NI-VCOM provides additional functions, such as baud rate modification and bus load measurement.

Modify CAN/CAN-FD Baud Rate at Run Time

For CAN ports, you can change the defined baud rate, even at run time, using the BaudRate signal. To make the BaudRate signal visible in the NI-VCOM signal tree, configure the Change BaudRate tag in the NI:VCOM configuration tool to the corresponding restbus simulation peer. Then, set its value to true.

When dealing with instruments that support CAN-FD, there is an additional tag available called Change-BaudRateFD. When the value of Change-BaudRateFD is true, the DataBaudRate signal is visible in the NI-VCOM signal tree.

Bus Load Measurement

You can use NI-VCOM to measure the bus load of CAN instruments.

Set EnableBusLoad to true to enable the bus load measurement. Bus measurements are only an approximation and can differ from the real value. For CAN, a new signal called Busload is available, which shows the percentage of the load.

Bus State

  • CommunicationState—Communicates state.
  • LastError—Specifies the status of the last attempt to receive or transmit a frame.
  • RxErrorCount—Counts Rx errors.
  • Sleep—Indicates whether the transceiver and communication controller are in their sleep state. False indicates normal operation (awake) and true indicates sleep.
  • TotalErrorFrames—Counts error frames since the start of the bus.
  • TransceiverError—Indicates whether an error condition exists on the physical transceiver. This is typically referred to as the transceiver chip NERR pin. False indicates normal operation (no error), and true indicates an error.
  • TxErrorCount—Counts Tx errors.
    • Figure 14. Example Bus State After Disconnecting the Loop Between Two CAN Ports