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Defining Initialization and Termination CAN Messages
The CAN Setup driver blocks for all supported CAN boards allow the definition of CAN-messages to be sent out during initialization and termination of the target application (once at the beginning of each application run and once before an application run is stopped). The main purpose for sending out those messages is to initialize or terminate other CAN nodes on the network. This is for example the case for CANOpen or DeviceNet nodes. Even if xPC Target doesn't provide direct support of those CAN application layers, communication with those nodes can usually be done over `standard' CAN messages as long as the nodes have been properly initialized. The initialization and termination fields of the Setup blocks are intended for this purpose.
The initialization and termination CAN-messages are defined by using MATLAB struct arrays with CAN specific field names. This is the same concept as used for the RS-232, GPIB and general Counter driver blocks found in the xPC Target I/O library. Refer to those driver blocks and their help for additional information about this basic concept.
The CAN Setup block specific field names are the following.
Port -- Selects the CAN port over which the message has to be sent out. Valid values are either 1 or 2 (double).
Type -- Defines if the message to be sent out is of type Standard or Extended. Valid values are either `Standard' or `Extended' (strings).
Identifier -- Defines the identifier of the message. The value (scalar) itself has to be in the corresponding identifier range (Standard or Extended).
Data -- Defines the data frame to be sent out along with the CAN message. The value has to be a row vector of type double with a maximum length of 8. Each element of the vector defines one byte, where the first element defines the data for byte 0 and the eight's element the data for byte 7. Each element can have a value between 0 and 255 (decimal). The data frame size is defined by the length of the row vector.
Pause -- Defines the amount of time in seconds the Setup block waits after this message has been sent out and before the next message defined in the struct array is parsed and sent out as well. Valid values are in between 0 and 0.05 seconds. Some CAN nodes need some time to settle before they can accept the next message, especially when the just received message puts the node in a new operational mode. Use this field to define those necessary idle times.
| | CAN-AC2-104 (PC/104) | Example | |