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Error 74 Unflattened From String for VISA Read

BLUF: I am getting Error 74: Unflatten From String: Memory or data structure corrupt. after trying to unflatten a string from VISA read.

 

Here is what I am doing. I have several data types in a message that I am flattening to a string and then writing to a serial port using VISA. I am using a loopback connector on my serial port to then read what I wrote using VISA read. I am able to read the message in binary, but I would like to unflatten the string and unbundle all of the data types and display each to test my serial transmission. The problem is that I am getting the error mentioned in my BLUF above when trying to do this. Does anyone know how to correct this issue?

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Message 1 of 16
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Hi Scaz,

 

check your string for completeness and correctness!

 

Otherwise give "good" and "bad" examples of your string conversion to let us check them…

Best regards,
GerdW

using LV2011SP1 + LV2017 (+LV2020 sometimes) on Win10+cRIO
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Message 2 of 16
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I am not sure what you are asking for. I always get ERROR 74 when I try to run the VI. I am wiring the Type connector on the Unflattened From String directly to my cluster of elements that I send to the Serial Write VI.

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Message 3 of 16
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Hi Scaz,

 

please provide a VI containing a string with data set to default and your conversion…

 

To say it the other way: when everything is set correctly the conversion will work without errors. As you get errors you (probably) did something wrong! But without any data/examples/VI we cannot check the source of the problem!

Best regards,
GerdW

using LV2011SP1 + LV2017 (+LV2020 sometimes) on Win10+cRIO
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Message 4 of 16
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I attached an example of what I am trying to do. This a simplified version of a portion of my code that is giving me problems. The unflatten from string is what is giving me errors. Any help would be appreciated. Thank you.

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Message 5 of 16
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Hi Scaz,

 

your VI doesn't contain any string with some value set to default - as I asked for…

 

But what I can say from your VI: using BytesAtPort is wrong for (atleast) 99% of all use cases! You need to make sure you read enough bytes so yoou can parse your string into the cluster you want it to be!

 

So again I ask you to provide an example VI with a string containing data you have received from your serial port, which gives errors in unflattening!

And while you're working on this: remove BytesAtPort from your VI. Either use a TermChar (which might be problematic with your binary data) or send/receive messages of known length!

Best regards,
GerdW

using LV2011SP1 + LV2017 (+LV2020 sometimes) on Win10+cRIO
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Message 6 of 16
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Compare 2 strings GerdW is asking for. (1 - sent, 2 - received). They should be _identical_. If not, conversion will fail.

Untill you receive identical strings, do not blame unflatten.vi

 

Check what is different between these 2 strings.

Different size, incomplete string?

Some bit order in your data makes LineFeed byte and transmission stops?

Etc...

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Message 7 of 16
(2,706 Views)

Maybe something like this would work better?


I'm using two ports and a null modem.

 

Unflatten String from Visa Read_BD.png

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Message 8 of 16
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What would be the best way to compare the sent and receive strings?

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Message 9 of 16
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The "Equals" function.

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Message 10 of 16
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