CAN Bus - Revision history

JvB: /* CAN FD */

2024-06-28T12:05:35Z

CAN FD

Satiric: Specify that the included tables are for the data frame

2023-06-22T01:24:24Z

Specify that the included tables are for the data frame

Satiric: Fill out frame format tables

2023-06-22T01:19:29Z

Fill out frame format tables

Satiric: begin adding frame format tables

2023-06-22T00:58:38Z

begin adding frame format tables

Satiric: Reorganize into layers to make more sense

2023-06-22T00:56:28Z

Reorganize into layers to make more sense

Satiric: Add cable impedance spec, add wiring section.

2023-01-29T20:00:14Z

Add cable impedance spec, add wiring section.

Satiric: /* High–Speed CAN */

2023-01-29T19:40:15Z

High–Speed CAN

Satiric: Expand on CAN bus

2023-01-22T00:29:34Z

Expand on CAN bus

Donnellca: Link back to Communication Protocols

2022-04-09T01:16:46Z

Link back to Communication Protocols

Virtualras at 03:37, 8 September 2020

2020-09-08T03:37:13Z

@@ Line 151: / Line 151: @@
 ===CAN FD===
 CAN FD (Flexible Data-rate) is an extension of the CAN 2.0 protocol. It can dynamically switch between different data rates and longer or shorter messages, resulting in faster data speeds and higher data capacity.<ref>Falch, Martin. "CAN FD Explained - A Simple Intro [2022] - CSS Electronics". Retrieved 2023-01-21. https://www.csselectronics.com/pages/can-fd-flexible-data-rate-intro.</ref>
 ==CAN bus application layer==
 ===J1939===
 ===CANopen===
 ==References==

@@ Line 17: / Line 17: @@
 Because of its low speed it is not often used in the automotive world, but if you don't have a lot of data to send it could be useful.
-==CAN bus data link layer==
+==CAN bus data link layer==<!-- TODO: expand on types of frames: remote request frames, error frames, etc. -->
 The CAN 2.0 protocol is specified in ISO 11898-1. It is split into CAN 2.0A and CAN 2.0B, the original 11 bit identifier version and the extended 29 bit identifier version.
 ===CAN 2.0A===
 CAN 2.0A is effectively the same as CAN 1.0 and 1.2. It uses 11 bit identifiers, so a maximum of 2048 devices can transmit on a network. If a device says it supports CAN, it supports this.
 {| class="wikitable"
 |-
@@ Line 81: / Line 82: @@
 ===CAN 2.0B===
 CAN 2.0B builds on CAN 2.0A by allowing 29 bit identifiers.
 {| class="wikitable"
 |-

