Instrument Control (GPIB, Serial, VISA, IVI)

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Timeout error Visa read with Yudian controller 508P

Hello, I have designed a program for controlling and monitoring 3 of these controllers embedded into the furnace (see picture 1). Program interface looks like this (see picture 2). The operation behind it is that I have flat sequence structure, where first frame has event structure and enables to activate different buttons, then 3 frames with monitoring.vi inserted into case structures. So I can active them when I run specific zone. The problem is that after I launch for example 2 zones, after some period of proper monitoring I receive a timeout error from one of the monitoring.vi. However, the data package arrives later, so after that when another monitoring.vi asks for another package I have 20 bytes instead of 10 at port, and this monitoring.vi reads data from previous one and so on, it looks like zones have changed between each other. After this one error it works fine. I have tested it for 3 hours and received this error only ones, usually when I start furnace. 

Do you have any suggestions? May be my programming is not good. You can check screen of vi. See picture 3. Monitoring.vi - picture 4.

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Hi sergi22,

 

I have some questions about your system:

  • What specific timeout error codes are you seeing? Can you attach screenshots of those?
  • Did you develop this code or is it an example from the furnace manufacturer?
  • What is the model of the furnace?
  • Can you attach the code you are using or snippets of the monitoring.vi?
  • Had this behavior always occurred?

 

Thanks!

Erika
Technical Support Engineer
National Instruments
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Hello, thank you for your reply I have already sorted it out. The problem was that sometimes (very rarely) controller's feedback takes more time to arrive to port than it is specified in manual. So when Visa reads bytes from serial port it happens that there are less bytes then required and timeout error occurs. Solution was to wait until all bytes arrive to the port and read them.

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