SMART SENSORS

1
SMART SENSORS

• IEEE 1451.3
• Ramesh V.Kandalam
• Dr.John Schmalzel
• ECE Dept, Rowan University, 2005.

2
Outline

• Introduction
• IEEE 1451 family
• 1451.3 Overview
• Objectives of 1451.3
• 1451.3 General Model
• 1451.3 Terms
• Data Types
• Smart Transducer Functional Specification
• Addresses
• Operating States
• Data Sets, Messages and Packets
• Triggering Methods
• TransducerChannel Type Descriptions
• Commands
• Initialization Commands
• Operational Commands
• Query-TEDS Commands
• Read-TEDS Block Commands
• Write-TEDS Block Commands

3
Introduction

• Low-cost, networked smart sensors are developed
  for diverse industrys needs.
• Interfacing the smart sensors to all of these
  control networks and supporting the wide variety
  of protocols require very significant efforts.
• A universally accepted transducer interface
  standard, the IEEE P1451 standard, is developed.

4
What is IEEE1451

• IEEE 1451 is a family of proposed standards for
  "A Smart Transducer Interface for Sensors and
  Actuators". Together these standards provide a
  single generic interface between a transducer and
  external network,independent of the network
  protocol in use.
• The goal is to separate the design of the sensors
  and actuators from that of the networking
  controller, and to make the network protocol
  transparent to the transducer.

5
IEEE 1451 Family
6
1451.3 Overview

• Proposes a standard digital interface (TBIM)
  which can connect multiple physically separated
  transducers in a multidrop configuration
• Digital Communication and Transducer Electronic
  Data Sheet (TEDS) Formats for Distributed
  Multidrop Systems
• Used in applications where transducers are
  distributed across an area in which it is not
  feasible to install an NCAP for each transducer
  channel

7
Objectives

• Enable plug and play at the transducer level with
  Common Communication interface for transducers
  which are physically separated
• Enable and simplify the creation of groups of
  networked smart transducers
• Facilitate the support of multiple networks

8
IEEE 1451.2
http//www.sensorsportal.com/HTML/standard_3.htm
9
1451.3 Implementation
http//www.sensorsportal.com/HTML/standard_3.htm
10
1451.3 partition of general model
http//www.sensorsportal.com/HTML/standard_3.htm
11
1451.3 Terms

• Transducer Bus Controller (TBC) One on each NCAP
  to communicate with multiple TBIMs. Supports
  multiple, time-synchronized data channels to
  occupy single transmission medium (bus).
• A TBC is the hardware and software in the Network
  Capable Application processor(NCAP) or host
  processor that provides the interface to the
  transducer bus.
• The transducer bus provides the communications
  path between an NCAP or host processor and one or
  more TBIMs.

12
1451.3 Terms

• Transducer Bus Interface Module (TBIM) A
  transducer node, like the STIM, but communicates
  with NCAP through multi-drop transducer bus and
  TBC.
• A TBIM is a module that contains the bus
  interface, signal conditioning, Analog-to-Digital
  and/or Digital-to-Analog conversion and in many
  cases the transducer.
• A TBIM can range in complexity from a single
  sensor or actuator to units containing many
  transducers.

13
DATA TYPES

• All data types used throughout the remainder of
  this standard are defined in subordinate
• subclauses.
• Unsigned octet integer for counting(Symbol -
  U8C)
• This data type represents positive counting
  integers from 0 - 255.
• Unsigned octet integer for enumeration(Symbol -
  U8E)
• All 1-octet enumerations are unsigned
  integers, with a value between 0-255.
• Unsigned 16-bit integer for counting(Symbol -
  U16C)
• This data type is used to represent positive
  counting integers from 0-65535
• Unsigned 16-bit integer for field length(Symbol
  - U16L)
• Used to represent unsigned integers from
  0-65535. When used to specify the length of a
  data block, the length field shall not include
  the length of the length field itself.

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DATA TYPES

• Signed 32-bit integer(Symbol - S32)
• Used to represent a signed integer from -2
  147 483 648 to 2 147 483 647
• Unsigned 32-bit integer for counting(Symbol -
  U32C)
• Used to represent a positive counting
  integer from 0 to 4 294 967 295
• Unsigned 32-bit integer for field
  length(Symbol - U32L)
• Used to represent unsigned integers from 0
  to 4 294 967 295. When used to
• specify the length of a data block,
  the length field shall not include the length of
  
• the length field itself.
• Universal Unique Identification(Symbol - UUID)
• UUID is an identification field associated
  with the TBIM whose value is unique.
• There shall be no requirement that the
  interpretation of the UUID reflect the
• actual place or time of the manufacture
  of TBIM. The use of time and location in
• the algorithm shall be used only to
  ensure uniqueness.

