sends them to the
  gateway
• Five Operations
• Sampe its four sensors
• Log the record to flash

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Motivation Example Pseudocode for hand-tuned
implementation without ICEM
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TelosB
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Five Operations

• Humidity and Temperature are digital sensors
• Total Solar and Photo Active are analog sensors
• The OS can concurrently sample one digital and
  one analog sensor
• The OS must arbitrate sensors of the same kind

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ICEM Drivers Resource Arbitration

• Virtualized
• Simplest for a client to use
• Virtualized drivers buffer client requests
• Provide implicit concurrency
• Usually buffer functional requests (e.g. send a
  packet)
• Dedicated
• Support a single user
• Shared
• Provide explicit concurrency
• Support multiple users, but users must contend
  for the driver through a lock
• Usually buffer lock requests

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ICME Drivers - Virtualized

• Oval Client
• Example
• Data Link Packet Sender
• Round Robin policy
• Application-level millisecond timers
• Application-level millisecond timers
• Maintain per-client state
• Schedule underlying hardware timer

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Virtualized Example

• ADC (Analog-Digital-Converter)
• A shared resource usually multiplexed between
  several clients
• AdcReadClientC.nc, AdcReadNowClientC.nc and
  AdcReadStreamClientC.nc provide virtualized
  access to the HIL
• AdcReadClientC.nc tos/chips/msp430/adc12/AdcReadC
  lientC.nc

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ICME Drivers - Dedicated

• Low-level hardware resources
• Examples
• GPIO Pins

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ICME Drivers - Shared
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CC2420 Stack
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Arbiters

• Lock Resource in T2
• Arbiter Configure ResourceConfigure
• DefaultOwner ResourceDefaultOwner

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Atmegal 128 ADC
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MTS300 Sensor Boards