@@ Line 23: / Line 23: @@
 {| class="wikitable"
 |-
-|Field name<br />
+!Field name
-|Length (bits)<br />
+!Length (bits)
-|Purpose<br />
+!Purpose
 |-
-|<br />
+|Start of frame
-|<br />
+|1
-|<br />
+|Denotes the start of frame transmission
 |-
-|<br />
+|Identifier
-|<br />
+|11
-|<br />
+|A unique identifier which also represents the message priority
 |-
-|<br />
+|Remote transmission request (RTR)
-|<br />
+|1
-|<br />
+|Must be 0 for data frames and 1 for remote request frames
 |-
-|<br />
+|Identifier extension bit (IDE)
-|<br />
+|1
-|<br />
+|Must be 0 for base format with 11 bit identifiers
 |-
-|<br />
+|Reserved bit (r0)
-|<br />
+|1
-|<br />
+|Reserved bit. Must be 0
 |-
-|<br />
+|Data length code (DLC)
-|<br />
+|4
-|<br />
+|Number of bytes of data (0-8 bytes)
 |-
-|<br />
+|Data field
-|<br />
+|0-64
-|<br />
+|Data to be transmitted (length in bytes determined by DLC field)
 |-
-|<br />
+|CRC
-|<br />
+|15
-|<br />
+|[https://en.wikipedia.org/wiki/Cyclic_redundancy_check#CRC-15-CAN Cyclic redundancy check]
 |-
-|<br />
+|CRC delimiter
-|<br />
+|1
-|<br />
+|Must be 1
 |}
 ===CAN 2.0B===
 CAN 2.0B builds on CAN 2.0A by allowing 29 bit identifiers.
 {| class="wikitable"
 |-
-|Field name<br />
+!Field name<br />
-|Length (bits)<br />
+!Length (bits)<br />
-|Purpose<br />
+!Purpose<br />
 |-
-|<br />
+|Reserved bits (r1, r0)
-|<br />
+|2
-|<br />
+|Reserved bits which must be set 0, but accepted as either 0 or 1
 |-
-|<br />
+|Data length code (DLC)
-|<br />
+|4
-|<br />
+|Number of bytes of data (0-8 bytes)
 |-
-|<br />
+|Data field
-|<br />
+|0-64
-|<br />
+|Data to be transmitted (length in bytes determined by DLC field)
 |-
-|<br />
+|CRC
-|<br />
+|15
-|<br />
+|[https://en.wikipedia.org/wiki/Cyclic_redundancy_check#CRC-15-CAN Cyclic redundancy check]
 |-
-|<br />
+|CRC delimiter
-|<br />
+|1
-|<br />
+|Must be 1
 |-
-|<br />
+|ACK slot
-|<br />
+|1
-|<br />
+|Transmitter sends 1 and any receiver can assert a 0
 |-
-|<br />
+|ACK delimiter
-|<br />
+|1
-|<br />
+|must be 1
 |-
-|<br />
+|End of frame (EOF)
-|<br />
+|7
-|<br />
+|all bits must be 1
 |-
-|<br />
+|Inter-frame spacing (IFS)
-|<br />
+|3
-|<br />
+|all bits must be 1
 |}
 ===CAN FD===
 CAN FD (Flexible Data-rate) is an extension of the CAN 2.0 protocol. It can dynamically switch between different data rates and longer or shorter messages, resulting in faster data speeds and higher data capacity.<ref>Falch, Martin. "CAN FD Explained - A Simple Intro [2022] - CSS Electronics". Retrieved 2023-01-21. https://www.csselectronics.com/pages/can-fd-flexible-data-rate-intro.</ref>

@@ Line 6: / Line 6: @@
 * the data link layer, which specifies bit timing, message framing, error detection, etc.
 * the application layer, which specifies things like which identifier to use for what data.
 ==CAN bus physical layer==
 At the physical layer, there are two types of CAN networks: low–speed CAN and high–speed CAN.
@@ Line 20: / Line 21: @@
 ===CAN 2.0A===
 CAN 2.0A is effectively the same as CAN 1.0 and 1.2. It uses 11 bit identifiers, so a maximum of 2048 devices can transmit on a network. If a device says it supports CAN, it supports this.
-<!--insert frame format table here -->
+{| class="wikitable"
 ===CAN 2.0B===
 CAN 2.0B builds on CAN 2.0A by allowing 29 bit identifiers.
-<!--insert frame format table here -->
+{| class="wikitable"
 ===CAN FD===
 CAN FD (Flexible Data-rate) is an extension of the CAN 2.0 protocol. It can dynamically switch between different data rates and longer or shorter messages, resulting in faster data speeds and higher data capacity.<ref>Falch, Martin. "CAN FD Explained - A Simple Intro [2022] - CSS Electronics". Retrieved 2023-01-21. https://www.csselectronics.com/pages/can-fd-flexible-data-rate-intro.</ref>
@@ Line 29: / Line 116: @@
 ===J1939===
 ===CANopen===
 ==References==

