VCI - Virtual CAN Interface - Ixxat

Accessing the bus3 Accessing the bus3.1 Accessing the CAN bus3.1.1 OverviewIn the following, a typical CAN interface board with two connections for CAN 1and CAN 2 is shown.IXXAT interface boardCAN controller 1CAN controller 2Control unitCyclic transmitlist (optional)MessagechannelCAN 1 CAN 2Fig. 3-1: CAN interface board with two CAN connections.In addition to the CAN connections, a CAN interface board can also have othertypes of bus connections. However, these are not relevant in the following.As shown in Fig. 3-1 for connection 1, each CAN connection consists of up tothree different components. A control unit, one or more message channels andwhere appropriate a cyclic transmit list. The control unit and the message channelsare always available. The cyclic transmit list is only normally found with CANinterface boards that have their own microprocessor.The control unit of a CAN connection is accessed with the function canControlOpen.The function canChannelOpen opens a message channel and the functioncanSchedulerOpen access to the cyclic transmit list of the connection.All three functions expect in the first parameter the handle of the CAN interfaceboard and in the second parameter the number of the CAN connection. For connection1, the number 0 is allocated, for connection 2 number 1 and so on.To save system resources, the handle of the CAN interface board can be releasedagain after opening a component. For further accesses to the connection, onlythe handle of the component is required.The functions canControlOpen, canChannelOpen and canSchedulerOpen can becalled so that the user is presented with a dialog window to select the CAN interfaceboard and the CAN connection. It is accessed by entering the value0xFFFFFFFF for the connection number. In this case, instead of the handle of theCAN interface board, the functions expect in the first parameter the handle of thehigher order window (parent), or the value ZERO if no higher order window isavailable.14Copyright IXXAT Automation GmbH C-API Programming Manual, Version 1.5