Hi. I was wondering what the message valid output signifies. That is to say, is it a simple “there is a message here and it can be read” , does it signify the message has been received and checked for integrity, or is it something else entirely?
For context I am trying to implement a system that ensures messages are making it across an interface in one piece and am wondering if “message valid” output is a good enough indicator that the message arrived intact or if I need to implement further error checking.
Can you provide a little more context, such as when and from what are receiving this message?
Sorry, yes. We are sending CAN messages of randomized data through a slip ring. Currently messages are sent from controller 1 to controller 2 on the same USB CAN device. If a message is received “valid” then controller 2 sends a message back to controller 1. Messages are sent as constantly (every few milliseconds) while spinning the slipring. The goal is see how long before wear on the slip ring starts to effect CAN data transmission.
The LabView API is implemented with the same parameters and return values for each function as the VCI C-API:
4.02.0250.20012 C-API V1.5.pdf (803.7 KB)
Usually LabView VI according to the LabView concept uses only the return value “0” as the successful return value.
In the VCI C-API and LabView API though, “0” is not the only successfull return value.
For example, the function canChannelReadMessage can return the VCI_OK or VCI_E_TIMEOUT. LabView interprets the VCI_E_TIMEOUT as an error because it is not equal “0”, but it is not really an error - it just means that within the set time out time no CAN messages was received.
This is the origin for the valid output. If the valid output is true, then a message was successfully received.
But please note, that your LabView Application should check the type of the received message, because there are CAN messages of type Data, Remote Frames, and Error Frames and there are INFO messages like Timer Overrun.
Please see the attached VCI C-API manual and the C-API programming example for a better understanding.
cancon.zip (28.7 KB)
Thank you for the response, that does help clear things up.
You’re welcome! Please let us know if you have any other questions.