A Brief Info on CAN Frame and CAN Standardized Communication Protocols

CAN Stack is based on an?in-vehicle networking (BUS) standard that allows multiple electronic control units to interact with one another. The CAN Stack protocol is a serial communication system used mostly in passenger automobiles.

It enables significantly higher data rates of up to 500 kbps. The data rate can be raised further by using the CAN Transport layer (ISO 15765).

What is CAN Frame?

CAN frames are used to communicate via the CAN bus.

The image below shows a conventional CAN frame with an 11-bit identifier (CAN 2.0A), which is the type used in most automobiles. The CAN ID and Data are critical when capturing CAN bus data.

Except for the longer ID, the extended 29-bit identification frame (CAN 2.0B) is identical. It is used, for example, in the J1939 protocol for heavy-duty automobiles.

[image source: CSS Electronics]

How are CAN, J1939, OBD2 and CANopen Connected?

The Control Area Network lays down a basis for communication in vehicles. However, there are other functions that are performed by a set of standardized communication protocols that are precisely linked to the CAN Bus.

The CAN standard does not describe how to handle messages with lengths greater than 8 bytes, or in addition,?how to decode raw data. As a solution to this, there is a set of defined protocols?in place to further clarify how data is transmitted between CAN nodes in a given network. These protocols come under ISO TP layer defined by ISO 15765.

SAE J1939, OBD2, and CANopen are some of the most commonly used standards.

• J1939 is the industry standard for in-vehicle networks in heavy-duty vehicles.??J1939 parameters (such as RPM, speed, and so on) are identified by a suspect parameter number (SPN), which is then organized into parameter groups identified by a PG number (PGN).
• On-board diagnosticsISO 15031) is a self-diagnostic and reporting feature used by mechanics to identify vehicle problems. OBD2 defines diagnostic trouble codes (DTCs) as well as real-time data (e.g., speed, RPM) that can be captured using OBD2 scanners.
• CANopen is frequently utilized in embedded control applications such as industrial automation. It is based on CAN, which means that a CAN bus data logger can also log CANopen data. This is critical in areas such as machine diagnostics and production optimization.

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