Field buses are widely applied in the control of mobile machines. They enable us to build embedded control systems, where the sensors and actuators are connected to each other by the bus. The most commonly used bus standard for Control Area Network (CAN) between tractors and implements in agriculture and forestry is ISOBUS. Once the number of sensors and actuators increases in the implement side, a combination of ISOBUS and CANopen can be applied. CANopen is a communication protocol and device profile specification for embedded systems used in automation. In addition to agricultural applications, it is used in mobile machinery in mines and forestry, in power systems such as substation automation and wind turbines, and in many other kinds of industrial systems, which require embedded automation to be able to operate. However, there are always places which are not reachable by cables. These parts can be mobile, or the mechanical conditions can otherwise be too harsh for the cables.  A wireless extension of CANopen enables us to connect these parts to the CAN-based control system. It will also enable us to connect several mobile machines to the same control network.

In this paper we present the implementation of CANopen protocol to wireless sensor platform called the UWASA Node. The UWASA Node is a modular and stackable wireless sensor node, which is designed to fill the requirements of wireless automation. There are enough memory and computation power to run some computation required by the control applications in the node. The modular hardware architecture and the protocol software architecture enable a relatively easy integration of different kinds of industrial sensors depending on the measurement needs. On the other hand, the UWASA Node can operate just as a low energy consuming router in a mesh type of network, if such architectural solution is preferred.   The CANopen implementation to UWASA Node is done by using the open source stack CanFestival. It is tested by a set of standard CANopen functionality tests in cooperation with TK-Engineering Ltd. and CANopen competence center C3 Vaasa. Certain errors and operational shortages are detected and fixed based on the test results. Finally, the hybrid control system consisting of CANopen fieldbus and the wireless sensor network is tested and its performance in terms of capability and reliability is evaluated based on the test results. In the conclusions we also evaluate the feasibility and possible limitations of CanFestival compared to some other CANopen protocol stacks.