Embedded Networking with CANopen
By Olaf Pfeiffer
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Implementing CANopen
CANopen can be implemented on almost any microcontroller with an on-chip or external CAN interface. If the maximum bus speed of 1Mbps needs to be supported, the minimum requirement would be an 8-bit controller leaning towards the higher end on the performance scale. Concerning CAN interfaces, it helps to have one of the smarter ones that either have a large amount of receive buffers or a true FIFO buffer. The latter greatly improves the timing requirements by giving a microcontroller up to 10 times more time to react upon a CAN interrupt.
CANopen protocol stacks written in C are commercially available from a variety of vendors and are already adapted to a wide variety of microcontrollers and CAN controllers. They are usually all available with source code for a one-time fee, no royalty or license fees required.
There are also the first CANopen chips available, which implement the entire CANopen protocol stack in a single chip that can directly integrate digital and analog I/O into a CANopen network.
When it comes to debugging a CANopen system, there are a variety of tools available to ease debugging. Just to name a few, we have protocol analyzers that can receive, log and transmit CANopen messages. There are also configuration tools, which can scan a network for all connected nodes and tries to match them up with EDS files allowing displaying and modifying all the supported Object Dictionary entries of the connected nodes.
A detailed list of vendors offering CANopen products can be found on the web pages of the CiA, the CAN in Automation user's group: www.can-cia.org.
Olaf Pfeiffer is one of the founders of the Embedded Systems Academy. He studied technical computer science at the Co-Operative University in Karlsruhe, Germany. His dissertation about embedded networking with field busses won the award of best dissertation of the year. He continuously conducts training classes and publishes articles and on-line documents about different microcontroller architectures, embedded networking with CAN and CANopen and Embedded Internetworking. A free on-line training class on Embedded Internetworking and other related topics are available from the web pages of the Embedded Systems Academy at www.esacademy.com
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