Have you ever wondered how your car is following
command to perform any task? How all the sensors, warning lights, control
modules of your car are communicating with each other to give you a flawless
beautiful ride.
Behind this, lots of things are going on to provide a proper channel to
communicate with each other.
In early days, gauzes, modules and warning lights were simply connected directly to sensors. Due to this, there is an addition of a large number of sensors is employed which results in a large number of cables to
connect with each other to communicate. Such interconnections between them
make it complex. And it also adds up the considerable weight to car or
vehicle.
So to cope up with his problem a new communication protocol comes in the image as CAN
Protocol.
CAN (Controller Area Network)
CAN (Controller Area Network) is a serial communication BUS system which is designed for robust and flexible performance in harsh
conditions particularly for industrial application.
CAN was first developed by Robert Bosch in 1982.
CAN communication is widely used in the automobile industry,
drones and industrial automation. This protocol simplifies the monitoring and
diagnosis of detected faults.
In the earlier time, there was a lesser number of sensors and
modules in the car. Point to point connections used to make with hard wire for
communication because they did not need to be linked together for exchanging
real-time information.
But in today’s era, there are strict norms for environmental
regulations and emission norms. Such circumstances require to have more modules,
sensor and also, they have to share information in real-time.
CAN allows various modules to communicate with each other in
a common cable. ‘All ECUs communicate effectively without a central Computer.’
CAN communication can be done by only 2 hard wires. Wires
are twisted pair cables with bus length 40 m and the maximum node would be 30 nodes
with terminal resistance of 120 ohms.
Generally, CAN cable consist of 2 twisted hard wires with a
metallic mesh as a covering.
Yellow Colour wire = CAN High Wire - (1)
Green Colour wire = CAN Low Wire - (0)
Metallic mesh as a covering on wires is provided to reduce
noise occurring in the communication channel.
CAN Signal is a differential Signal. Current flowing in each
is same but opposite in direction which results in field cancellation effect
due to which there is a low noise emission. This ensures low noise and a high
rate of transmission over wires.
In Automobiles, we generally use two types of CAN bus
protocol.
- 1 High Speed CAN
- 2 Low Speed / Fault-Tolerant CAN
-
High Speed CAN
ISO 11898-2 High Speed CAN |
It allows speed up to 1 MBPS and use a linear bus with
termination resistance of 120 Ohms at both ends.
-
Low Speed / Fault-Tolerant CAN
In Low-Speed CAN (ISO 11898-3), the termination resistors
are located at each module and overall resistance is around 100 ohms. On having
terminal resistance at each module, it can also communicate in case of wire
failure.
The transfer rate is around 40 Kbps to 125 Kbps.
CAN Bus Connector
CAN Communication is accessed by OBD (On Board Diagnostic)
Port. OBD is the vehicle’s diagnostic and reporting system. This is the same port
which is used for troubleshooting error codes and for software updates.
On occurring problems in CAN communication channel, DTC
(Diagnostic Trouble Codes) arises as “U” trouble codes with the illumination of
Check Engine Light of vehicle.
We can check the proper functionality of parts of the vehicle by
plugging in the Diagnostic Tool of that particular part. For example, We can
use diagnostic tool for Engine, Transfer Case, Transmission, ABS (Antilock
Braking System).
OBD is 16 pin connector. Generally, Pin number 4 & 5 is kept ground, pin number 6 & 14 is used as diagnostic socket and pin number 16 is kept 12 Volt supply.
OBD is 16 pin connector. Generally, Pin number 4 & 5 is kept ground, pin number 6 & 14 is used as diagnostic socket and pin number 16 is kept 12 Volt supply.
Advantages of CAN:
- LOW COST
On using CAN protocol, all modules, sensors communicate
through via a single CAN Bus. It eliminates all other hard wires which result
in the reduction of cost as well as the considerable weight of the vehicle. It also reduces
faults and errors.
- CENTRALIZED
As all sensors and modules are connected through a single
wire so it provides a central way to detect faults across all the modules and
sensors present in the car.
- ROBUST
Having protection against Electromagnetic Interference makes
it robust and fully functional without any noise or interference in the
communication channel.
- FLEXIBLE
We can easily add or remove any module without hampering of
communication between other peripherals and can easily modify & update their
software.
- EFFICIENT
CAN messages are prioritized via IDs so that the highest priority
ID is non-interrupted.
In today's era, CAN is widely using in Automative industry, Drone technology and in the automation industry.CAN is a central controller that monitors all the car’s system and sensors. In other words, it's a nervous system of a vehicle.
In today's era, CAN is widely using in Automative industry, Drone technology and in the automation industry.CAN is a central controller that monitors all the car’s system and sensors. In other words, it's a nervous system of a vehicle.
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