Wolfgang Wallner, Bernecker & Rainer Industrie-Elektronik Ges.m.b.H., Austria
Dietmar Brucknerr, Bernecker & Rainer Industrie-Elektronik Ges.m.b.H., Austria
Josef Baumgartnerr, Bernecker & Rainer Industrie-Elektronik Ges.m.b.H., Austria

Applications in the domain of industrial automation often consist of multiple nodes running real-time critical tasks, linked together by a deterministic network solution to ensure predictable data exchange.

The openPOWERLINK stack is an open-source implementation of the deterministic real-time Ethernet network protocol POWERLINK, and together with RT PREEMPT Linux it provides application engineers with a powerful and flexible platform for their real-time solutions. At previous conferences, the openPOWERLINK stack has already been presented and described in variants implemented in Linux kernel-space and in user-space with all the according benefits and drawbacks. This paper introduces a new implementation approach that combines the flexibility of user-space application programming with the high performance of a kernel-space based solution. The openPOWERLINK stack has been split into a time critical part running as a Linux kernel module and a user-space library interacting with the real-time application. The kernel module directly accesses the Ethernet device via custom hardware drivers and runs the time critical POWERLINK Data Link Layer. The industrial control application is linked against the user-space library which implements all upper layers of the POWERLINK protocol such as SDO, object dictionary, or configuration management. Besides presenting the implementation steps, the performance of this new solution is examined regarding reachable network cycle times, jitter behaviour, and system load.

As an outlook, ideas are given to further optimize the openPOWERLINK implementation on the RT PREEMPT platform.