15
Smart Transducer Functional Specification
16
Addresses

• Sixteen-bit addresses are used on the transducer
  bus.
• Concatenating the TBIM and the TransducerChannel
  number forms the 16-bit address.
• The TBIM is assigned by the system as part of the
  discovery process and forms the eight most
  significant bits of the address.

17
Addresses
Classes of Addresses
? The commands addressed to the Global Address
shall be received and honored by all the
TBIMs on the bus. ? Commands issued to an
AddressGroup shall be honored by all
Transducer Channels that have been initialized as
members of that AddressGroup, irrespective
of the TBIM on which they reside.
18
Addresses

• Commands issued to a TBIM apply to the TBIM as a
  unit.
• Commands issued to a specific TransducerChannel
  apply to that TransducerChannel only
• There are no commands defined that shall be
  honored when addressed to the TBC address.

19
PLUG AND PLAY CAPABILITY
TBIM and TBC that are built must be able to be
connected using a transducer bus and be able to
operate without any changes to the system
software. No need for different drivers,
profiles or other software changes to provide
basic operation of the transducer. Connectors
and bus power supply voltages are recommended by
this standard and not required makes it
necessary for the user to determine if a TBIM or
TBC can be safely connected to a
particular implementation of the transducer bus.
20
Operating States
TransducerChannel Operating States
21
Structures used to store and transmit data

• There are three structures that are used to store
  and transmit data in this standard.
• They are
• The data set,
• The message, and
• The packet.
• Data sets
• All TransducerChannels operate with data sets.
• Three fields within the TransducerChannel TEDS
  define a data set.
• The Maximum data repetitions field
  defines the maximum number of individual data
  samples in a data set.
• The actual number of samples may be made lower
  than the number in the Maximum data repetitions
  field by the optional Set TransducerChannel Data
  Repetition Count command.
• The second field is the Series increment field.
  This field is used to determine the interval
  between samples and it may be overridden by a
  manufacturer-defined command or an embedded
  actuator.
• The third field is the Series units field. This
  field defines the units for the Series increment
  field. The implication of the Series units field
  is that the units of the Series increment field
  does not need to be time and that if this is the
  case the time interval between samples may not be
  uniform.
• EXAMPLEThe Series units are degrees
  Kelvin and the Series increment is 0.5. This
  combination would cause a sensor to acquire data
  every 0.5 degrees. The samples would be at
  uniform temperature intervals instead of uniform
  time intervals.

22
Structures used to store and transmit data

• Messages and packets
• Messages may contain up to 65 520 octets plus 14
  octets in headers.
• The data link and physical layers of the protocol
  stack transmit packets.
• If a message is too long to fit within a single
  packet, it is the responsibility of
• the Data Link Layer in the protocol stack to
  break messages down into
• multiple packets for transmission.

23
Enabling and disabling triggers

• A TransducerChannel may have its ability to be
  triggered enabled or disabled by means of
  commands.
• A trigger is a signal applied to a
  TransducerChannel or set of TransducerChannels to
  cause them to take a particular action.
• Trigger methods
• There are two methods recognized by this standard
  to initiate a trigger.
• Explicit triggers commanded by the TBC and
• Events within a TBIM that may be used as
  triggers.

24
Trigger methods

• Trigger messages
• Trigger messages are sent from the TBC to one or
  more TransducerChannels
• on a transducer bus.
• A trigger message may be addressed to any of the
  following
• A TransducerChannel - applies to one
  TransducerChannel on one TBIM.
• A TransducerChannel Proxy - It is an
  addressable resource within a single TBIM
• that is capable of representing one or
  more TransducerChannels within that TBIM.
• A TBIM - Triggers all TransducerChannels that
  are implemented on that TBIM.

25
Trigger methods

• An AddressGroup - A trigger message issued to
  that AddressGroup triggers all
• members of that AddressGroup.
• The global address - A global trigger applies to
  all TransducerChannels in all
• TBIMs on a given transducer bus. The
  system issues a global trigger by issuing a
  trigger
• message to the global address.
• Events used as triggers
• Events within a TBIM may be used as triggers.
• An event used as a trigger may be formally
  implemented as an Event Sensor.

26
Trigger methodsContinued.

• Nominal trigger logic

Simple TransducerChannel functional blocks
27
Trigger methodsContinued.

