Smart sensor architecture 2006

Smart Sensor Architecture
Smart Sensor System Architecture in Mimosa
project
Iiro Jantunen / Nokia Research Center
Tutorial Ambient Intelligence,
Toulouse, March 10, 2006

1

© 2006 Nokia

S mart S ens or Architecture.ppt / 2006-03-10 / IJ

Contents
•What is a smart sensor system?
• Transducer, analog electronics, ADC , digital electronics

•O pen architecture for smart sensors
• BluLite
• Public S S I protocol
• nanoUDP/nanoIP networking
• O pen API:s for developing applications for using smart sensors

•Mimosa architecture for smart sensors
• Wired & wireless BluLite or R F ID connection
• Many sensors in many devices over many radio technologies

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© 2006 Nokia


From sensors to smart sensors
Passive sensor (photodiode)

S ensor

Active sensor (S T 3-axis accelerometer)
Wireless smart sensor
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© 2006 Nokia


Smart Sensor Systems
• C ombine functions of sensors and
interfaces
• S ensing
• Amplification
• S ignal conditioning
• AD conversion
• Bus interfacing

• Include higher level functions
• S elf-testing
• Auto-calibration
• Data processing and evaluation
• C ontext awareness
• C ommunications

• Modularity and/or integration
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© 2006 Nokia


• Transducer
• physical reality → electrical
measurable

• Amplifier & filtering
• sensor impedance, signal strength
and quality

• Analog-digital conversion
• Microcontroller / DS P / AS IC
• Digital signal processing
• C ommunications to outside world

• Networking
• S erial interface (US B, S PI, MMC )
• R adio interface (optional)

Transducer
• C onverts between physical
properties

Measurement

Typical/common
techniques

• The resulting property can be

Acceleration

Piezoelectric, capacitive

Displacement, position,
proximity

R eluctance,
optoelectronic, ultrasonic,
radar

• Voltage

F low

Pressure difference

• O ptical power

F orce

Piezoresistive

• E lectrical measurand needs an
amplifier/filtering circuit to provide
electrical power, impedance etc.

Humidity

R esistive, capacitive

Location

G PS

Time

C lock signal

• O ptical measurand needs a
optoelectrical transducer with the
same properties

S ound, pressure

C apacitive

R adiation

O ptoelectronic

G as concentration

Tuned laser &
optoelectronic

• E lectrical capacitance
• C urrent

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© 2006 Nokia


Non-ideal behavior of sensors
C haracteristic

S ensor Design

Nonlinearity

C onsistent

R educe

Drift

Minimize

C ompensate

O ffset

S ensor Interface

C alibrate

Time dependence of offset

Minimize

C alibrate/reduce
Auto-zero

Time dependence of sensitivity
Nonrepeatability

MC U/DS P

Auto-range
R educe

C ross-sensitivity to temp and strain

C alibrate

Hysteresis

Predictable

Low resolution

Increase

Amplify

Low sensibility

Increase

S tore value and correct

Amplify

Unsuitable output impedance

Buffer

S elf-heating

Increase cooling

Unsuitable frequency response

Modify

R educe power use
F ilter

Temperature dependence of offset


Temp. dependence of sensitivity


F rom R . F rank: Understanding S mart S ensors, 2n ed.,
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© 2006 Nokia


Amplifying and analog filtering of sensor output
• Amplifier provides signal strength and
sensor impedance

Issues:

• F iltering needed to suppress noise

• S ignal transmission

• If needed, quite complex functions
can be done with analog electronics,
but many functions are better done in
digital electronics

• Data display

• S ignal conditioning

• O perating life
• C alibration

• easier

• Impedance of sensor and system

• cheaper

• S upply voltage

• need less room

• F requency response
• F iltering

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© 2006 Nokia


Analog-digital conversion (ADC)
• The measurement must usually be
changed to digital form for
• further processing and calculations
• storing to memory
• sending the data
• or just an economical reason

• ADC often included in MC U:s, e.g.
MS P430F 1xx
• Is the resolution (8 or 12-bit) enough?

