CANbus Solutions and National Instruments

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CANbus SolutionsandNational Instruments
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Agenda

• Automotive test systems
• Introduction to CAN
• CAN basics
• Overview of National Instruments CAN solution
• Typical automotive test applications
• Synchronization capabilities with CAN and DAQ
• Real- time capabilities with CAN and DAQ

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Traditional Test Systems
PC
Sensor-Based Vehicle
DAQ
Signal Conditioning
Point to Point wiring
Thick cable harness
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CAN-based Test Systems
Need Validate vehicle CAN systems
Single CAN cable
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Introduction to CAN
So, what is CAN?
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CAN Open Industry Standard

• Invented by Bosch in mid-80s
• High-speed CAN ISO 11898
• Low-speed CAN ISO 11519 (fault tolerant CAN)
• Heavily used in automotive
• Physical layer for DeviceNet, CANOpen, SDS

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Huge Market in Automotive

• Well established in German/European automotive
• High growth in U.S./Japanese automotive

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CAN Automotive Applications
Power Steering
Power Windows
Lights
Instrument Panel
ABS
Transmission
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Other CAN Markets
Public Transportation
CAN
Military Systems
Avionics
Farm Machinery
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CAN Basics
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Types of CAN

• High speed CAN (ISO 11898)
• Up to 1 M bits/sec transmission rate
• Low speed CAN (ISO 11519)
• Up to 125 K bits/sec transmission rate
• Fault tolerant

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Benefits of CAN

• Lower cost from reduced wiring Multidrop cable
• Compared to two wire point-to-point wiring
• Highly robust protocol
• Built-in determinism
• Fault tolerant (low-speed CAN)
• Reliable proven in field
• Track history of 10 years in the automotive
  industry

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CAN Physical Layer Specifications

• CAN data (up to 8 data bytes in a frame)
• Maximum 1 Mbit/sec
• 40 Meters at 1 Mbit/sec
• 6 Km at 10 kbit/sec
• Maximum 2032 nodes per bus (theoretical)
• Approximately 100 node practical due to
  transceiver
• About 3-10 nodes are used in practice

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CAN Frame Types

• Data frames - Arbitration ID (11 bit or 29 bit)
• Indicates message priority
• Remote frame
• Error frame
• Overload frame

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CAN Arbitration

• When two devices attempt to transmit
  simultaneously, CAN uses non-destructive bitwise
  arbitration to resolve the collision.

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CAN Data Frame Example
Gearbox CAN Data Frame
0x5
.
Temperature
Pressure
Torque
.
ID
4 bytes
2 bytes
2 bytes
ABS CAN Data Frame
Data 8 bytes
0x10
Temperature
Torque
.
.
ID
4 bytes
2 bytes
Data 8 byte ( 2 bytes not used)
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National Instruments CAN Solution
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National Instruments CAN Hardware

• High speed CAN (ISO 11898)
• PCI, PXI/CompactPCI, PCMCIA, ISA
• 1 and 2 ports
• Max. Baud rate 1mb/s
• Low speed CAN (ISO 11519)
• PCI, PXI/CompactPCI, PCMCIA
• 1 and 2 ports
• Max. Baud rate of 125kb/s
• Dual speed CAN (ISO 11898 ISO 11519)
• PCI, PXI/CompactPCI, PCMCIA
• 2 ports (1 high speed and 1 low speed)

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National Instruments CAN Software

• LabVIEW VI library
• LabWindows/CVI language interface
• C/C language interface
• Bus Monitor utility for easy monitoring and
  logging
• Special CAN bus features
• Support for synchronization with NI-DAQ
• Support for LabVIEW Real-Time under PXI

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NI-CAN access to the CAN bus

• Object oriented architecture
• CAN Network Interface Object - CAN port
• Low level access to CAN bus
• When writing or reading you must specify the ID,
  data length, etc... of interest
• CAN Object - encapsulates a specific arbitration
  ID along with its data
• High level access
• At configuration time, you specify ID, data
  length, etc.. of interest

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NI-CAN Network Interface Object
ID3
ID1
ID2
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NI-CAN CAN Objects
Receive data periodically using remote frame
Transmit data periodically
Transmit periodic waveform
ID1
ID2
ID3
ID1
ID2
ID3
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NI-CAN Architecture (Windows)
Your Application
NI-CAN Driver
RTSI
Shared Memory
CAN Network
CAN Stack
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Automotive Test Applications
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Typical CAN Applications

• CAN device durability testing
• CAN device validation testing
• Examples
• Torture testing of a gear box
• Testing instrument clusters
• Testing an ABS system

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Example Gearbox Test
DAQ-controlling the test stand -Soft
PC
CAN bus
CAN
DAQ
CAN Frames
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Synchronization with CAN DAQ
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Software Synchronization

• Loop/global variable controlled
• Pros
• Easy to implement
• Cons
• Non-deterministic due to software latency
• Measurement data not time-correlated with CAN
  data
• Requires manual correlation for charting or
  analysis

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Hardware Synchronization

• Hardware controlled
• Pros
• Very deterministic because no software timing
• Measurements time-correlated with CAN data
• Simplifies charting and analysis
• Cons
• Requires support from hardware vendor

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RTSI Real Time System Integration

• Timing and Trigger bus used by National
  Instruments
• PXI implemented on PXI trigger bus
• PCI requires RTSI cable
• CAN board configurable as RTSI master or slave
• Synchronize to one or more CAN or DAQ interfaces
• Synchronize to one or more CAN frames

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DAQ as RTSI Master

• Transmit CAN frame on RTSI input from DAQ
• Synchronize to DAQ update clock for transmitting
  single frame or waveform
• Timestamp RTSI trigger on RTSI input from DAQ
• Synchronize to DAQ scan clock for data
  correlation
• CAN read queue collects asynchronous CAN data as
  well as DAQ triggers

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DAQ Masters Synchronization Event
CAN card
RTSI
DAQ card
AI Scan Clock or AO Clock Update
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CAN as RTSI Master

• Output RTSI trigger on receiving a
• CAN frame
• DAQ uses RTSI signal as acquisition clock
• Output RTSI trigger on transmission of
• CAN frame
• similar to analog output from DAQ
• Output RTSI trigger on demand
• manual control via pushbutton

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CAN Masters Synchronization Event
Output RTSI on CAN frame received
Output RTSI on CAN frame transmit
Ack
CAN card
RTSI
DAQ card
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Real- time capabilities with CAN
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NI-CAN and LabVIEW Real-Time

• Applications ECU testing, simulation,
  validation
• Develop on a PC with LabVIEW
• Deploy on a PXI controller with LabVIEW Real-Time
• No modification to your code
• Supports synchronization of CAN and DAQ
• Deterministic timing

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LabVIEW Real-Time CAN Architecture
LabVIEW Front Panel
Download (Ethernet)
Controller Running LabVIEW-RT NI-CAN driver
RTSI (Trigger) Bus on back plane
CAN Interface
DAQ Board
PXI Chassis
Shared Memory
LabVIEW Application
CAN Stack
CAN Network
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Summary

• Open standard used in
• Automotive
• Public Transportation
• Avionics
• Military
• CAN DAQ synchronization a must for validation
• CAN LabVIEW Real-Time deterministic timing

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Useful Information

• LabVIEW Starter Kits on NIs Developer Zone
• Go to Development Library then Industrial
  Networks
• Or click here CAN Starter Kits
• Starter Kit examples
• CAN-DAQ Synchronization
• CANdb for LabVIEW
• SAE J1939