Many vehicles in the automobile industry contain miles of cabling wires. It is a well-known phenomenon that this wiring always possesses an augmented threat of accidents like short-circuit or faults; many vehicle manufacturers have started reducing the production for these cablings. In place of these wirings, they have started making use of the CAN Bus architecture. Many people might have come across the term CAN bus and might have wondered what it is exactly and what does the term mean?
The ‘CAN’ in CAN bus stands for ‘Controller Area Network‘. This network is employed to enable the devices and microcontrollers in a vehicle to interact with each other with the assistance of a host system, which manages this entire data acquisition and control.
Cars are not the only vehicles getting affected by increasing wire complexity and weight. There are numerous other vehicles, including boats and yachts, that are facing a similar problem. Hence, to curb this wiring problem in vehicles, the Controller Area Network bus has come to the rescue.
What is a Controller Area Network Bus and how does it work?
The Controller Area Network (CAN) bus has arisen to rule the automobile industry in Europe. Along with this, manufacturers in the United States of America have also started adopting this network. This is why hundreds of billions of Controller Area Network are sold every year; most of these get sold to be fitted in cars.
Now, reading this, most people might wonder what is the reason behind this widespread prevalence is and how does a Controller Area Network Bus work? To start with, the Controller Area Network is usually traded as on-chip peripherals positioned in the microcontrollers.
A standard CAN bus consists of three layers:
- The application layer
- The data-link layer
- The physical layer
When speaking of working, this application layer communicates with the operating system or the application of the Controller Area network device. The data-link layer interacts with the original data and sends, receives and validates this data. The last and the most important layer is the physical layer; it takes care of the entire actual hardware in the CAN Bus. Hence it is pretty evident that the physical layer holds utmost importance and plays a significant role in a vehicle.
For the creation of this physical layer, a pair of knotted multi-drop wire is stipulated. The length of this knotted wire can range anywhere between 1000 meters at the speed of 40 Kbps to a length of 40 meters at a speed of 1 Mbps. The highest payload of the communication carried in this physical layer is 8 bytes, and all communications bear a CRC, which is commonly known as a cyclic redundancy code.
Every message transported in the hardware of the physical layer of the CAN bus holds an identifier. The main purpose of this identifier is to decipher the meaning of the message in the right manner, depending upon the high-level protocol or the application used. All junctions connected to the CAN network get every message; these nodes or junctions then commonly decide whether this message identified is in the interest of the vehicle owner or not.
Picking a CAN bus controller for your vehicle required you to judge the data-link and the psychical portion of a network stack. This network stack is the combined implementation of the computer networking protocol, which can be beneficial to the vehicle in the long run.
In a closed Controller Area Network (CAN) bus system, you can decide on implementing a high-level protocol of your own. However, suppose you wish to interoperate your vehicle’s components with some other vehicle’s. In that case, the manufacturers will most expectedly advise you to make use of standard Controller Area Network (CAN) bus protocols.
For efficient engine management in a vehicle, the J1939 protocol of the Controller Area Network (CAN) bus is the most prevalent. While the open CAN bus protocol is favoured for the body management of the vehicles like lock and lights and the closed CAN bus protocol on the user’s preferred high-level protocol, both these CAN bus protocol functions on the exact same hardware. However, the distinct application requirements are fulfilled by a closed and higher-level CAN bus protocol.
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What is the requirement of a CAN bus protocol?
The requirements of a CAN bus protocol in the automobile sector are completely different from IT and desktop networks. This CAN bus protocol in the automobile sector makes use of Ethernet technology. This ethernet technology can be defined as a protocol that renders physical and data-link specifications to the shared network medium.
The main purpose of using this ethernet technology in an enclosed vehicle environment is that the CAN bus necessitates an enhanced real-time performance. The delay caused by the CAN bus will not affect the entire operations of the vehicle. However, if there is a non-identified element in the CAN bus architecture, then it can become difficult to reimburse for it at the higher stages.
If two Ethernet junctions in a vehicle start communicating at the corresponding time, it can create an abnormal voltage in the vehicle. Hence, the CAN bus protocol is extremely essential for streamlining the communications between the nodes in the vehicles. When the nodes detect a communication, both of these junctions start backing off, which can further delay the vehicle’s functioning.
A properly managed Ethernet interface on the CAN bus is well-equipped to keep these clashes off the nodes. To perform this function, a CAN bus makes use of different approaches. Every communication transmitted on the CAN bus protocol is identified as dominant or recessive, and the system further deciphers this information in the machine language of 0 and 1.
All the junctions in a CAN bus can detect and communicate messages at the corresponding time. If more than one node is conveying the messages, the outcomes will carry the message of the node forward, which is more powerful.