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© 2006 Nokia


Issues:
• S ample rate
• R esolution (8, 12, 16-bit)
• Accuracy
• Power consumption
• Price

Digital signal processing
• More complex signal processing
• summing many sensors (e.g. 3-axis
accelerometers)
• pattern recognition, e.g. step
counters, speech recognition

• C an be done in

Issues:
• F ixed-point vs. floating-point DS P
• Data precision
• S peed
• Power usage

• AS IC , for cheap mass-production

• Price

• DS P, for high-speed number
crunching

• Internal ADC

• MC U (microcontroller), medium level
calculations, control software

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© 2006 Nokia


• Need for flexible programming: MC U
vs. DS P
• Programming languages: Assembly
vs. C /C ++ or J ava

Microcontroller
• S oftware controlling a smart sensor
system, e.g.
• measurements
• communications
• data memory
• real time clock
• Usually includes
• ADC (DAC )
• timers
• serial ports (S PI, I2C , UAR T)
• flash memory
• Power-efficient, cheap, flexible
• Also called MC U or µC

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© 2006 Nokia


MS P430F169 by Texas Instruments
• Low supply-voltage 1.8 - 3.6 V
• Ultra-low power consumption:
• Active: 330 µA at 1 MHz, 2.2 V
• S tandby: 1.1 µA
• O ff (R AM retention): 0.2 µA
• Wake-up from standby in less than 6 µs
• 16-Bit R IS C , 125-ns instruction cycle
• Program memory 60 kB (flash), R AM 2048 B
• 8-channel 12-Bit ADC with internal reference,
sample-and-hold and autoscan
• Dual channel 12-Bit DAC with synchronization
• 16-Bit Timer_ A & Timer_ B with 3/7 C C R
• O n-chip comparator
• 2 serial interfaces: UAR T or S PI or I2C ™
• S upply voltage supervisor/monitor
• Brownout detector
• Bootstrap loader
• S erial onboard programming

Networking sensors over radio

RF ID

Internet
WL AN

L ow E nd
Bluetooth
UWB

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© 2006 Nokia


C ellular
GPRS/3G
network

BluLite (or Bluetooth Low End Extension)
• Low E nd E xtension for Bluetooth is designed
• to complement Bluetooth by creating a wireless solution that
• allows small devices that are limited in battery power, size, weight and cost to have a wireless
connection with mobile terminals
• without adding yet another radio to mobile terminals (as Z igBee)

• O ptimized for irregular data exchange between Bluetooth enabled mobile terminals and
button cell batter powered small devices
• C oncept assumes two device classes
• Dual-mode (Bluetooth 1.2 with Low E nd mode) for terminals
• S tand-alone (Low E nd mode alone) for sensors and enhancements

Dual-mode device (i.e. terminal)
E
/(BB)
C
ommon LE MAC
C
ommon
Host
Bluetooth
RF
IF
BB/MAC

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© 2006 Nokia


Stand-alone device
(e.g. 3D accelometer node)
S
ensor
AS
IC

LE
E
AS
IC

Stand-alone device
(e.g. fitness gadget)
S
ensor
AS
IC

LE
E
AS
IC

BluLite radio
Channels of the
proposed system

2401

2400

IEEE 802.11b channel
in North America and Europe

2402

2403

Bluetooth channels

2480

2481

2482

2483

MHz

Low End Extension channels

2403

2406

2433

2436

2463

2466

2478

2481 MHz

One default initialization channel, non-overlapping with Bluetooth
T secondary initialization channels, for jamming resistance
wo
24 Unicast channels for user data
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© 2006 Nokia


BluLite radio parameters with 1 Mbps
•Physical bit rate 1 Mbps
•F requency band 2.4 G Hz (IS M band)
•Duplex TDD
•C o-existence of multiple devices
• C onnection setup channel C S MA
• Data delivery F DMA

•J amming avoidance F DMA
•PDU payload
• Byte aligned, variable length, max 255 bytes

•Bit rate excluding PHY and MAC overheads
• Uni-directional with AR Q , max 890 kbps
• Bi-directional with AR Q , max 2 x 471 kbps
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© 2006 Nokia


Basic functions of BluLite radio
ADVERTISE
OFF

IDLE

SCAN

CONNECTED

CONNECT
1.

2.
3.
4.

15

ADVE RTIS E : Makes the local device visible and connectable to all remote devices
within reach. Low-power protocols optimized for this state. A possibility for an
application dependent trade-off between connection set-up delay and the power
consumption.
S C AN: R eturns the addresses and short description of the advertising remote devises
within reach.
C ONNE C T: E stablishes a point-to-point connection with an advertising remote device.
C ONNE C TE D: Provides point-to-point bi-directional data delivery with error detection,
AR Q , segmentation, role switch and a low-activity mode. An evolution path to point-tomultipoint, requiring additions only in master capable devices.