• Trigger logic based on event recognition

Event sensor output used as a trigger
28
TransducerChannel type descriptions

• The TransducerChannel types are
• Sensor
• Event sensor
• Actuator
• Sensor
• A sensor shall measure some physical parameter on
  demand and return digital data representing that
  parameter.
• On the receipt of a trigger the sensor shall
  start the collection and storing of a data set
  within the TBIM.
• A sensor, in the operating state, shall respond
  to a read command by returning the appropriate
  data set.

29
TransducerChannel type descriptions

• Event sensor
• An event sensor determines the level of some
  physical phenomena but determines when a change
  of state has occurred.
• The TEDS definition for an event sensor is the
  same as for any other transducer.
• Actuator
• An actuator shall cause a physical or embedded
  output action to occur.
• The actuator output state changes to match the
  appropriate data set when a triggering event
  occurs.

30
Hot-swap capability

• Hot-swap capability exists within the system on
  two levels.
• It shall be possible to disconnect a TBIM from
  the bus or to connect a TBIM to the bus without
  powering down the bus and without damage to
  either the TBIM being inserted or anything else
  connected to the bus.

31
Commands

• Commands are divided into two categories,
• Standard and Manufacturer-defined.
• The most significant octet shall be used to
  define the class of the command.
• The least significant octet, called the function,
  shall identify the specific command within the
  class.
• For example, if the most significant octet
  defines the Read TEDS block
• class of commands, the least significant octet
  then specifies the TEDS to be read.

32
Initialization commands

• The initialization class of commands is used to
  set up a TBIM.
• A TBIM, TransducerChannel or TransducerChannel
  proxy only responds to commands in this class
  when in the halted state.
• Commands in this class that may be issued to both
  a TransducerChannel and a TranducerChannel proxy
• Set TransducerChannel data repetition
  count
• Used to change the number of data samples
  in a data set to a number between one and the
  maximum number found in the maximum data
  repetitions field of the TransducerChannel TEDS.
• If an acknowledgment is required for
  this command, the reply shall contain the 32-bit
  status word for the TBIM in the data field

33
Initialization commandsContinued
Read TransducerChannel data repetition
count Used to read the actual number of
TransducerChannel pre-trigger counts that are
assigned for the addressed TransducerChannel. Rea
d AddressGroup assignment This command is used
to read all of the AddressGroups to which the
addressed TransducerChannel or TBIM is
assigned.
34
Operational commands
Operational Commands

• Operational commands are the class of commands
  that are expected to be used in the collection
  and processing of data.
• Commands in this class may be issued at any time
  after an alias is assigned to the TBIM.
• Query data block
• This command is used to define to the TBC the
  information required to read or write large data
• blocks

35
Operational commandsContinued
Read TransducerChannel data block The reply to a
Read data block command uses the Reply
Protocol The size of the response is limited by
the smaller of either the Maximum block size of
response field in the Read data block or the
maximum size block that the TBIM can
transmit. Write TransducerChannel data
block This command is used to write large data
blocks into a TBIM or TransducerChannel. The
reply to a write data block command shall contain
two octets. These two octets shall represent
a 16-bit number giving the number of octets
received.
36
Query TEDS commands

• This class of commands is used by the TBC to
  solicit information required to read or write the
  TEDS.
• Some TEDS apply to the entire TBIM while others
  to a specific TransducerChannel.
• Query TEDS commands may not be addressed to
  AddressGroups or globally.
• The TBIM is required to provide a reply to all
  Query TEDS commands
• When the Unsupported TEDS attribute is set, the
  TBIM shall return a zero for the Current size of
  the TEDS and the Maximum TEDS size fields.

Query TEDS response in the data field
TEDS attributes
37
Read TEDS block commands

• To read a TEDS, the TBC uses this class of
  commands.
• The function field of the command shall contain
  the TEDS access code,
• There are arguments for this command the maximum
  block size that the bus controller supports, and
  the offset into the TEDS to begin reading.
• The size of the response is limited by the
  smaller of either the Maximum block size of
  response field in the Read TEDS block command or
  the maximum size block that the TBIM can
  transmit.
• The reply to a Read TEDS block command uses the
  Reply Protocol
• The reply to a Read TEDS block command shall
  contain a variable number of octets in the data
  field.

Arguments for a read TEDS block command
Read TEDS block response
38
Write TEDS block commands

• This class of commands is used to write the TEDS
  in a TBIM.
• The Write TEDS block command uses the Command
  Services Protocol. The total number of octets in
  the message (including protocol wrappers) shall
  not exceed the value reported by the TBIM in the
  Maximum block size for Write TEDS block command
  field of the Query TEDS command.
• A Write TEDS block command shall create a new
  TEDS if one does not already exist with that
  function. If the TBIM is not designed to allow
  the TEDS to be created, the Write TEDS block
  command shall not write any data into TEDS memory
  because the TEDS is unsupported.

