Reads data from a session as an array of CAN frames. The session must use a CAN interface and a mode of Frame Input Stream, Frame Input Queued, or Frame Input Single-Point.


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Inputs/Outputs

  • cgenclassrntag.png session in —

    session in is the session to read. This session is selected from the LabVIEW project or returned from the XNET Create Session VI. The session mode must be Frame Input Stream, Frame Input Queued, or Frame Input Single-Point.

  • ci32.png number to read (-1) —

    number to read is the number of frame values desired. If number to read is positive (or 0), the data array size is no greater than this number. If number to read is negative (typically –1), all available frame values are returned. If number to read is negative, you must use timeout of 0. This input is optional. The default value is –1. If the session mode is Frame Input Single-Point, set number to read to either –1 or the number of frames in the sessions list. This ensures that the XNET Read (Frame CAN) VI can return the current value of all session frames.

  • cdbl.png timeout (0) —

    timeout is the time to wait for number to read frame values to become available. The timeout is a LabVIEW relative time, represented as 64-bit floating-point in units of seconds. If timeout is positive, the XNET Read (Frame CAN) VI waits for number to read frame values, then returns that number. If the values do not arrive prior to the timeout, an error is returned. If timeout is negative, the XNET Read (Frame CAN) VI waits indefinitely for number to read frame values. If timeout is zero, the XNET Read (Frame CAN) VI does not wait and immediately returns all available frame values up to the limit number to read specifies. This input is optional. The default value is 0.0. If the session mode is Frame Input Single-Point, you must leave timeout unwired (0.0). Because this mode reads the most recent value of each frame, timeout does not apply.

  • cerrcodeclst.png error in (no error) —

    The error in cluster can accept error information wired from VIs previously called. Use this information to decide if any functionality should be bypassed in the event of errors from other VIs. The pop-up option Explain Error (or Explain Warning) gives more information about the error displayed.

  • igenclassrntag.png session out —

    session out is the same as session in, provided for use with subsequent VIs.

  • i1dcclst.png data —

    data returns an array of LabVIEW clusters. Each array element corresponds to a frame the session receives. For a Frame Input Single-Point session mode, the order of frames in the array corresponds to the order in the session list. The elements of each cluster are specific to the CAN protocol. The cluster elements are:

  • iatrn.png timestamp —

    timestamp represents the absolute time when the XNET interface received the frame (sampled the Ack bit), accurate to microseconds. The timestamp uses the LabVIEW absolute timestamp type.

  • i1du8.png payload —

    payload is the array of data bytes for the CAN data frame. The array size indicates the received frame value payload length. According to the CAN protocol, this payload length range is 0–8. For CAN FD, the range can be 0–8, 12, 16, 20, 24, 32, 48, or 64. For a received remote frame (type of CAN Remote), the payload length in the frame value specifies the number of payload bytes requested. This payload length is provided to your application by filling payload with the requested number of bytes. Your application can use the payload array size, but you must ignore the actual values in the payload bytes.

  • iu32.png identifier —

    identifier is the CAN frame arbitration identifier. If extended? Is false, the identifier uses standard format, so 11 bits of this identifier are valid. If extended? Is true, the identifier uses extended format, so 29 bits of this identifier are valid.

  • iu8.png type —

    type is the frame type (decimal value in parentheses):

  • ibool.png extended? —

    extended? is a Boolean value that determines whether the identifier uses extended format (true) or standard format (false).

  • ibool.png echo? —

    echo? is a Boolean value that determines whether the frame was an echo of a successful transmit (true), or received from the network (false). This value is true only when you enable echo of transmitted frames by setting the XNET Session Interface:Echo Transmit? property to True.

  • ierrcodeclst.png error out —

    The error out cluster passes error or warning information out of a VI to be used by other VIs. The pop-up option Explain Error (or Explain Warning) gives more information about the error displayed.

  • i1dcclst.png unused payloads —

    payload is the array of data bytes for the CAN data frame. The array size indicates the received frame value payload length. According to the CAN protocol, this payload length range is 0–8. For CAN FD, the range can be 0–8, 12, 16, 20, 24, 32, 48, or 64. For a received remote frame (type of CAN Remote), the payload length in the frame value specifies the number of payload bytes requested. This payload length is provided to your application by filling payload with the requested number of bytes. Your application can use the payload array size, but you must ignore the actual values in the payload bytes.

  • i1du8.png payload —

    payload is the array of data bytes for the CAN data frame. The array size indicates the received frame value payload length. According to the CAN protocol, this payload length range is 0–8. For CAN FD, the range can be 0–8, 12, 16, 20, 24, 32, 48, or 64. For a received remote frame (type of CAN Remote), the payload length in the frame value specifies the number of payload bytes requested. This payload length is provided to your application by filling payload with the requested number of bytes. Your application can use the payload array size, but you must ignore the actual values in the payload bytes.

    • Description

    The data represents an array of CAN frames. Each CAN frame uses a LabVIEW cluster with CAN-specific elements.

    The CAN frames are associated to the session's list of frames as follows:

    Due to issues with LabVIEW memory allocation for clusters with an array, this XNET Read VI instance can introduce jitter to a high-priority loop on LabVIEW Real-Time (RT). The XNET Read (Frame Raw) VI instance provides optimal performance for high-priority loops.