CANopen Library concept
The CANopen Library is offered at different configuration levels. All configuration levels are built upon one another. The functionality of the lower level is contained in the higher one.
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The last criterion is the independence of the CANopen Library of the underlying hardware and operating system. It is easy to adapt the prepared driver modules to any target system. A further aim is to support a wide range of standard hardware products like CAN cards for PCs or micro controller modules.
Design flow
The CANopen Library is only one component in the design flow of the CANopen system development. The development of CANopen systems consists of the two tasks, implementation and integration. In the context of the CANopen Library the implementation task must always be done.
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The next step is the device integration into a CANopen network, creating a distributed application. It is very convenient to use a configuration tool. This tool loads the EDS-files of the participants (devices). Then the communication channels can be built by distribution of CAN-IDs and PDO mapping. Further the application parameters can be changed. Afterwards a so-called Device Configuration File (DCF) is stored. The configuration data can be downloaded onto a control application, which configures the network after each boot-up. Afterwards the configuration tool is no longer necessary within the CANopen network, it will only fulfill maintenance requirements. A summary of the complete tool-set is shown in Figure 12.
CANopen Library structure
The structure of the CANopen Library is shown in Figure 13. The CANopen Library consists of a hardware-dependent section and a hardware-independent section. The two sections are joined by message buffers (CAN receive and CAN transmit buffer).
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The structure is created this way, so that an update of the entire CANopen Library files is possible without modification of the application-specific code.
Object dictionary
The object dictionary is the data interface between the user’s application and the CANopen Library. It contains all variables that are necessary for the CANopen services and the application-specific variables that shall be accessible over the network. The implementation of the object dictionary by port consists of an array of element headers for each used index, see Figure 15.