SAE J1939 Improves Communication
As vehicles become more sophisticated, electronics are playing an important role in the execution of various tasks. Traditionally, Electronic Control Units (ECUs) have been used to to manage the various independent systems on a vehicle that include engine control, transmission control, and body control. Now many specialty vehicle manufacturers also supply sub-control systems to existing OEM chassis which adds to the overall complexity.
The challenge lies in managing multiple control systems on one vehicle. Each system requires a separate wiring harness that results in excessive wiring – sometimes extending more than a mile. And, the number of redundant I/O devices quickly adds costs. Enabling these separate systems to share information and “talk” to each other can improve overall vehicle functionality and performance.
The SAE J1939 standard can now be used to bridge these independent systems. Originally developed as a communication network for diesel powertrain components, SAE J1939 is now being used as an application layer to provide communication between the engine control, transmission control, vehicle body control and specially designed sub-control systems.
SAE J1939 serves as the application layer on top of the existing CAN 2.0b physical and data link layers. This allows for the use of existing off-the-shelf CAN transceivers.
SAE J1939 network includes:
Like other CAN-based networks, J1939 packets contain eight bytes of process data. An individual packet also contains an index or Parameter Group Number (PGN) which is incorporated inside the 29-bit identifier. The PGN usually contains multiple SPNs (Suspect Parameter Number). The SPN determines the type of data, the resolution of the data, and the range of the data while PGN specifies how often it’s transmitted.
As a typical example, the first byte of PGN 65262 contains SPN 110 which is responsible for coolant temperature, the resolution is 1°C per bit, the range is -40...210°C and the transmission rate is 1 second. The predefined PGNs cover a wide range of different types of information for mobile equipment.
Ifm offers integrated SAE J1939 connections on many control products for powertrain information exchange in the machine application.
The challenge lies in managing multiple control systems on one vehicle. Each system requires a separate wiring harness that results in excessive wiring – sometimes extending more than a mile. And, the number of redundant I/O devices quickly adds costs. Enabling these separate systems to share information and “talk” to each other can improve overall vehicle functionality and performance.
The SAE J1939 standard can now be used to bridge these independent systems. Originally developed as a communication network for diesel powertrain components, SAE J1939 is now being used as an application layer to provide communication between the engine control, transmission control, vehicle body control and specially designed sub-control systems.
SAE J1939 serves as the application layer on top of the existing CAN 2.0b physical and data link layers. This allows for the use of existing off-the-shelf CAN transceivers.
SAE J1939 network includes:
- 3-wire cable up to 40m
- Max. 30 nodes
- Uses 29-bit identifier
- 250 K Baud rate
- High EMI resistance
- Simple install and setup
- Enhanced diagnostics
Like other CAN-based networks, J1939 packets contain eight bytes of process data. An individual packet also contains an index or Parameter Group Number (PGN) which is incorporated inside the 29-bit identifier. The PGN usually contains multiple SPNs (Suspect Parameter Number). The SPN determines the type of data, the resolution of the data, and the range of the data while PGN specifies how often it’s transmitted.
As a typical example, the first byte of PGN 65262 contains SPN 110 which is responsible for coolant temperature, the resolution is 1°C per bit, the range is -40...210°C and the transmission rate is 1 second. The predefined PGNs cover a wide range of different types of information for mobile equipment.
Ifm offers integrated SAE J1939 connections on many control products for powertrain information exchange in the machine application.
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