MCES Unit 5 Part for engineering students

MCES
Unit V
Automotive Bus System and Diagnostics
Mohammad Faruk Bagwan
Assistant Professor, Department of ECE
MITSOES, MIT ADT University, Loni Kalbhor, Pune

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Automotive Bus System and Diagnostics
1. Automotive Protocols: CAN/J1939, LIN, FlexRay,
MOST, Ethernet.
2. Diagnostics: Fundamentals of Diagnostics,
Diagnostics tools, On-board and off-board
diagnostics in Automobiles, OBDII, Concept of DTCs,
DLC, MIL, Freeze Frames, History Memory,
Diagnostic protocols KWP2000 and UDS.

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Properties of a transmission that a protocol can define
 For example, properties addressed with protocols may include:
 Packet size.
 Transmission speed.
 Error correction types.
 Handshaking and synchronization techniques.
 Address mapping.
 Acknowledgment processes.
 Flow control.
 Packet sequence controls.
 Routing.
 Address formatting.

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What are Communication Protocols
 The proper descriptions of digital message (information)
formats as well as rules are known communication protocols.
 The main function of these protocols is to exchange messages
(information) from one computer system to another.
 These are significant in telecommunications systems as they
consistently send and receive messages.
 These protocols cover error detection & correction, signaling,
and authentication.
 They can also explain the semantics, syntax & brings analog &
digital communications together.

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What are Communication Protocols
 The implementation of these protocols can be done within
hardware as well as software.
 Communications protocols are available around thousand
types which are used all over in analog & digital
communications.
 Protocol: A set of rules and regulations is called a protocol.
 Communication: Exchange of information from one system to
another system with a medium is called communication.
 Communication Protocol: A set of rules and regulations that
allow two electronic devices to connect to exchange the data
with one and another.

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Types of Communication Protocols
 The communication protocols which can be classified below:
 The inter-system protocol using to communicate the two different
devices. Like communication between computer to microcontroller kit.
The communication is done through an inter bus system.
 The Intra system protocol is used to communicate the two devices within
the circuit board. Using intra system protocols circuit complexity and
power consumption, the cost is decreased and it is very secure to
accessing the data.

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Types of Communication Protocols
The different categories of inter system protocol
mainly include the following.
 UART Protocol
 USART Protocol
 USB Protocol
The different categories of intra system protocol
mainly include the following.
 I2C Protocol
 SPI Protocol
 CAN Protocol

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Types of Inter System Protocols: UART
 UART stands for a universal asynchronous transmitter and receiver.
UART Protocols is a serial communication with two wired protocols.
The data cable signal lines are labeled as Rx and Tx. Serial
communication is commonly used for transmitting and receiving the
signal. It is transferred and receives the data serially bit by bit
without class pulses. The UART takes bytes of data and sends the
individual bits in a sequential manner.
 UART is a half-duplex protocol. Most of the controllers have
hardware UART on board. It uses a single data line for transmitting
and receiving the data. It has one start bit, 8-bit data and a one-stop
bit mean the 8-bit data transfer one’s signal is high to low.
 Ex: Emails, SMS, Walkie-talkie.

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Types of Inter System Protocols: UART

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Types of Inter System Protocol: USART
 USART stands for a universal synchronous and asynchronous
transmitter and receiver.
 It is a serial communication of a two-wire protocol.
 The data cable signal lines are labeled as Rx and TX.
 This protocol is used to transmitting and receiving the data
byte by byte along with the clock pulses.
 It is a full-duplex protocol that means transmitting and
receiving data simultaneously to different board rates.
 Different devices communicate with microcontroller to this
protocol.
 Ex:-Telecommunications.

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Types of Inter System Protocol: USB
 USB stands for universal serial bus.
 Again it is a serial communication of two-wire protocol.
 The data cable signal lines are labeled D+ and D-.
 This protocol is used to communicate with the system
peripherals.
 USB protocol is used to send and receive the data serially to
the host and peripheral devices.
 USB communication requires driver software that is based on
the functionality of the system.
 USB devices can transfer data on the bus without any request
on the host computer.

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 Now a day’s most devices are using this technique for
communicating with USB protocol.
 Like a computer to communicate with an ARM controller
using USB.
 USB transfer the data to different modes .first one is slow
speed mode 10kbps to 100 kbps; the second one is full speed
mode 500kbps to 10Mbps, high-speed mode 25Mbps to 400
Mbps.
 USB maximum cable length of 4 meters.
 Ex: Mouse, Keyboard, Hubs, switches, pen drive.

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Types of Intra System Protocol: I2C
communicate the two devices within the circuit board
 I2C is Inter Integrated Circuit and it requires only two wires
connecting all peripherals to the microcontroller.
 I2C requires two wires SDA (serial data line) and SCL (serial
clock line) to carry information between devices.
 It is a master to a slave communication protocol. Each slave
has a unique address.
 The master device sends the address of the target slave
device and reads/writes the flag.
 The address matches any slave device that the device is ON,
the remaining slave devices are disabled mode.

