When we talk with our friends, we share our emotions and thoughts by using certain language. If someone is talking and others can understand, then we will say it is communication; otherwise, it is just noise. Similar ways exist in electronics. Also, if two or more devices are talking to each other, I mean sending or receiving data on any medium, mostly cables or PCB tracks. Everyone should understand that data, right? That's why some rules are imposed on electric signals produced by devices over the Bus so that every device/node on the bus can understand the significance of the change in signals. These rules can take the form of fixation of bit positions, frequency of the signal, amplitude of signals, etc. In digital electronics, amplitudes stay the same as part of the same rules set. If these signals are packed with meaningful bit positions, that is, if a particular number of bits has a particular meaning, then this becomes frame format. hope you understand... Let's move ah...
The Controller Area Network (CAN) protocol is cornerstone of modern communication of embedded systems, which enables reliable data exchange between multiple electronic control units. By understanding how CAN works you can get good help in interview cracking and also increase your knowledge base in automotive domain. Yahh this blog is specially designed to teach you bout CAN, Peoples working in automotive domain should go through this complete series of CAN protocol. Here, we will understand step by step explanation related to can so that you will tackle it with real time application and issues occurs in CAN network node development.
Multi-Master Message-Based Design
We have learned in chapter 1, that CAN Is a multi-master communication protocol which works on broadcasting mechanism. This network ensures that any node can transmit its message when the CAN bus is ideal. in case any node gets fails, there will be no effect on other nodes connected to network. more and more what will happen some on the nodes was taking some information from failed node, that information they will not get, but Node will be working always and network will be healthy always.
lets see something interesting about CAN ECU's (electronic control unit) ,before that note it that we will call them Node's in further topics.
Each Node has some extra circuitry which we already mentioned in chapter 1, that is CAN transceiver along with controller and its supporting circuit. Controller prepares the data to transmit over CAN bus, while transceiver converts it into electrical signals compatible with physical bus.
in the above description, i would like to add some technical aspects as below:
If you have an electronics background, then you may know microcontrollers or processors work on 0 to 3.3V OR 0 to 5V or maybe another range. but CAN works in 1.5 V to 3.5 V range.
Wait..........we have another new concept is to learn to hear .........
CAN has two wires i.e. CAN HISH and CAN LOW. Both have different voltage levels in the physical bus.
The LOW bit on the CAN HIGH and CAN LOW wire is 2.5 V, but the HIGH bit on the CAN HIGH and CAN LOW wire is 3.5V and 1.5, respectively.
let's understand withan example, observe the below picture, which shows some wave forms
So in the above image controller is trying to send binary data 1110111010100111 and the green waveform is showing the actual CAN tx pin waveform, this waveform is captured by tapping CAN tx pin which is connected to the CAN transceiver's CAN rx pin and it converts this digital data in to CAN H, and CAN L voltage level, red and blue waves are showing the taped waveform of CAN H and CAN L respectively.
Hope you understand the concept, still if you have queries leave msg in the comments below this article.
In the next chapter, we will see the frame formats of the CAN standard and CAN extended.
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