J1939 References...
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Application of
J1939 Networks in Agricultural Equipment
The critical need for a
standardized electronics communication protocol for agricultural
equipment was recognized as early as 1986 at ASAE (Bernard, 1986).
In-vehicle networks were being developed earlier for on-highway systems
and included the Society of Automotive Engineers (SAE) recommended
practices J1708 and then J1587 in on-highway trucks and J1850 in
automotive applications. J1587 is currently being used in both truck and
bus and construction equipment applications (Luebbering and Smith,
1993). J1587 is currently in use in agricultural equipment and may be
the earliest standardized in-vehicle network used in these applications.
Focused efforts by the US construction and agricultural equipment
industry to participate in development of a US and an International
standard were begun in December 1992. Earlier that summer, the first
meeting of the International Standards Organization working group for
mobile agricultural electronics, ISO/TC23/SC19/WG1, was held and focused
on development of an interim standard for communication between tractor
and implement. The initial work defined a connector with frequency and
analog based signals. In addition, a proposal based on a developing DIN
standard was presented by the German experts. The ISO activity
instigated action by the US industry and by summer of 1992, a US
proposal was added to proposals from Germany and the UK at the ISO
working group (Stone and Zachos, 1992). The CAN (Controller Area
Network) 2.0b (Bosch, 1991) based SAE J1939, an SAE draft recommended
practice for heavy-duty vehicle networks, has now been endorsed by the
Joint ASAE and SAE committees responsible for developing network
protocol standards for agricultural and construction equipment (ASAE IET
353/1 and SAE ORMTC/SC32 - Off Road Machinery Technical
Committee/Electronic Control and Monitoring Systems). Currently the
network protocol work has evolved and the ISO working group has adopted
SAE J1939 as a working document. Provisions for construction and
agricultural equipment have been added to SAE J1939. Some of the
fundamental components of J1939 have been balloted and approved. Other
fundamental components are expected to be approved in early 1994. The
construction and agriculture components of J1939 are still in draft form
as are the network management and diagnostics components.
J1939-based application profiles
On calculating guaranteed message
response times on the SAE J1939 bus
Since it’s introduction in 1995
the SAE J1939 protocol has become a ‘de facto’ standard for heavy truck
manufacturers throughout the world. The recommendation has several
benefits; at first, it constitutes a common interface between different
control units, supplied by different vendors, on the same bus. Secondly,
it provides detailed information about signals (entities) that are
communicated on the bus. Thirdly, the recommendations, if accepted and
adopted as a real standard, may reveal vendors from the
difficulties of certification when used in safety critical applications.
The background of this report is part wise the authors experiences
gained from coop project with Volvo Truck Corporation in Sweden (VTC)
but also a result of joint projects with Saab-Ericsson Space (earlier:
Saab Space) and Volvo Car Corporation (VCC). An essential part of
chapter 4 is based on earlier published material.
Read more... (PDF)
Dynamic Address Configuration
in SAE J1939
Electronic components have
become common on agricultural and construction equipment as equipment
manufacturers have attempted to build more functionality and efficiency
into their products. A natural consequence of the proliferation of
electronic components has been the development of multiplexed
communications networks on-board the equipment. These networks allow
communication between multiple electronic control units (ECUs) over
multiplexed or shared communications wiring. Multiplexing simplifies
wiring and lowers total system costs while providing a means to share
sensor values and other data. On the other hand, multiplexing increases
the complexity of the electronics systems, as some technique must be
implemented for controlling access by each of the ECUs to the shared
wiring. A further complication is the need for ECUs to have some means
of unique identity on the shared network.Efforts by agricultural and
construction equipment manufacturers to control product costs have also
affected development of multiplexed wiring systems. Higher volumes of
electronic components reduce cost and have driven standardization of
multiplexed wiring systems. The construction and agricultural equipment
industry initiated standards development for multiplexed wiring in 1990
in conjunction with the establishment of the ISO TC23/SC19WG1.
