J1939, CANopen and the future for CAN

Anyone working with CANbus control will regularly come across other standards related to the technology: here, Morten Moller of Sensor-Technik UK takes a look.

In February 1986, Robert Bosch introduced the CAN serial bus system at the SAE congress in Detroit.

It was designed to handle short messages, support multi-master access, and offer a high degree of reliability.

In mid-1987, Intel delivered the first CAN chip, and today more than 20 chip manufacturers produce devices that offer CAN interfaces.

CAN quickly gained a dominant position among bus protocols.

In 1999 close to 60 million CAN controllers made their way into applications; more than 100 million CAN devices were sold in the year 2000.

A big advantage of the CAN bus compared with other network solutions is the price/performance ratio.

Price-wise, CAN is the most affordable network next to a regular serial channel.

With CAN being a pure datalink layer implementation, higher level application layers have been developed to increase CAN's suitability for use in specific areas of different applications.

As a real-time CAN solution for heavy duty applications, J1939 is suited for equipment used in industries ranging from agriculture, construction, and fire/rescue to forestry, materials handling, and on- and off-highway.

Communication systems designed according to J1939 standards are EMI/RFI tolerant, free of connection wires, easy to install, and feature log, record, remote access, and self- diagnosis capabilities.

The J1939 standards family is maintained to CANopen is a network technology optimised for use in industrial control environments, in machine internal networks and in embedded systems (any control unit deeply "embedded" in a device with electronics).

In industrial control terms CANopen is a "fieldbus".

Some fieldbus applications use derivations from RS485 for similar embedded networks.

However, with RS485 the network designer/developer needs to invent many communication routines.

CANopen, on the other hand, features a pre-defined set of network communication functionality.

Although the CAN protocol is now 15 years old, it is still being enhanced.

For example, at the beginning of 2000 an ISO task force involving a number of companies defined a protocol for the time-triggered transmission of CAN messages.

In addition, other standards are being formed to enable new items of equipment to be connected - for example allowing simple data transmission between new machinery and a tractor.

Also, different industries are generating their own specifications, increasing the scope of CAN as a universal interface.

Lots of manufacturers will tell you that their products are freely programmable, but what do they really mean?.

More often it means "freely programmable" but only with the software that they supply.

In effect, they're locking you into their products.

With Sensor-Technik's CANbus products, you can use whatever software best suits your needs - a standard programming language like C, or an IEC1131-3 compliant graphical program, including Function Block Diagram, Ladder Diagram, Instruction List, Structured Text or Sequential Function Chart.

That means you can buy products from many different manufacturers, but put your system together using a single software package.

Sensor-Technik offers an extensive function library of ready-to-use components, making it quick and simple to develop even complex applications.

Debug and diagnostic tools are also available on request.

Alternatively, Sensor-Technik can develop your complete software application for you.

Our freely programmable software is already approved by international standards and, used together with approved hardware, will save time and money associated with getting approvals after the project is completed, if that is even possible.

Safety standards are particularly important.

The safety standards authority TUV has already certified some of the proprietary CAN-based safety systems and the software used to program them.

CANopen-Safety is the first standardised CAN solution to earn a tentative BIA approval.

Also, approval of the CANopen framework for maritime applications by one of the leading classification societies worldwide - Germanischer Lloyd - is in preparation.

Many products in Sensor-Technik's range are also SAE J1939 compliant, and there is associated configuration software.

This simple to use software with familiar Windows interface allows generation and editing of user-specific graphics, text and pages.

It dramatically simplifies the generation of tables of variables, and of linking these to graphics and to real-world text messages.

It has been designed to be easy to learn and use so that you can be configuring your systems within minutes.

The editor has been equipped with a special WYSIWYG interface for the representation of the operating panel display.

This means that the character set of the device is presented on screen in exactly the way it will appear on the device.

The same applies to graphics, which are shown in exactly the way they will appear on the LCD.

To simplify data generation, different colours are assigned to individual functions.

Thus, the different entries can be easily identified on the display.

In configuration mode, the J1939 software provides views of the editor with J1939 connection, the table of variables, and the graphical representation of the connected equipment.

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