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• Start Condition: The SDA line switches from a high
voltage level to a low voltage level before the SCL line
switches from high to low.
• Stop Condition: The SDA line switches from a low
voltage level to a high voltage level after the SCL line switches
from low to high.

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 Once the address is match communication proceed between
the master and that slave device and transmitting and
receiving the data.
 The transmitter sends 8-bit data, the receiver replies 1-bit of
acknowledgment.
 When the communication is completed master issues the stop
condition.
 The I2C bus was developed by Philips Semiconductors.
 Its original purpose is to provide an easy way to connect CPU
to peripherals chips.

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Types of Intra System Protocol: SPI
 SPI stands for the serial peripheral interface.
 It is one of the serial communication protocol developed by
Motorola.
 Sometimes SPI protocol is also called a 4-wire protocol.
 It requires four wires MOSI, MISO, SS, and SCLK.
 SPI protocol used to communicate the master and slave
devices.
 The master first configures the clock using a frequency.

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 The master then selects the particular slave device for
communication by pulling the chip select button.
 That particular device is selected and starts the
communication between the master and that particular slave.
 The master selects only one slave at a time.
 It is a full-duplex communication protocol.
 Not limited to 8-bit words in the case of bit transferring.

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Types of Intra System Protocol: CAN
 CAN stands for the controller area network.
 It is a serial communication protocol.
 It requires two wires CAN High (H+) and CAN low (H-).
 It was developed by the Robert bosh company in 1985 for in-
vehicle networks.
 It is based on a message-oriented transmission protocol.

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Types of Intra System Protocol: CAN

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Compare Intra System Protocols
 CAN stands for the controller area network.
 It is a serial communication protocol.
 It requires two wires CAN High (H+) and CAN low (H-).
 It was developed by the Robert bosh company in 1985 for in-
vehicle networks.
 It is based on a message-oriented transmission protocol.
I2C SPI CAN
I2C is an inter-integrated circuit
SPI stands for serial peripheral
interface
The CAN stands for controller
area network
It is implemented by Philips SPI is developed by Motorola CAN is developed by Bosch
I2C is a half-duplex protocol SPI is a full-duplex protocol CAN is a full-duplex protocol
Synchronization Synchronization Synchronization
It is a two-wire protocol like SCL
& SDL
It is a four-wire protocol like SCL,
MISO, MOSI & SS
It is a two-wire protocol like
CANH+ and CAN H-
It is a multi-master protocol It is a single master protocol It is a multi-master protocol
It is used in the circuit board It is used in the circuit board It is used in two circuit board

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Compare Protocols

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Automotive Protocols
1. This article gives a detailed introduction to automotive
communication protocols for vehicles.
2. It will illustrate the basics of communications in automotive
systems and inform you about the types of language
protocols available at this point.
3. You’ll learn how protocols are selected for any new feature
and read a case study elucidating that.
4. you’ll learn about current trends in automotive
communication, the state-of-the-art in-vehicle
communication, and get a view of what the leading Protocol
Stack companies are.

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Why is communication needed in automotive systems?
1. In the old days, automotive systems were concentrated on a
few nodes.
2. Now, they’re continuously evolving.
3. 45 to 70 or 80 subsystems can exist in a car carrying out
multiple functionalities.
4. Communication between all these subsystems is essential for
the overall implementation of the vehicle’s features.

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• Why is communication needed in automotive systems?
• Right from vehicle startup till the driver leaves the car, all the
subsystems continuously transmit their status to, as well as
receive data from, other subsystems necessary to perform a
task.
• This is what enables, for example, the hazard lights on the
dashboard lighting up when a door is not properly closed.

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Automotive Protocols: The different protocols available
can broadly be categorized into 3 types:
1. Datalink protocols: Datalink protocols take care of the
physical layer implementation. UART, SPI, I2C, LIN, CAN
(Control Area Network, 90% of all vehicles use CAN for their
communication), Flex-Ray and Ethernet.
2. Application protocols: They use datalink protocols as the
underlying layer. UDS (used for diagnostics, uses CAN as the
data link), J1939, CAN-Open, MOST(used for media-related
communication, used over CAN).
3. Other protocols: Bluetooth, Wi-Fi, USB, 4G/5G
(Vehicle2Network - V2X)

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Datalink protocols: Datalink protocols take care of the physical
layer implementation.
1. UART (serial port communication protocol),
2. SPI (serial peripheral interface),
3. I2C (Inter Integrated Circuit)
4. LIN (Local Interconnect Network),
5. CAN (Control Area Network, 90% of all vehicles use CAN for
their communication),
6. Flex-Ray and Ethernet.

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Automotive Protocols: How does one select a protocol
for a new feature?
1. Maximum ‘payload’ size
2. Bandwidth of the network
3. Maximum bus length supported
4. Network architecture
5. Transfer Mode
6. Fault tolerance
7. Suitability for safety
8. How easy it is to add or remove a node from a vehicle
network

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for a new feature?
1. Maximum ‘payload’ size: ‘Payload’ is the volume of data we
want to transfer from one node to another node. Based on
this, we have to pick an appropriate protocol. Therefore, the
volume of data plays a key role.
2. Bandwidth of the network: The bandwidth of the network is
the maximum available speed for data transmission. We
need to see at what speeds we want to transport the data.
3. Maximum bus length supported: This is important mainly to
resolve challenges related to wiring. For example, in terms of
wiring, the distance between the rear-view camera and the
parking assist system would need to be kept in mind.

