NeSSI Wireless Sensor / working March 7, 2001 John Crawford VP, Business Development Crossbow Technology, Inc.
Background / Outline
Crossbow: Five years in the digital sensor subsystem business
New Wireless sensor / actuator architecture
Sensor / Actuator “Node” uses open (Bluetooth) standard
“Smart I/O (SI/O)” devices provide standards-based Plug-and-Play I/F to almost any sensor
Bluetooth Background
Bluetooth: Norse king who brought together all of the warring factions
Backed by Ericsson, Motorola, Microsoft and others
Designed to replace IR port on PCs, etc. with RF approach
Goal: PCs, PDAs, Cell phones, and peripherals municate easily.
Bluetooth Overview
Bluetooth RF Specification
GHz, Frequency hopping spread spectrum
721 kbps data rate
0 dBm (1 mW) nominal 10 meter range
20 dBm (100 mW) nominal 100 meter range
Automatic retransmit until message receipt is verified (avoid lost data)
Various data security levels can be implemented
Bluetooth vs. Other Technologies
Bluetooth
Proprietary
Manufacturers
Ericsson, CSR, Motorola
Proxim; ;
Various
Frequency
49MHz, 900 MHz,
Modulation
FHSS, 1600/sec
DSSS
FM;FH;DS
Datarate
720kb/sec
11Mb/sec
288kb/sec
Range
10m/100m
100m
Various
Robustness
Very secure
Secure
Various
Power
1mw/100mw
??
Various
Basic Wireless Operation
Inquiry – returns Bluetooth addresses of all devices within range
Establish synchronized link—master/slave
Establish a – up to 7 slave devices in munication
Establish a larger or work
Unlimited additional slave devices “parked”
Master switches from -
Hopping 1500/sec => effective latency O/M milliseconds (10s of milliseconds for works)
Crossbow Node Architecture
300’ or 30’ Range
ARM7
uP
A/D
16 bit
Mux
SENSOR/ACTUATOR
SENSOR/ACTUATOR
SENSOR/ACTUATOR
SENSOR/ACTUATOR
Bluetooth
Radio
Chip
Baseband Controller
SRAM
for
Data
SIO
m
Flash
RAM
SIO
+ Supply
Power
5V
DC
Temp Sensor
AA
B
a
t
t
e
r
y
DC-DC + & 5V
Vo
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