It is not possible to directly set the bit timing registers. However, the corresponding parameters for NI-XNET can be changed to define custom baud rates.For more definitions on each of these parameters, please see your LabVIEW Help.
- Synch. Jump Width (SJW)
- Time Before Sample (TSEG)
- Time After Sample (TSEG2) and Bit Time Quantum)
Proceed with the following steps to set valid inputs for these parameters:
- Open Measurement & Automation Explorer, right-click the CAN port and select Properties.
- Select Advanced and click Baud Rate.
- Input your desired baud rate, in this example with have used 533.33 kilobaud.
Note: there are some values that are not possible to achieve. If you enter an invalid number, you will get a similar message to the one below, where xxx.yyy is the closest valid baud rate to value you entered.
Baud Rate will be changed to the nearest valid value (xxx.yyy kBaud)
- Click Create List, select one of the Bit Timing Registers that has been generated, and select Use.
- Your Port Properties window should look like the image found below. Take note of the SJW, TSEG, TSEG2, and Bit Time Quantum values found in the red square.
Note: The values above are +1 for SJW, TSEG1, and TSEG2, therefore for this example the corresponding values are: SJW = 0, TSEG2 = 6, and TSEG1 = 6.
- Place a BaudRate property node on your block diagram by going to the Measurement I/O pallete >XNET> Session Node. Once you have dropped down the node on the block diagram, click the section under XNET Session and a menu will appear. Navigate to Interface > BaudRate.
- Format the parameters noted in step 5 into a Hex representation (see Additional information if you are unsure what this means). In this example, the final BaudRate value would be 0x8066007D.
- Wire this value into the property node as follows.
Note: The constant above has been changed to Hex Display by right-clicking the constant and choosing
Display Format... then select
Hexadecimal.
Additional Information
Note: The 'Sampling Mode' is a parameter of NI CAN hardware. Changing this value will not affect the functionality of a XNET device.
The baud rate format in advanced mode is in Hex with the format 0x8ABCDDDD. Where A, B, C, and DDDD are defined as follows:
- A is the (Re-)Synchronization Jump Width (SJW).
- B is the Time Segment 2 (TSEG2), which is the time segment after the sample point
- C is the Time Segment 1 (TSEG1), which is the time segment before the sample point.
- DDDD is the bit time quantum. This is used to program the baud rate prescaler.
You can use the
NI-XNET Compatibility Library for NI-CAN to allow your NI-XNET device to appear in Measurement & Automation Explorer as both an NI-XNET and NI-CAN device as shown below:
