How to read the response available 3s later after issue command on the COM port (to solve the Error -1073807339) ?

[BigDrum]

Hello Everyone!

I am communicating with a device through COM port. That device response (1 byte to read) to command right away (<0.5s?) for all of the commands except one. That special command will take 3s to execute on the device then generate response back on the COM port. So when I use "VISA read" it error -1073807339 Timeout expired before operation complete. 

I added 5s wait after send the command and before reading the response, but still same error.

I tried pause 5s after send the command then read the response, but still same error.

So how to code to get the response of this special command? Thank you!

[crossrulz]

What device are you trying to talk with? Could you share more of your code that shows the full communication scheme you are using?

[daveTW]

So, are you sure there is an answer after 3 seconds? How did you prove it?

Did you set a terminator? If so, this would cause problems with a 1-byte response.

To debug your problem, this time it is useful to make a loop (with a small wait timeout) with a bytes-at-port node, to control whether there is a response at all.

[RTSLVU]

I would have to agree with crossrulz here, more information is needed on your device and its communication protocol.

NI-VISA timeout defaults to 2 seconds (2000mS) have you tried increasing that to 3 or 4 seconds?

[BigDrum]

The device is a communication module with ASIC. I am just using the common VISA vi from NI. The problem is all of the other commands work fine except this one which take 3s to response on the COM. 

[BigDrum]

Yes, I had used RealTerm to send the command and watch the response.

No, I did not set a terminator.

Yes, I can use Bytes at Port node to debug, thank you !

[BigDrum]

Yes, I can set the timeout = 4s like below. Thank you !

[billko]

I'd do it like this to preserve the original timeout value:

[crossrulz]

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@RTSLVU wrote:

NI-VISA timeout defaults to 2 seconds (2000mS) have you tried increasing that to 3 or 4 seconds?

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If using the VISA Configure Serial Port, the default is 10 seconds.

[crossrulz]

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@BigDrum wrote:

Yes, I had used RealTerm to send the command and watch the response.

No, I did not set a terminator.

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My guess is that you are not sending the termination character with this command, so the ASIC does not know the command has been fully transmitted.