@@ Line 1: / Line 1: @@
 [[Category:Electronics]]
 CAN bus is a [[Communication Protocols|Communication Protocol]] and networking standard designed for communicating between devices in vehicles. Because of its versatility and relatively low complexity, it is used in the vast majority of vehicles manufactured today. By letting multiple devices communicate with each-other through a common interface, wiring harness complexity can be reduced.
-==Types of CAN Bus Networks==
-There are several types of CAN networks: low–speed CAN and high–speed CAN. There is also [[#CAN FD]], described below.
+Computer networks can be thought of as having layers. CAN bus has 3 main layers:
 ===High–Speed CAN===
 [[File:CAN ISO11898-2 Network.png|thumb|Example of a high–speed CAN network.]]
@@ Line 8: / Line 13: @@
 ===Low–Speed CAN===
 [[File:CAN ISO11898-3 Network.png|thumb|Example of a low–speed CAN network.]]
-Low speed is limited to a speed of 125 Kb/s, but it is more flexible in its routing. It can be connected as a star bus with no issues, and each device on the network has two termination resistors. Their value can be calculated based on the method described on page 4-10 of this document from National Instruments: [https://www.ni.com/docs/en-US/bundle/ni-can-hw-sw-seri/resource/370289t.pdf].
+Low-speed CAN (ISO 11898-3) is limited to a speed of 125 Kb/s, but it is more flexible in its routing. It can be connected as a star bus with no issues, and each device on the network has two termination resistors. Their value can be calculated based on the method described on page 4-10 of this document from National Instruments: [https://www.ni.com/docs/en-US/bundle/ni-can-hw-sw-seri/resource/370289t.pdf].
-===Data Format===
-===History===
+Because of its low speed it is not often used in the automotive world, but if you don't have a lot of data to send it could be useful.
-==CAN FD==
+==CAN bus data link layer==
-CAN FD (Flexible Data-rate) is an extension of the original CAN protocol. It can dynamically switch between different data rates and longer or shorter messages, resulting in faster data speeds and higher data capacity.<ref>Falch, Martin. "CAN FD Explained - A Simple Intro [2022] - CSS Electronics". Retrieved 2023-01-21. https://www.csselectronics.com/pages/can-fd-flexible-data-rate-intro.</ref>
+The CAN 2.0 protocol is specified in ISO 11898-1. It is split into CAN 2.0A and CAN 2.0B, the original 11 bit identifier version and the extended 29 bit identifier version.
-===Electrical Specification===
+===CAN 2.0A===
-===Data Format===
+CAN 2.0A is effectively the same as CAN 1.0 and 1.2. It uses 11 bit identifiers, so a maximum of 2048 devices can transmit on a network. If a device says it supports CAN, it supports this.
-===History===
+<!--insert frame format table here -->
-==Wiring==
+===CAN 2.0B===
-In the wiring harness, CAN should be routed as a twisted pair.<ref>Corrigan, Steve. "Introduction to the Controller Area Network (CAN)". Retrieved 2023-01-29. https://www.ti.com/lit/an/sloa101b/sloa101b.pdf.</ref> In practice, it's probably a good idea for this to be shielded twisted pair unless you're knowledgeable about EMI. As stated above, technically High-Speed CAN needs cable with an impedance of 108-132 ohms, but in practice most twisted pair cable will be good enough.
+CAN 2.0B builds on CAN 2.0A by allowing 29 bit identifiers.
 ==References==

@@ Line 3: / Line 3: @@
-CAN bus is a networking standard designed for communication between devices in an automotive environment. Because of its versatility and relatively low complexity, it is used in the vast majority of vehicles manufactured today. By letting multiple devices communicate with each-other through a common interface, wiring harness complexity can be reduced.
+CAN bus is a [[Communication Protocols|Communication Protocol]] and networking standard designed for medium range communication between devices in an automotive environment. Because of its versatility and relatively low complexity, it is used in the vast majority of vehicles manufactured today. By letting multiple devices communicate with each-other through a common interface, wiring harness complexity can be reduced.
 ==CAN==
 ===Electrical Specification===