© 2006 Nokia


Mimosa Architecture
Radio sensor node

Back-end server

RFID Sensor
MSP430

4. LEE ASIC

SSI server

Sensors

nanoIP

Internet

FPGA
Digital sensor
management
(memory map)

D
M-SPI UART SPI/IIC
A

BT LEE

RFID (front end)

UMTS
G PR S

M-SPI

1.

3.

1. Host (N6630)
Application
space
M-API

SSI

SSI

(Client)

5. RF-module

1.

(virtual
Server)

4. LOCOS

2. SEMBO
MSP430

Communication
Layer (U-ULIF)

SSI server

Symbian

MCU

SPI

ADC

Device drivers

CART

FPGA

UART SPI/IIC D

A

DAC

Radio BBs

POP
SPI
3. Sensor-HW

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© 2006 Nokia

Device drivers

ULIF


2. Sensor-HW

Simple Sensor Interface (SSI) protocol
• A simple protocol for reading smart
sensors over, e.g., BT LE E
• Also provided for R F ID sensor tags
• Memory map of sensor data on
• C ompatible with IS O 18000-4

• S upport for multiple sensors on
multiple devices
• S upport for data polling or streaming
• Developed in co-operation with
S uunto, Vaisala, Mermit, C E A-LE TI,
O ulu University and Ionific
• Development of the specification
keeps backward compatibility (v0.4-)
• F or specifications, source code and
discussion forum, visit
http://ssi-protocol.net
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© 2006 Nokia


• C lient-server architecture
• Terminal has client software
• S ensor unit has server software

• C lient can
• poll sensors
• ask the server (O bserver) to stream
data to client (Listener)
• read and modify the configuration of
the server

• C ommands have two forms
• C apital letter (“N”), no checksum
• Low case (“n”), the payload has a
C R C checksum

SSI v1.0 command base
C ommand

Dir.

Description

Q /q

0x51 / 0x71

→

Q uery

A /a

0x41 / 0x61

←

Q uery reply

C /c

0x43 / 0x63

→

Discover sensors

N /n

0x4E / 0x6E

←

Discovery reply

Z /z

0x5A / 0x7A

→

R eset S S I device

G /g

0x47 / 0x67

→

G et configuration data for a sensor

X /x

0x58 / 0x78

←

C onfiguration data response

S /s

0x53 / 0x73

→

S et configuration data for a sensor

R /r

0x52 / 0x72

→

R equest sensor data

V /v

0x56 / 0x76

←

S ensor data response

D /d

0x44 / 0x64

←

S ensor data response with one byte status field

O /o

0x4F / 0x6F

→

C reate sensor observer

Y /y

0x59 / 0x79

←

S ensor observer created

K /k

0x4B / 0x6B

→

Delete sensor observer

L /l

0x4C / 0x6C

←

R equest sensor listener

J /j

0x4A / 0x6A

→

S ensor listener created

E rror

E /e

0x45 / 0x65

⇮

E rror messages

F ree data

F /f

0x46 / 0x66

⇮

F ree data for custom purposes

S ensor discovery

C onfiguration

Read data

S treaming data

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© 2006 Nokia


Example SSI command: Discovery reply
• S ensor device answers to Discovery
command sent by a mobile terminal

C

• Discovery R eply message contains
information about one or more sensors.

N (sensor info )

Client

Server

N (sensor info )
Terminal

• The device answers with its address,
command name (N or n) and sensor data

Sensor unit
. . .

• E ach sensor is identified with
• The reply can carry either one sensor per
N command or many depending on buffer
size

• S ensor Id – 2bytes
• Description – 16 byte AS C II
• Unit – 8 byte AS C II

• UAR T or nanoIP frame provides the
information about the length of a single
message

• Type – 1 byte
• S caler - signed 1 byte
• Min – minimum sensor reading value
• Max – maximum sensor reading value

1
Addr

19

1
N/n

© 2006 Nokia

2
Sensor Id 1

16
Sensor desc.


8
Unit

1

1

Type

Scaler

4

4

MIn

Max

. . .

nanoIP networking
• An open-source networking architecture
• Minimal overheads
• Wireless networking

SSI

• Local addressing

• NanoIP makes use of the MAC address of
underlying network technology rather than IP
addresses
• Used with nanoUDP (User Datagram Protocol) or
nanoTC P (Transmission C ontrol Protocol)
• nanoUDP does not provide reliability or ordering
• nanoTC P provides retransmissions and flow control

• Mimosa uses nanoUDP
• http://www.cwc.oulu.fi/nanoip/

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© 2006 Nokia


nanoUDP
nanoIP
ULIF (BluLite
MAC )

Open source SSI/nanoIP implementation
• S S I v0.4 over nanoUDP/nanoIP
provided by O ulu University

• 1 byte protocol type (nanoIP)
• 4 bytes nanoUDP header

• S S I v1.0 (nanoUDP/nanoIP) being
finalized by Nokia R esearch C enter,
will be open source
• Works over BluLite (Bluetooth LE E )

• 2 byte payload + C R C length
• 1 byte S ource port (40 for S S I)
• 1 byte Destination port (40 for S S I)

• n bytes
• S S I payload

• 2 bytes
• optional C R C checksum

1

1

1

1

Prtcol

21

1
LenH

LenL

Source

Dest.

