Hello,

Is there any way to know if a CAN message has been received on one of the CAN buses?

I would like to program the display to automatically recognize presence of a 2nd engine on the 2nd CAN bus. This bus will only be used if there is a second engine.

I think I can also look for a variable to remain invalid, just not sure how to implement that. If I were to use engine RPM for this purpose, what would be the result of "If Engine RPM > = 0...." If data is valid, value will always be >= 0, but if data is invalid would the IF be false? I've never used 'invalid' in this manner so I am not sure if it will work.

Any help is appreciated!

Regards,
Phil

Hi,

Sorry I see you have had no replies but I have a similar request, I want to show if an item is connected to the CAN.

You can test for if it has been connected then goes “off-line” but that does not work if the item is already “off-line” when you power up the screen.

Did you find a solution? or can anybody help.

Regards, Brian

Hi!

The IsValid() will tell you when a parameter is being received by a display.

For example, if the expression,
IsValid(J1939_Engine_Engine_Speed)
is executed as a condition to fire an event, you would see that the event will only occur when the J1939_Engine_Engine_Speed parameter is received by the display and for the period of time set to wait for the parameter to go invalid (Look on the variable, the Invalidate After: setting, default is 5 seconds).

You would probably use a timer to execute the condition.

Checking for the speed to be a value greater than 0 along with the IsValid() test is a good way to see if the engine is running. For example,
AND(IsValid(J1939_Engine_Engine_Speed), J1939_Engine_Engine_Speed > 500)
is commonly used.

Thank you!

Hi Sara,

Thanks!

In your example with engine speed, if its > 500 RPM doesn't that mean the data is valid? Or does the display hold the last valid value?

Phil

The variable holds the last data value. That's why the IsValid() is needed.

Hi Many thanks for the reply

I am using Studio 2.6 and cant find a ref to IsValid()

What is the syntax

I want to use this in a script to see if a free form CAN message exists I am getting error messages

If (messageok)
{

}

Error-ERR : Expression must be of boolean type
Error-ERR : No matching signatures to 'IsValid(bool)

Regards Brian

The IsValid is from a calculation event, to see if a variable is valid from a script, handle the return of smRead

It's not too clear in the documentation about this, but the scripting help file (in the PVCS) is good!

Josh