Hence, the most important feature of a CAN bus network is the fact that it classifies the node communication and can place them according to their dominant and recessive bit. The protocol initially identifies the message transmitted, and then if it thinks fit, this message is transferred further to the respective nodes bar. This transmission of data is known as the arbitration field as this CAN bus decides which message is more important and which requires to get transferred first.
Benefits of a CAN bus
1. Economical cost
The main purpose for which the CAN bus protocol was made was to provide lightning-fast communication between the modules and electronic devices used in a vehicle, reducing the wirings in the vehicles at the same time. This reduction in wiring is achieved with the assistance of multiplex wiring. This multiplex wiring is an aggregation of digital and analogue signals and their transportation across a shared medium. This entire process takes place most cost-effectively and is why there is a colossal demand in the CAN bus protocol amongst the automobile manufacturer.
2. In-built error apprehension
Another significant feature of a Controller Area Network bus protocol is the in-built error apprehension. This feature assists in centralized command over automated machines linked to the interface. Every automated machine is known as a node or a junction in the physical layer of a CAN bus. These nodes can interact with all the other junctions (nodes) on the interface, and they necessitate a microcontroller, CAN transmitter and a CAN controller for its operation.
While every node is competent in transmitting and accepting communications, all nodes are not allowed to transmit messages simultaneously. Earlier, when there was no CAN bus protocol, the nodes clashed with each other, which further resulted in a delay in transmitting the messages. Hence to resolve this situation and overcome an in-built error apprehension, the CAN bus protocol was invented. With this protocol’s assistance, the system can easily identify the node that carries the most important message; the nodes are given priority based on the messages they carry.
Apart from this, the process of error handling is also automated in a CAN bus protocol. Every node present in the interface automatically runs an error check and also works towards countering that error. In addition to this, these nodes or junctions convey a specific Error Banner message when errors are identified. It will automatically erase the offending CAN bus traffic to limit it from circulating through the entire interface.
The nodes also self-destruct if they find an error in their self-transmitted message. Hence, in this manner, the CAN bus protocols can both identify faults and limit defective devices from producing dysfunctional bus traffic.
Longevity and security are again the most significant spheres you must keep in mind while choosing a communication protocol for vehicle manufacturing if you are an automobile manufacturer. If you are the end-user, you must look for these key points as well; this is the biggest benefit that the CAN bus protocol holds.
A CAN bus protocol is the most robust and sturdy when the vehicles and other products are deployed in the real market. This is one of the most self-sustaining communication protocols that can carry out operations for a longer duration without any human intervention or maintenance.
This provision of the fault detection ability is extremely advantageous for a CAN bus protocol as it facilitates interfaces to recognize and overcome fallacies on their own without any human intervention. There are basically five mechanisms that the CAN bus protocol employs for detecting errors.
They are known as:
- Bit scrutinization
- Bit framework
- Structure check
- Acknowledgement control
- Cyclic redundancy control
All these mechanisms listed above present the CAN bus protocol with the sturdiness it provides. Due to these mechanisms, a CAN bus protocol can endure high-temperature ranges as well.
Another reason people and automobile manufacturers make use of the CAN bus protocol is its high speed. When this protocol was initially defined, it was divided into three layers known as the application layer, the data-link layer and the physical layer. However, in the later stage, these layers were removed, and only the high speed CAN bus protocol was taken into account.
This high-speed gave designers the complaisance to create CAN bus protocol systems with communication mechanisms and energies that matched their predetermined purposes. In addition to this, to assist the adoption of CAN bus devices and networks, later on, an ISO standard 11898-2 was also released for the physical layer of the Controlled Area Network (CAN) bus protocol.
A high speed CAN bus also extends the high speed ranging between 40 kbps to 1 Mbps, and this speed completely relies on the expanse of the cable. It also uses physical measures to support standard cables for producing higher speed data transmission.
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Apart from all the other benefits, a CAN bus protocol is widely regarded for the pliancy or flexibility it renders. To comprehend the pliancy of the CAN bus protocol in the message transmissions, it is important to distinguish between a message-based protocol and an address-based protocol. The main difference between the two is that in an address based protocol, the nodes in the system can interact with each other by identifying their addresses.
This provision cannot be availed in a message-based protocol as there is no identification address present with the nodes in this protocol. The CAN bus protocol makes use of a message-based communication protocol and hence does not require any address to transmit messages. Due to this, the nodes in the system can be removed or added at any time without any update.
This characteristic works as a benefit for designers as they can effortlessly integrate novel automated devices to the CAN bus protocol, that too, without significant coding overheads. This further makes it easy for engineers to integrate new electronic devices into the CAN bus network without significant programming overheads.
The bottom line
Keeping in mind all the benefits that a CAN bus protocol offers, it can be easily asserted that this protocol is here to stay and will continue to command the automobile sector for many more years ahead. Apart from the automobile sector, it will dominate other industries with its lightning-fast speed and economical pricing. Hence, this communication protocol is worth considering if you are looking for an interactive system.