© 2006 Nokia


n
Payload

2
CRC

Mimosa API’s for 3rd parties

Back-end server

IP

Local MIMO S A
S W Applications
UI_ API

C ontext_ API

J ava & C ++
implementation

MIMO S A Ambient
User Interface Layer
MIMO S A C ontext
Awareness Layer

S ensor_ API

MIMO S A
S ensor Layer

LC _ API

MIMO S A
Local C onnectivity Layer

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© 2006 Nokia


Sensor Management Board
• C ontrols the sensors (host)
• C ontrols the sensors and
BTLE E (S ensor R adio Node)
• R eal time clock (with its own
battery)
• C onnectors for
• LO C O S and/or C AR T
• S ensor board (UAR T, S PI/I2C ,
general digital I/O , 8-channel
analog)
• J TAG programming interface
• Debugging ports (UAR T)
• IR Q ports

• MC U runs S S I/nanoIP and
device drivers for sensors

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© 2006 Nokia


Sensor Management Board

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© 2006 Nokia


3.3 V POWER

UART
32.768 kHz clock

UART
I2C
SPI

ADC
DAC

32.768 kHz
crystal

IRQs

USART0

I2C
MCU
text
MSP430F169

JTAG

M-SPI

LOCOS
and / or
CART

UART
8 MHz
crystal

CART

USART1
External
power

• LO C O S and/or C AR T
• S ensor board (UAR T, S PI/I2C ,
general digital I/O , 8-channel
analog)
• J TAG programming interface
• Debugging ports (UAR T)
• IR Q ports

• MC U runs S S I/nanoIP and
device drivers for sensors

SEMBO

Debugging:
SPI0 +
UART1

• C ontrols the sensors (host)
• C ontrols the sensors and
BTLE E (S ensor R adio Node)
• R eal time clock (with its own
battery)
• C onnectors for

32.768 kHz
crystal
3.3 V POWER
3V
BAT

ANALOG

Real time
clock
DS1305E

SEPPO /
SENSOR
BOARD

Mimosa terminal
• Nokia 6630 phone as terminal
• Attached electronics (C AR T, LO C O S ,
S E MBO , R F ) provide the Mimosa
hardware functionality
• J ava software on N6630 will provide the
user interface, context awareness, sensor
management etc.
• LO C O S board as motherboard of
attached electronics
• S E MBO provides local sensor control
• S E PPO (or other) sensor board
connected to S E MBO with a standard
interface
• R F part controlled with F PG A on LO C O S
on baseband-module
• S eparate R F module
25

© 2006 Nokia


RF-module

LOCOS

SEMBO
MSP430
ADC

SSI server

DAC

CART
Device drivers

MCU

SPI

UART

SPI/IIC

FPGA
D
A

Radio BBs

SPI
Sensor-HW

Sensor Radio Node
• S mart sensor which can be read over
BT LE E connection
• E MMI board provides Bluetooth LE E
for communications with mobile
terminals
• S E MBO for controlling BT LE E ,
running the S S I server and sensor
drivers

LEE ASIC

SEMBO
MSP430

EMMI
SSI server
Device drivers

FPGA
M-SPI

UART

SPI

BT LEE

• LO C O S acts as motherboard
• S E PPO (or other) as sensor hardware
board via standard connector
• UAR T
• S PI / I2C
• 8 analog channels
• 15 unspecified digital I/O pins
27

© 2006 Nokia


M-SPI
Sensor-HW

LOCOS

D
A

Sensors demonstrated on Mimosa platform
S ensor

Provider

Notes

Humidity,
temperature,
pressure

Digital

Nokia, (S ensirion,
Intersema)

