a Cubic-Millimeter Computer

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2 Νοε 2013 (πριν από 3 χρόνια και 7 μήνες)

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Smart Dust: Communicating with
a Cubic
-
Millimeter Computer

Presentation by

Hörður Mar Tómasson

13. October 2006

The Smart Dust project


Went on at UC Berkeley 1998
-
2001


Primary investigator: Kristofer S.J. Pister

The goal


1 mm
³ motes


with onboard sensors,


CPUs


and wireless communications facilities


forming the basis of a sensor network

Fundamental goal


To explore the limitations of
microfabrication technology

Ideas for uses for smart dust


Surveillance networks for defense


Monitoring environmental conditions


Human
-
computer interfaces


Inventory and product quality control


Tracking movements of animals

Power considerations


Batteries: 1 J/mm
³

storage


Capacitors: 10 mJ/mm
³

usable storage


Solar cells: 1 J/(mm
² ∙ day) in sunlight or


1
-
10 mJ
/(mm
² ∙ day) indoors


Optical receiver: 0.1 nJ/bit


Optical transmitter: 1 nJ/bit


A/D converter: 1 nJ/sample


Computation: 1 pJ/instruction

Power considerations


1000 8
-
bit operations per sample will not
make a big difference in power used.


1 mJ per day from a solar cell indoors will
be sufficient for making a measurement
every second, processing the result and
transmitting it.

Low
-
energy computation


Smaller transistors with less parasitic capacitance
consume less dynamic power.


Reduced supply voltage also means less dynamic
power.


Leakage currents can be decreased by reverse
biasing the channel
-
to
-
source junction.


Clock rates of 1
-
100 kHz are sufficient for
working with some important types of physical
signals.

Wireless communication


Radio communication currently requires
several mW of power and preferably
antennas longer than a millimeter.


Semiconductor lasers and diode receivers
can use less power and are more directional.


The Smart Dust project explored optical
communication.

Passive reflective systems


A MEMS corner cube reflector (CCR) with
a side that can be tilted


Less than 1 nJ used per transition


The mote can use the CCR to communicate
with a base station equipped with a light
source.

Active steered laser systems


Semiconductor laser


Collimating lens


MEMS steerable
micromirror

Optical receiver


An imaging receiver has several benefits.


Only one pixel receives the signal but the
ambient light is divided between the pixels.


Several signals can be received in parallel.


The authors did an experiment with a laser
and a video camera.


A smart pixel has an integrated receiver.

Ad hoc mote networks


If the motes can communicate directly with
each other, they can form ad hoc multihop
networks to carry the data around.


This is an interesting problem for network
algorithm design.

An Ultra
-
Low Energy
Microcontroller for Smart Dust
Wireless Sensor Networks

Presentation by

Hörður Mar Tómasson

13. October 2006

Creators of the microcontroller


Brett A. Warneke


Kristofer S.J. Pister

Application


The microcontroller
was developed for this
prototype smart dust
mote.

Architectural features


Highly independent subsystems


Component
-
level clock gating in decoder


Processor halt mode


Guarded ALU inputs


Multiple busses


Harvard architecture


Load
-
store RISC

Main oscillator


Runs continuously at a few kHz


Operates real time clock and five timers


One timer for each sensor sampling period


One timer for invoking the transmitter


One timer for invoking the receiver


One timer for waking up the datapath

Other oscillators


100 kHz for driving the sensor ADC


8 MHz for sampling a 1 Mb/s optical signal

ADC automation


The ADC is configurable to different levels
of automation.


At the minimum level, the sensor and
sample and hold are activated.


At the maximum level, the voltage is
compared to a threshold and, if the
threshold is exceeded, converted and stored
in the SRAM along with a time stamp.

Transmitter


The processor core uses two registers to
specify what memory blocks contain data to
be transmitted.


The transmitter formats the data into
packets and transmits them asynchronously
to the CCR.

Four types of received packets


Short sync packets trigger the transmitter.


Immidiate packets contain an instruction
that is immediately executed.


Program packets are streamed to the
program memory.


Data packets are streamed to the data
memory.

Trimmable oscillator

Specifications

RF Telemetry System for an
Implantable Bio
-
MEMS Sensor

Presentation by

Hörður Mar Tómasson

13. October 2006

The long range goal


NASA wants to develop implantable
sensors to monitor physiological parameters
of humans during space flights.


It would be of great benefit to have
contactless powering and data readout for
the implants.

Advantages of contactless powering
and telemetry


The inductor/antenna is small in size.


There is no need to implant batteries.


The circuit only operates when interrogated,
avoiding heating of the surrounding tissue
and extending the life span of the sensor.


Feed
-
through wires not needed, enhancing
mobility and reducing risk of infection.

This paper


A system for contactless powering and RF
telemetry from an implantable bio
-
MEMS
sensor.


A square spiral inductor/antenna


A MEMS capacitive pressure sensor


A pick
-
up antenna

Spiral inductor/antenna

MEMS pressure sensor

Pick
-
up system


A printed circuit with mounted components


Spiral inductor/antenna, printed


MMIC low noise amplifier, mounted on


Antenna matching network, mounted
discrete components,
Π
-
network


Output connector

Operating principle


The idea is to send pulses down into the
implant and detect the decaying sine
response.

Parameters


Desired frequency range: 200
-

700 MHz


Expected capacitance of pressure sensor:
0.3
-

4 pF


Expected required parameters for square
inductor: 150 nH and Q=10


Several inductors with different geometries
were tried.

Fabrication of the inductor


High resistance silicon wafer


Spin
-
on glass coating


Chrome/gold metallization


The goal is to have high Q.

The next step


Exploring coupling between the inductor
and the pick
-
up antenna through stratified
media