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for a new feature?
4. Network architecture: This would address the options we
had of having multiple masters/slaves within the same
protocol.
5. Transfer Mode: This would determine whether the
communication sending protocol is full-duplex or half-duplex,
Simplex. Another parameter that plays into the transfer rate
is synchronous or asynchronous.
6. Fault tolerance: This answers the question of how sure we
are that the data being sent by the sender is received by the
receiving node accurately. Different protocols have different
error-correcting mechanism.

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for a new feature?
7. Suitability for safety: More or less an add-on feature,
nevertheless critical if we want to ensure that all the data is
being received, where every frame of data is acknowledged
being sent back by the receiver.
8. How easy it is to add or remove a node from a vehicle
network: For example, with CAN one could do it with two
lines, but many other protocols would require hardware
changes.

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Automotive Protocols: a concrete example to
demonstrate
Consider the case study of reverse parking.
1. The moment the car is put in reverse, the rear-view camera will be
activated and the camera module will start recording data.
2. The camera module is connected to Park Assist ECU using Ethernet.
3. Now, Park Assist provides the live video feed over Ethernet to
Infotainment or Instrument Cluster for displaying to the driver.
4. As part of this, it also provides an overlay to the live feed: “We are ten
minutes away from crashing into the curb” or some such.
5. Ethernet is chosen because a huge amount of data shall be sent
continuously.
6. The network design has to be chosen with respect to the network
packaging, how we want to send the data.

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Current trends in automotive communication
 Traditional ECUs continue to use CAN, either 2A or 2B
networks, using an 11 bit or a 29-bit identifier.
 Depending on whether one needs low speed (125 kbps) for
normal networks or high speeds (500 kbps or 1 Mbps) for
critical features.
 The two can coexist, and are interconnected using CAN
gateways for exchange.
 LIN is used for less critical communication.
 CAN-LIN gateways are used for data exchange between CAN
and LIN sub-networks.

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Current trends in automotive communication
Nowadays one has
 CAN-FD,
 CAN-Flexible-Datarate, which has data speed up to 5 Mbps, or
 Flex-Ray which has data speed of up to 10 Mbps.
 The very latest applications like ADAS, Telematics Units use
Ethernet or Wireless (4G or 5G) based communication
because they have specific payload/bandwidth demands.

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Automotive Protocols: LIN, CAN, FlexRay, MOST
 LIN stands for Local Interconnect Network, It is used in a low-
level communication system. It may be used to make a
connection between sensors and controllers. For example: In
the body of the vehicle.
 CAN stands for Controller Area Network, CAN is used in soft
real-time systems. For example: In engines, power trains,
chassis, battery management systems, etc.
 MOST stands for Media Oriented System Transport, MOST are
used in media-related applications and control in automotive.
For example: In multimedia, telematics, etc.
 FlexRay, FlexRay is used in a hard real-time system. For
example: In power trains, chassis.

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LIN, CAN, FlexRay, MOST (Architecture)
 LIN has a single master and typically 2 to 10 slaves.
 CAN has a multi-master and typically 10 to 40 nodes.
 FlexRay has a multi-master and up to 64 nodes.
 MOST also have multi-master and up to 64 nodes.

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LIN, CAN, FlexRay, MOST (Bus Access)
Bus it is a communication system that is responsible for data
transfer.
 LIN has polling bus access
 CAN has CSMA/CA bus access (carrier sense multiple access)
 FlexRay has TDMA/FTDMA bus access (time
division/Frequency and time division multiple access)
 MOST have TDM CSMA/CS bus access

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LIN, CAN, FlexRay, MOST (Bus Access)
Topology means it is an arrangement made to connect devices.
 LIN has a bus topology
 CAN also have bus topology
 FlexRay has BUS/Star topology
 MOST have a ring/star topology

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LIN, CAN, FlexRay, MOST (Transmission)
 In LIN, message transmission is synchronous.
 In CAN, message transmission is asynchronous.
 In FlexRay, message transmission is synchronous and
asynchronous.
 In MOST also, message transmission is synchronous and
asynchronous.

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LIN, CAN, FlexRay, MOST (Data Rates)
• In LIN, the data rate is 20 Kbps.
• In CAN, the data rate is 1 Mbps.
• In FlexRay, the data rate is 10 Mbps.
• In MOST, the data rate is 24 Mbps.

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LIN, CAN, FlexRay, MOST (Physical Layer)
 An electrical single wire is used in the LIN protocol.
 The electrical dual wire is used in CAN protocol.
 Dual wire – optical or electrical wire is used in FlexRay.
 The optical fiber cable is used in MOST.

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Thank You
 Will be continue in next class….

MCES Unit 5 Part for engineering students

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