Difference between revisions of "CAN BUS Tutorial"

== CAN BUS ==

== CAN BUS ==

<font color="red"> This article is under construction </font>

<font color="red"> This article is under construction </font>

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*  29-bit

*  29-bit

     | Frame Information            | Message ID  | 0-8 bytes |

     | Frame Information            | Message ID  | 0-8 bytes |

     | RTR, Msg ID Type, Byte Count | 11 or 29-bit | 0-8 bytes |

     | RTR, Msg ID Type, Byte Count | 11 or 29-bit | 0-8 bytes |

*  RTR : Remote transmission frame

*  RTR : Remote transmission frame

=== Message ID Design ===

=== Message ID Design ===

What we can do is split the message id into separate fields so each node on a CAN bus can address any other node:

What we can do is split the message id into separate fields so each node on a CAN bus can address any other node:

     | 4-bit destination id | 4-bit source id | 3-bit message id |

     | 4-bit destination id | 4-bit source id | 3-bit message id |

What we have done now is added the capability that multiple nodes can speak to each other, and whoever has the lowest source id has the highest priority on the CAN BUS.  So suppose that we are a "lights controller" on a vehicle's CAN BUS, then we can specify the following standard :

What we have done now is added the capability that multiple nodes can speak to each other, and whoever has the lowest source id has the highest priority on the CAN BUS.  So suppose that we are a "lights controller" on a vehicle's CAN BUS, then we can specify the following standard :

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== OBDII ==

== OBDII ==

OBDII standard uses CAN BUS to communicate to the ECU.  You can connect a CAN controller to an OBDII port easily by using an [https://www.sparkfun.com/products/10087 OBDII to Serial] cable.  Since this kind of cable doesn't convert the CAN voltage signals to logical signals that a microcontroller can understand, you would also need an MCP2561 based transceiver which would allow your controller to be interfaced to an OBDII port.  

OBDII standard uses CAN BUS to communicate to the ECU.  You can connect a CAN controller to an OBDII port easily by using an [https://www.sparkfun.com/products/10087 OBDII to Serial] cable.  Since this kind of cable doesn't convert the CAN voltage signals to logical signals that a microcontroller can understand, you would also need an MCP2561 based transceiver which would allow your controller to be interfaced to an OBDII port.  

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== Resources ==

== Resources ==

*  TI CAN Bus tutorial

*  TI CAN Bus tutorial

*: [http://www.ti.com/lit/an/sloa101a/sloa101a.pdf CAN Bus]

*: [http://www.ti.com/lit/an/sloa101a/sloa101a.pdf CAN Bus]