39
TRANSDUCER ELECTRONIC DATA SHEET(TEDS)
SPECIFICATION

• TEDS are blocks of information that are intended
  to be stored in non-volatile memory with a TBIM.
• When the TEDS are stored in some location than
  TBIM then they are called as Virtual TEDS.
• The manufacturer of the TransducerChannel
  provides the virtual TEDS in some electronic
  form.
• It is users responsibility to link the data
  information that is guaranteed to be available
  from the TBIM, i.e., UUID(Unique Identification
  ID).
• The NCAP or the host processor provides this
  service if it is used.

40
General format for TEDS
TEDS length -- total number of octets in the TEDS
data block plus the two octets in
the checksum. Data block -- This structure
contains the information that is stored in a
specific TEDS. Checksum -- The checksum shall be
the ones complement of the sum (modulo 216) of
all preceding octets, including the initial TEDS
length field and the entire TEDS data block.
41
Meta-TEDS

• The Meta-TEDS is accessed using a
• Query TEDS command,
• Read TEDS block command,
• Write TEDS block command,
• or
• Update TEDS command with a
• destination address of a TBIM.

42
Meta-TEDS

• The Meta-TEDS should be implemented as
  Read-only to prevent an end user from modifying
  its content.

43
TransducerChannel TEDS

• This is a required TEDS.
• The function of the TransducerChannel TEDS shall
  be to make available at the interface all of the
  information concerning the TransducerChannel
  being addressed to enable the proper operation of
  the TransducerChannel.

44
TransducerChannel TEDS
This TEDS is accessed using a Query
TEDS command, Read TEDS block command,
Write TEDS block command, or
Update TEDS command with a destination
address of a TransducerChannel.
45
Calibration TEDS

• The Calibration TEDS is accessed using a
• Query TEDS command,
• Read TEDS block command,
• Write TEDS block command, or
• Update TEDS command
• with a destination address of a
  TransducerChannel.

46
Text-based TEDS

• The function of these TEDS is to provide
  information for display to an operator.
• There are five TEDS that fall into this category.
  
• Meta- Identification TEDS,
• TransducerChannel Identification
• TEDS,
• Calibration-Identification TEDS,
• Commands TEDS
• Location and Title TEDS.

47
Manufacturer-defined TEDS PHY TEDS

• Manufacturer-defined TEDS may be in any format
  required by the manufacturers application
  software.
• For a manufacturer-defined TEDS that are being
  sent to the TBIM, the system shall take the
  information, apply the length field and checksum
  fields and transmit it to the TBIM.
• The PHY TEDS is a required TEDS.
• The function of the PHY TEDS shall be to make
  available at the interface all of the information
  needed to gain access to any channel, plus
  information common to all channels.

48
Things we have seen till now

• Implementation model of IEEE 1451.3
• Terms (TBC and TBIM) in IEEE 1451.3
• Data Types
• Addresses
• Operating States
• Data Sets, Messages and Packets
• Enabling and Disabling the triggers
• Triggering Methods
• TransducerChannel Descriptions
• Commands
• TEDS
• Meta-TEDS
• TransducerChannel TEDS
• Calibration TEDS

49
CONCLUSION

• The Standard has provided the beginning of a
  consistent set of tools to address the issue of
  displaying data in a standardized way.
• By providing a way for a set of base units to be
  incorporated into the transducer, the working
  group has standardized the way that the units are
  represented in the TEDS.
• A transducer that is built and calibrated per the
  standard should be able to plug into any system.

50
REFERENCES

• http//www.completetest.com/IEEE1451_overview.htm
• http//www.sensorsportal.com/HTML/standard_3.htm
• http//www.tarallax.com/ieee1451.html
• www.sensornet.gov/ftbragg/IEEE1451_Sensor_Standard
  _Fort-Bragg.pdf
• www.sensorsportal.com/HTML/DIGEST/july_04/E_05.pdf
  
• www.ieee1451.nist.gov/group3.html
• www.standards.ieee.org/catalog/olis/im.html
• IEEE Standard for a Smart Transducer
  Interface for Sensors and
• ActuatorsDigital Communication and
  Transducer Electronic Data Sheet (TEDS)
• Formats for Distributed Multidrop
  Systems

51
Questions
52
Assignment

• Calculate the time of a sample in a data set.
  Briefly describe and show the formula used in the
  calculation.
• Hint Chapter 5 of IEEE Standard for a Smart
  Transducer Interface for Sensors and
• ActuatorsDigital Communication and
  Transducer Electronic Data Sheet (TEDS)
• Formats for Distributed Multidrop
  Systems