Authors: Paul Suvarov, Alexandru Stancu
"Dunrea de jos" University of Galati, Faculty of Electrical and Electronic Engineering
"Dunrea de jos" University of Galati, Faculty of Computer Science
Year of publication: 2008
Automatic systems
Automated systems are becoming increasingly complex due to rapid technological progress, the number of sensors increases increasing the amount of information to be communicated, as well as the complexity of the electrical system. For this reason it was necessary to develop a simple, cheap and flexible communication system.
CAN (Controller Area Network) bus
The CAN highway was developed by German company Bosch in the mid-1980s. This highway has spread more and more in the industry, on the medical equipment market, the measurement and testing equipment market.
CSMA / CD communication protocol
The communication protocol underlying the CAN bus is CSMA / CD (Carrier Sense Multiple Access with Collision Detection). This protocol provides all nodes with simultaneous access to the communication environment.
Each node must listen to the bus for a certain period of inactivity before attempting to issue a packet. (Carrier detection - CS). After this period of inactivity elapses, each node has equal chances for transmission (Multiple access - MA).
If two nodes in the network start transmitting at the same time, they will detect the collision and act to eliminate the conflict. (Collision Detection - CD).
Non-destructive hardware logic is used to arbitrate the conflict. This arbitration takes place without corrupting the priority package, and also without introducing delays.
CAN-BUS bus
CAN-BUS uses a differential bus, consisting of 2 twisted wires. This provides great immunity to noise.
The signaling speed is maximum 1Mbit / s for a bus with a length of 40m. The length of the bus can be increased by the price of the signaling speed (for 1Km we have 360kbit / s).
Course structure
- Introduction
- CAN-BUS features
- System description
- Block diagram of the system
- Execution node
- CAN-BUS communication circuit
- Monitoring and control node
- Software relations
- Example of automatic system implemented on CAN-BUS
- conclusions
- Work proposals for the future
To better understand CAN (Controller Area Network) communication, I have attached the video below:
I worked with CAN. Differential signal about USB with D + and D-. You had a CAN transceiver, an integrated Rx and Tx signal, like a kind of TTL. The serial data packet started with an ID, such as ID, speed, and then value. When two nodes wanted to emit at the same time, one detects the other's emission and lets the one with the highest priority emit.