Modern car today like an a small computer where everything is connected
each other in the same network. It have a few network normally used in
car like a Controller area network(CAN), Local Interconnect
network(LIN), Media Oriented System Transport(MOST) and FlexRay. The
most used is
CAN Bus.
CAN BUS allow ECU communicate each other without host computer. Before, in Old car, the number of ECU is less because low demand on the technology. Today, with current technology, a modern Car have a more than 70 ECU. How it looks like if everything is connected using old way? Hard wire?
That the reason in mid-1980, Bosch design CAN Bus to reduce costs and complexity inside the vehicle.
CONTROLLER AREA NETWORK(CAN)
CAN is a serial communication bus where allow ECU in car communicate each other robustly with maximum bit rate of 1Mb/s for high speed. It is a mist suitable for systems where a small amount information needs to be exchange. Instead of automotive, it been used in other industry as well like elevators, robotics, medical and building automation.
It is implemented using pair of differentially signalled wire which is CAN-H and CAN-L. Bits can be either dominant(0) or recessive(1) where dominant win arbitration over recessive and win the bus to allow the winner ECU transmit the data on the bus.
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CAN SIGNAL |
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CAN is a based message network rather than address-based. Means that every node can send a message to all node at the same time. Every node has a filter, means that nodes always filter which message it need and ignore the rest.
CAN using CSMA/CD which is carrier sense multiple access/collition
detection protocol. When a node want to send message over the network,
it must monitor the bus first, and if the bus is idle, it start to
transmit. If two node transmit a message at the same time, a collision
detection. This issue is solved by looking on the ID which are more
priority. The highest priority is always win the bus.
Lets prove with Arduino:)
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