Weather station,
S S I demonstration

F at %

Amplified
analog

Nokia

F itness & health

EC G

Amplified
analog

C ardiplus

F itness & health,
streaming data over
S S I/nanoIP/BluLite

Lactate,
glucose

Amplified
analog

F raunhofer-IS IT,
C ardiplus, Åmic

F itness & health

G yroscope

29

Interface

I2C

F raunhofer-IS IT, C E ALE TI, S TMicroelectronics

© 2006 Nokia


Weather station
• Demonstration of S S I use
• Weather information: Temperature,
Humidity / dew point, and Pressure
• Intersema MS 5534A pressure sensor
• Pressure range 300-1100 mbar
• Internal 15 Bit ADC
• 6 coeff. software compensation on-chip
• 3-wire serial interface
• 1 system clock line (32.768 kHz)
• 35 ms measurement time

• S ensirion S HT11 humidity sensor

30

© 2006 Nokia


Weather station
• Demonstration of S S I use
• Weather information: Temperature,
Humidity / dew point, and Pressure
• Intersema MS 5534A pressure sensor
• S ensirion S HT11 humidity sensor
• Internal 14-bit ADC
• F ully calibrated
• Internal power regulation
• R ange
• Humidity 0 – 100 %
• Temperature -40 – 128°C

• 2-wire serial interface (not I2C )
• 11/55/210 ms for a 8/12/14bit
measurement.
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© 2006 Nokia


Fat percentage
• Actually measures body water content
(TBW)

• Amplified analog output
• Low-noise O PA2350 two-channel

• Also used for 2-point measurement of
surface impedance, G alvanic S kin
R esponse (G S R )
• S kin stratum corneum humidity
• S tress measurement

32

© 2006 Nokia


C50KHZ
V_FAT

ADC

• 4-point measurement of impedance
with 50 kHz signal

+3.3V

SEMBO
INTERFACE

• F rom TBW, fat-% and dehydration
(∆TBW) calculated

FAT_CS

I_FAT
REF_FAT
GND

ANALOG INTERFACE ELECTRONICS

SIGNAL IN

M1

M2

SIGNAL OUT

E1

E2

E3

E4

Lactate & glucose sensors
• F raunhofer-Institut für
S iziliziumtechnologie (Itzehoe,
G ermany) makes the sensor
• Åmic (Uppsala, S weden) makes a
needle array to penetrate outer layer
of skin
• Measures the lactate or glucose
content of interstitial fluid
• Lactate and glucose sensors differ
only on the enzyme used
• Amplified analog connection to
S E MBO

33

© 2006 Nokia


RFID sensor tag
•V irtual server on the terminal device answers to the S ensor
API when connecting to R F ID sensors
•V irtual server translates the commands to the R F ID reader to
read a specified memory area of the tag
•0x53 (for AS C II “S ”) in address 0x0C (Tag memory layout)
defines the memory layout to be S S I compliant
•Memory mapping designed for one or more sensors per tag
•Memory layout designed to be convenient for S S I use
Bytes

Field

8

0x00 – 0x07

Tag ID

4

0x08 – 0x09

Tag manufacturer

0x0A – 0x0B

Tag hardware type

0x0C – 0x11

Tag memory layout. This defines tag to be S S I compliant sensor.

0x12 –

User data (layout defined by S S I).

6

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© 2006 Nokia


RFID memory mapping: Sensor data space
Byte address

Field name

Type

Description

Example

0x12 – 0x15

Sensor value

4 byte HEX

Variable sensor value

0x00000014

0x16

Type

1 b HEX

Describes the type of the Sensor value
(0x00 = float, 0x01 = signed integer…)

0x01

0x17

Multiplier

1 b HEX

0x18

Status

1 b HEX

Sensor status. Bits 0 – 7 indicate if the
sensor values are valid data (bit = 1) or
not yet valid (bit = 0).

0x19

Empty

1b

For future use. Could be, e.g., number of
sensors.

16

0x1A – 0x29

Sensor description

16 b ASCII

Constant sensor description

“Temperature”

8

0x2A – 0x31

Unit

8 b ASCII

Constant unit description.

“C”

0x32 – 0x35

Minimum value

4 b HEX

Minimum value the sensor can provide.

0x00000000

0x36 – 0x39

Maximum value

4 b HEX

Maximum value the sensor can provide.

0x00000064

0x3A

Activate sensor

1b

Bits 0 – 7 will be written by the reader to
request the tag to write the sensor data

0x01

0x3B – 0x3D

Sensor control

3b

Not defined yet. Could be, e.g., time
needed before sensor value is valid.

n bytes

Optional configuration data or 2nd sensor

8

8

4

n

0x3E –

35

© 2006 Nokia


0x00
0x01

Smart sensor architecture 2006

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