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Communication Issue with Varian V-70 Turbo Pump Controller

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Hey All,

 

As a prelude, this issue may likely not be VISA related so much as related to either my physical connections or my misunderstanding of the product datasheet. Any help would be appreciated, but I can also reach out to the manufacturer if needed.

 

I am trying to command a Varian V-70 Turbo Pump controller from my host Windows 10 PC via a USB to RS232 adapter cable. My software configuration is as follows:

  • NI VISA 19.0
  • LabVIEW 2017 SP1 f3

I have tried to communicate with this device in both LabVIEW and in a VISA test panel in NI MAX. In both cases, I get the classic timeout error:

Capture.PNG

 

Attached is the manual for the device. Pages 74 and 75 are of interest, as they outline the physical connections and communication setup in software. Below are two relevant snippets:

 

connections.PNGCommunication Port

 

messageformat.PNGCommand and Response

I have ensured my VISA session is configured with the correct format (baud rate, data and stop bits, parity) and have also tired timeouts of various lengths. In addition, I have followed the manuals instructions for ensuring the controller is in the proper mode to accept commands via RS232. Based on everything I have tried, the questions/thoughts I have are as follows:

 

Questions:

  1. Does the first image imply in any way that a USB to RS232 converter could cause issues? The phrase "The external cable (not supplied) between the host computer and the controller doesn’t require any crossed wires so that the signal are connected correctly." is confusing to me.
  2. If (1) is the case, maybe I actually need to be using NI Serial 19.0 with a RS232 cable instead of a USB to RS232 adapter?
  3. To me, image 2 implies the commands are literally just the characters "A, B, C..etc" I am not familiar with the concept of a CRC, but some googling has explained the concepts yet I am unsure how this affects how I format my actual messages.
  4. To build off of (3), do I need to be formatting my commands as Request + CRC or is the CRC handled by the nature of VISA and the setup of my VISA session?
  5. I am not familiar with USB RAW mode, but maybe I should be using that?

Articles used:

Error -1073807339 VISA Read or Write Timeout

How Can I Communicate With a Device Using NI-VISA USB RAW Mode?

 

Thanks for any help!

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  1. Does the first image imply in any way that a USB to RS232 converter could cause issues? The phrase "The external cable (not supplied) between the host computer and the controller doesn’t require any crossed wires so that the signal are connected correctly." is confusing to me.

A USB-RS232 adapter should be fine in this case. This phrase is just saying that you can use a standard, straight-through serial cable and you don't need a null modem (or crossover) serial cable.

 

  1. If (1) is the case, maybe I actually need to be using NI Serial 19.0 with a RS232 cable instead of a USB to RS232 adapter?

Whether you use a built-in serial port in your computer or the USB adapter, the results should be the same. That being said, I'd always suggest trying another port just as a troubleshooting step to rule out the adapter as the cause of the timeout. You could also try a serial loopback on the adapter just to make sure it is working correctly.

 

  1. To me, image 2 implies the commands are literally just the characters "A, B, C..etc" I am not familiar with the concept of a CRC, but some googling has explained the concepts yet I am unsure how this affects how I format my actual messages.

I'm struggling to understand this as well, whether you need to just send the character or need to send the full Request+CRC. You could try both! But I would also say that the manufacturer should be able to give you better explanation about how that commands should be formatted.

 

  1. To build off of (3), do I need to be formatting my commands as Request + CRC or is the CRC handled by the nature of VISA and the setup of my VISA session?

I don't believe that VISA will automatically handle the CRC. VISA should just be writing out whatever bytes you specify in the VISA write VI.

 

  1. I am not familiar with USB RAW mode, but maybe I should be using that?

USB RAW is used to control USB devices, but in this case the USB to serial adapter should be enumerated on your PC as a COM port. So you only need to communicate with the COM port using VISA and don't have to worry about the USB communication at all.

 

Jordan Calvert

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Thanks for your help, Jordan! I think the next step is try to a bunch of different command configurations and if all else fails contact the manufacturer.

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