The following is an update on the development (firmware plus supporting Windows monitoring tool) of our newest product, the SAE J1939 Gateway Module With USB Port, RTC, MicroSD Memory Card as shown here to the left. 

The JCOM.J939.USB-X SAE J1939 Processor board is an extended version of our popular JCOM.J9139.USB-B SAE J1939 ECU Simulator Board With USB Port.

The improved features are:

• Upgraded ARM Cortex-M3 processor with double Flash & RAM
• Supports Hi-Speed USB 2.0 transfer rate at up to 480 Mbps
• Additional UART-USB for onsite firmware programming
• Onboard Real-Time Clock (RTC) for CAN Bus message timestamp support
• MicroSD Memory Card support
• 4-position DIP switch (one for termination resistor, three for functionality settings)
• Additional serial (UART) port for GPS sensor or SAE J1708 board

The firmware has now been updated to include a timestamp for every received SAE J1939 data frame (PGN), including "loop-backed" messages (i.e. data frames transmitted by the gateway and displayed by the JCOMJ1939Monitor program).

This free-of-charge Windows software allows the monitoring, simulating, and recording of SAE J1939 data frames (PGN). It detects automatically whether or not the attached JCOM.J1939 board supports time-stamping (i.e. represented by the onboard real-time clock) and adjusts the data view list accordingly.

The following shows a screenshot of the current version:

At first glance, the changes are hardly noticeable, but the data view list (bottom of the screen) now shows the time when the CAN Bus message was received. The resolution is 1 msec, which is more than sufficient for SAE J1939 data (regular CAN Bus data at, for instance, 1 MBit/sec would require a resolution of 1 microsecond).

The program synchronizes the time between the PC and the gateway with the PC being the relevant source. That also means that the gateway, while accessing its onboard RTC, does not require a battery when working in combination with the monitor program. 

However, the battery will be mandatory after we have added further firmware functionality, such as SAE J1939 data logging and SAE J1939 simulation. Both features will be set up per the JCOM1939 Monitor software (definition of PGNs to be logged or simulated), and, with the flip of a DIP switch, the gateway will work independently from the PC connection.

At the time of this writing, we support only the gateway function as described above. We have a plethora of ideas for additional functionality, but, naturally, they will take time to accomplish. 

Yet, any firmware upgrade will be available as a free-of-charge download. Consequently, by buying the SAE J1939 Gateway Module With USB Port, RTC, MicroSD Memory Card you will receive firmware updates as soon as they are released.

For further information, please feel free to contact us. The board is fully tested, and we have sufficient inventory, but we are still working on firmware updates as described above. Furthermore, we are working on an optional enclosure. 

A Comprehensible Guide to J1939

SAE J1939 has become the accepted industry standard and the vehicle network technology of choice for off-highway machines in applications such as construction, material handling, and forestry machines. J1939 is a higher-layer protocol based on Controller Area Network (CAN Bus).

It provides serial data communications between microprocessor systems (also called Electronic Control Units - ECU) in any kind of heavy duty vehicles. The messages exchanged between these units can be data such as vehicle road speed, torque control message from the transmission to the engine, oil temperature, and many more.

The information in this book is based on two documents of the SAE J1939 Standards Collection: J1939/21 - Data Link Layer J1939/81 - Network Management A Comprehensible Guide to J1939 is the first work on J1939 besides the SAE J1939 standards collection.

It provides profound information on the J1939 message format and network management combined with a high level of readability.

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