CAN and Cotex m3

1. CAN Network Development
Program @IoTShow.in
by
Prof. Nalini C. Iyer
Prof. Venkatesh Mane.
Prof. Vishal Pattenshetty

2.  Introduction to CAN.
 What is CAN and Why CAN ?
 CAN protocol overview
 CAN physical layer
 CAN data link layer
 Cortex-M3 programming
 Project on CAN communication
 Hands-on Exercises on Real World System
 Analysis of CAN data using BUSMASTER and CAN data
base creation

3. What is communication ?
Communication is nothing but exchange of
information or data.
Why there is need for communication in a
vehicle?
To reduce the cost.
To reduce size.
To reduce the complexity.
To improve the performance.

4. What are the different types of communications?
Serial Communication
Parallel Communication
Advantages and Disadvantages of Both

5. Comparison of different protocols

6. • In "multi-drop" communication, one device
communicates with multiple receivers.
Example: RS-422.
• Where in "multi-point" communication,
multiple devices communicates with
multiple receivers. Example: RS-485

7. What is CAN ?
Controller Area Network
It is a serial bus system used to communicate between several embedded 8-bit and
16-bit
It was originally designed for use in the automotive industry but is used today in
many other systems (e.g. home appliances and industrial machines).
It is asynchronous serial transmission protocol.
 Highest Baud Rate is 1Mbit.
 CAN uses a message oriented transmission protocol.
 There are no defined addresses, just defined messages.
 Non-destructive arbitration system by CSMA with collision detection.
 Multi-master / Broadcasting concept
 Sophisticated error detection & handling system

8.  Wired And logic
 CSMA/CD
 Non destructive
 NRZ format
 Bit stuffing
 Fault confinement
 2 wire
 Prioritization of messages

9.  Differential voltage
 Transceivers
 Recessive and dominant bits
 Event triggered protocols
 CAN version 2.0A and 2.0B
 ISO-OSI compliant
 Plug in-Plug out protocol
 Serial asynchronous
 Maximum of 8 bytes in a frame
 automatic retransmission

10. Why CAN ?
 Mature Standard
 CAN protocol more than 16 years
 Numerous CAN products and tools on the market
 Simple Transmission Medium
 Twisted pair of wires is the standard, but also just one
wire will work
 Other links works, too: Opto - or radio links
 Excellent Error Handling
 CRC error detection mechanism
 Fault Confinement
 Built-in feature to prevent faulty node to block system
 Most used protocol in industrial and automotive world

11. CAN Controller
CAN Transceiver

12. CAN Protocol
There 4 types of frames
Data Frame
Remote frame
Overload frame
Error Frame

13. CAN Protocol
DATA Frame
• SOF – Start of Frame
• Identifier – Tells the content of message and priority
• RTR – Remote Transmission Request
• IDE – Identifier extension (distinguishes between CAN standard,11 bit
identifier, and CAN extended, 29 bit identifier.)
• DLC – Data Length Code
• Data – holds up to 8 bytes of data
• CRC – “Cyclic Redundant Check” sum
• ACK – Acknowledge
• EOF – End of Frame
• IFS – Intermission Frame Space. Minimum number of bits separating
consecutive messages.

14. Standard frame and extended frame

15. • Messages are
distinguished by message
identifiers.
• The identifier is unique to
the network and defines
the content & priority of
the message.
CAN Protocol

16. CAN Protocol
• When several messages access
the bus at the same time, the
one with the higher priority
“wins”.
• The identifier with the lowest
binary number has the highest
priority.
• The priority are specified
during system design and
cannot be changed
dynamically.

17. CAN Protocol
• Access conflicts on the bus
are resolved by a “wired
and” mechanism, where the
dominate state overwrites
the recessive state.
• All “losers” automatically
become receivers and they
won’t try to send another
message until the bus
becomes available again.

18. CAN Protocol
• If one or more errors are detected, the transmission is
aborted. This prevents all other stations or nodes from
accepting the message.
• Re-transmission is automatic. If errors continue, then the
station or node may switch itself off to prevent the bus
from being tied up.
• Error detection is done on two levels:
– Message level
– Bit level

19. CAN Protocol
• Message Level
– CRC = Cyclic Redundant Check sum
– Frame Check = compares message to fixed format and frame
size
– ACK errors = if transmitter does not receive an ACK signal
from the receivers
• Bit level
– Monitoring = The transmitter monitors the bus signal as it
sends the message and compares the bit sent to the bit
received.
– Bit Stuffing = After five consecutive equal bits, the
transmitter inserts a stuff bit with a compliment value into
the bit stream. The receivers remove this stuff bit.

20. CAN Protocol
 Error Frame: sent after a violation frame format
 Overload Frame: prevents data overflow from a slower CAN
Overload Frames are not really used

21. TEC and REC counters allows to prevent from faulty nodes
 CAN Node Error States:
 Error Active: Normal state, node can send all frames (error frames
included)
 Error passive: Node can send all frames excluding error frames
 Bus off: Node is isolated from bus
 Internal Counters: TEC & REC
 TEC: Transmit Error Counter
 REC: Receive Error Counter

22. CAN Protocol
Node 1 Node 2 Node 3 Bus
D D D D
D D r D
D r D D
D r r D
r D D D
r D r D
r r D D
r r r r
‘1’ Recessive (r)
‘0’ Dominant (D)
Two logic states on the CAN bus
Bus in dominant state
Wired-AND Function
Bus in recessive state
or idle

23. µController CAN
Controller
CAN
Transceiver
CANBus
CAN_H
CAN_LRXD
TXD
CAN_L
CAN_H

24. CAN Physical Layers
CAN - High - Speed ( ISO 11898 ) :
node 1 node 30
120
Ohm
120
Ohm
CAN_H
CAN_L
V o lta g e
tim e
2 ,5 V
3 ,5 V
1 ,5 V
C A N _ H
C A N _ L
re c e s s iv e d o m in a n t re c e s s ic v e
C A N h ig h -s p e e d , n o m in a l b u s le v e ls

25. Controller for CAN

26. Features of Cortex-M3 board
It is based on the NXP LPC1768, with a 32-bit ARM Cortex-M3 core running at 96MHz. It includes
512KB FLASH, 32KB RAM

27. Cortex-M3 exercises
• Blink LED
• Build two bit counter
• Control LED based on switch
• Control the speed of the Motor based on
speed.

28. CAN transceivers

29. CAN project
• Build CAN networks to transmit counter
from one node to other.
• Interior lighting control over CAN bus
• Sending multiple bytes over CAN network

30. What is Ticker?
• Use the Ticker interface to set up a
recurring interrupt; it calls a function
repeatedly and at a specified rate.

31. CANMessage structure

32. CAN Signal Analysis

33. CANalyzer and BUSMASTER

34. CANalyzer/CANoe
• CAN BUS analysis at signal
• CAN bus analysis at message level
• Send/Receive CAN data
• Simulate CAN node
• Simulate CAN network
• Test Automation using CAPL scripting

36. Setting the baud-rate
• Can1.freequency(250000);

37. Sending multiple bytes