Development of SAE J1939 protocol stack based on NXP MPC5744P

Summary

This note mainly records the development and interface design of the SAE J1939 protocol stack based on NXP MPC5744P, based on the CAN driver design summarized previously.

Preparation

Prepare a project where the CAN driver can work properly.

Familiar with J1939 protocol documents and standards, especially J1939-21 and J1939-81.

CAN

NXP's MPC5744P controller local area network CAN has basically the same structure as the NXP Kinetis KV and other series of flexCAN we used before. MPC5744P supports CAN2.0B. CAN's high-level protocol, J1939, is an extended frame based on CAN2.0B, a 29-bit identifier, and supports single-frame and multi-frame transceiver communication. This design mainly implements the SAE J1939 data link layer and network management layer.

J1939 and CAN interface

Interface function

Based on the CAN driver made last time, it provides a sending function and a receiving processing function as an interface with the J1939 protocol stack to complete the implementation and application of all J1939 functions.

The receiving interface is used to obtain the CAN message frame on the bus, which is then parsed by the J1939 processing function. This send function is not listed.

type of data

The following data types are specifically defined according to the standards and requirements of J1939 to facilitate program development and application.

J1939 external interface

Except for initialization, the J1939 external interface has only one function. All functions are implemented in this function. Because there are many time bases inside the J1939 protocol stack, the design is based on 10ms, so this function is called in 10ms.

test

The SAE J1939 protocol is a high-level protocol of CAN. It is widely used in heavy-duty vehicles, special vehicles, agricultural machinery, and non-road equipment vehicles.

The SAE J1939 protocol stack mainly refers to the standards J1939-21 data link layer and J1939-81 network management layer. For details of the standard, please refer to SAE's J1939 standard.