Wireless Sensor Networks (WSN) CPU Group

1
Wireless Sensor Networks (WSN) CPU Group

• Progress Presentation

Almir Davis Yong Zhang
Halligan Hall
03/17/2005
2
Agenda

• Sensor Card Diagram
• Choosing Power Supply
• CPU Design Progress
• CPU New Features
• Questions from the Proposal Presentation
• Current Questions

3
WSN Block Diagram
4
Sensor Card
5
Types of Chemical Weapons

• Nerve Agents
• Nerve agents attack the bodies nervous system.
  Nerve agents causse breathing difficulties,
  convulsions, paralysis, and death. Nerve agents
  can be inhaled or absorbed through the skin.
  Symptoms of nerve agent poisoning include runny
  nose, tightness of chest, difficulty breathing,
  excessive sweating, nausea, vomiting dimness of
  vision, pinpointing of the pupils, convulsion,
  and death.
• Blister Agents
• Blister agents attack the lungs, eyes, and skin.
  They blister both skin and mucous membranes.
• Blood Agents
• Blood agents interfere with the bodies ability to
  absorb oxygen. The victim dies because the body
  tissues are starved of oxygen. Blood agents cause
  headaches, vertigo, and nausea before death.
• Choking Agents
• Choking agents attack the lungs, causing them to
  fill with fluid. Choking agents are detected by
  their smell and their irritancy. The victim
  suffocates by drowning in his own body fluid.
  Choking agents cause coughing, choking, tightness
  of the chest, nasea, headache, and watering of
  the eyes.

6
Common Chemical Weapons
7
Choosing power supplies

• AA Batteries
• Capacity 650mAh 3135mAh
• Button Cells
• Capacity 45mAh 500mAh

8
AA Batteries

• Alkaline AA batteries
• most common AA battery type.
• Pre-charged to 1.5 Volt.
• Unsteady voltage.
• Capacity 2,700 to 3,135 mAh. Most AA Alkaline
  cells offer a capacity of 2,850 mAh. The
  expensive Energizer e2 alkaline offer 3,135 mAh
  and the cheapest cells offer 2,700 mAh, all
  pretty much alike at low drains. (That's why
  Consumer Report's testing suggested to get
  whatever's cheapest).
• Shelf life some current premium brands exceed 6
  years.

9
AA Batteries

• Lithium AA batteries
• Premium AA battery type.
• Pre-charged to 1.5 Volt.
• Constant 1.5 Volt over their life.
• Capacity premium brand Lithium AA cells offer
  around 3,000 mAh, the same as Alkaline.
• Shelf life up to ten years, and a longer lifetime
  than an alkaline battery. Also retain much better
  capacity in low temperature (less than 25 C)
  than alkaline batteries
• Disadvantage expensive compared to Alkaline. 

10
AA Batteries

• Rechargeable AA batteries
• Ni-Cd, Nickel-Cadmium Capacity 650 to 1,000
  mAh
• Ni-MH, Nickel-Metal Hydride Capacity 1,350 to
  2,500 mAh

11
Low Battery Warning Circuit

• What would be required is a circuit that
  constantly monitors the battery voltage, and if
  it reaches a magic low-point, it gives a signal
  to CPU. Then the CPU will command the transceiver
  to send a low battery warning to the base
  station.
• Such a circuit would have to be micro-powered
  that is, it draws next to nothing from the
  battery itself, so it may be left in the circuit
  continuously without adversely affecting battery
  reserve.

12
CPU Block Diagram
13
CPU Features

• Cut-through data path
• Aggregation of Sensors packets
• Selection of Sensors packets
• Sleep cycles, RX Active cycles, TX Active
  cycles
• In-Band Hot reset
• Support for downstream traffic
• CPU configuration registers programmable
  wirelessly
• Operating system instruction set support
• Send to node selection capability
• Receive from node selection capability
• Node ID wireless reprogram option
• Event-Based Queries and Lifetime-Based Queries
  support

14
Transmit Cut-Through Data Path
15
Receive Cut-Through Data Path
16
Aggregation of Sensors packets
17
Selection of Sensors packets
18
CPU Configuration Register Access
19
CPU Register Map
ADDR Function DATA20 Description
000 NODE ID Data signifies the NODE ID (default value selected using jumpers)
001 TX MODE 100 TX Cut-through (default) 001 TX Aggregation 010 Select (parameter A relevant) 111 Select (parameter B relevant)
010 RX DUTY 000 X sec ACTIVE Y sec SLEEP 001 Z sec ACTIVE N sec SLEEP .
011 TX DUTY Same as RX DUTY except it applies to transmitter
100 RECEIVER NID Send packets only to the node specified by these 3 bits (111 reserved for broadcast, 000 default value for base station)
101 BATTERY LIFE RO register (packet aimed for this register will trigger a transmit packet with BATTERY LIFE information
110 Reserved
111 Reserved
20
Duty Cycles

• RX Duty Cycle (For example wake up every 30 s
  for 1 sec)
• TX Duty Cycle
• Sensor TX side and Transmitter TX side can be
  decoupled
• Transmitter might be turned on only if sensor
  detects an important information
• Sensor TX side and Transmitter TX side can be
  turned on at the same time regardless what data
  is being sampled

21
In-Band Hot Reset

• The way to reset the node wirelessly
• HOT 1 signifies the hot reset insertion
• The entire packet after the preamble should be
  all 1s (packet includes only 1 DATA50 word)
• If HOT 1 but the packet has some 0s drop the
  packet - no reset

22
Support for downstream traffic

• Capability to program the node from the base
  station or any other node
• Capability to receive OS instructions and digest
  them
• Node recognition capability
• Send to node selection capability
• Receive from node selection capability

23
Node ID wireless reprogram option

• Node ID is programmed using jumpers (problem
  cannot go into the birds nest to switch jumpers
  values) or using the default factory setting or
  using EPROM (EEPROM) etc
• Solution Wireless ability to reprogram the
  default value

24
Event-Based Queries support

• Event-Based Query is the way to program the node
  to send the data acquired only if the programmed
  parameters are met
• ON EVENT bird-detect (loc)
• SELECT AVG (light), AVG (temp), event.loc
• FROM sensors AS s
• WHERE dist (s.loc, event.loc)
• SAMPLE INTERVAL 2 s for 10 s

25
Lifetime-Based Queries support

• Lifetime-Based Query is the way for user to
  program the query duration in days, weeks or
  months.
• SELECT nodeid, accel
• FROM sensors
• LIFETIME 30 days
• (Note we do not plan to have day/month/year
  precision but rather permanent sampling, no
  sampling, even-based sampling, short-period
  sampling)

26
Questions from the Proposal Presentation (1)

• Internal tri-state buffer use?
• Internal tri-state buffers is not planned to be
  used. We plan to use simple multiplexers instead.
• If receiver is asleep how are you going to get
  the data?
• We will have to make sure that the receiver is
  awake at the right point of time (synchronization
  needed, programmability support provided by our
  CPU)
• How do you distinguish 2 sensors if you use the
  same 3-bit addr for both?
• Sensor ID field is used to distinguish among
  sensors.

27
Questions from the Proposal Presentation (2)

• How do you decide whether to send data or not?
• Configuration registers provide the ability to
  decide the operational mode. They will drive
  decisions when to sample/send data.
• Run the CPU fast, sample quick, power down, go to
  sleep in between samples. Saves Power!
• We will research more on this one. At this point
  we are not sure that with the faster clock we
  will save power.
• Is there a common power source between
  CPU/sensors/transceiver?
• Yes and most likely it will be 2 AA batteries.

28

• ?