This blog by Bryan Hennessy will provide updates on the wider topics under discussion within the J1939 committees. Bryan is an experienced engineer in the fields of CAN diagnostics, marine electronics and semiconductors. He is an active member of the SAE Truck and Bus Control and Communications Network Committee and J1939 Task Force and chairs the ‘J1939-21 – Data Link Layer Task Force’.

The Truck Bus Control and Communications Standards Committee (SAE J1939 standards committee) met in Boise, ID in early May for four days of standards development and maintenance. This was the first face-to-face SAE meeting for me since pre-pandemic. The topics included all the usual, and I will report on a few of the more interesting ones including CAN XL, Hybrid/EV, and NextGen.

SAE J1939 over CAN XL

Two subjects that seem to have recently merged into one are Datalink Document Restructuring and CAN XL. Datalink Document Restructuring has been kicked around for close to a year now, and it involves taking the commonality in SAE J1939-21 and -22, and putting them into a single document, then having simpler individual documents describing the differences. The reason this subject has been recently merged with J1939 over CAN XL is that this restructuring would make it easier to generate the CAN XL packaging document. It is thought that document restructuring could bring the documents more in line with the OSI seven-layer communication system model, and therefore make the different layers more usable in other digital communications technologies, including CAN XL.

With that in mind the subject of making a J1939 data packaging layer that would enable transferring data on many different network architectures was discussed. If we standardized how to put J1939 data into a structure that could be packaged into CAN XL frames, Ethernet frames (10BASE-T1S), or any other appropriate network technology, we would really have created something powerful.

The question came up as to when the committee is going to put move value on the 20,000 plus signals that are packaged and well-documented under J1939, and less value on how these signals are transported? Other non-CAN transport methods have already defined and tested security and functional safety methods, as well as prioritization and block-transport protocols, and can be used for J1939 data. What this means is we get more value out of our detailed engine-related control work, and take more advantage of separately defined transport technologies that allow us to move the data through many different networking technologies.

Hybrid/EV considerations

Work continues on defining what parameters will be communicated between different components (motors, generators, inverters, battery packs….) within a hybrid/EV truck, and how those parameters will be packaged. Limit override messages, override timeouts and thermal limits are among the hundreds of parameters being defined. V2G (Vehicle to Grid) communications were also considered, with discussion that included how to work with existing EVSE (Elect Vehicle Service Equipment) standards like SAE J2847-2.

The work undertaken in this area is remarkable, with those involved required to have a huge knowledge of electric and hybrid vehicle design and control.

NextGen

The Next Generation Task Force will be back as of the August 2023 meeting in Portland, OR. The NextGen committee monitors and evaluates new technologies and changes that may affect SAE J1939 in the future and often results in new task forces and new documents. For example, the document restructuring topic outlined above could be moved into NextGen for further analysis and discussion. The best thing about NextGen is that just about anything goes, as long as it relates to technology that could find a home in the trucking industry. We all hope that the resurrection of NextGen will bring new ideas and new momentum to the J1939 committee.