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Digital Output Issues

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Hello Everybody,

 

I've been trying to code a subroutine that produces a TTL trigger signal. When I had it in test vi, which is smaller then then one I need to insert to, everything worked fine. After I inserted this subroutine into an original program I got the following message:

 

"Error -200429 occurred at DAQmx Write (Digital Bool 1Line 1Point).vi:3

Possible reason(s):

Measurements: Value passed to the Task/Channels In control is an empty string (or I/O control).

The value must refer to a valid task or valid channels."

 

I tried to understand the reason  why I am getting this message, but apparently with no luck.

 

 

The way how program should work is as follows, I created a case structure inside while loop to be able to gather data either manually or automatically.

 

 

For <<manual>> case, I placed a switch that should turn on trigger along with "write to file" option, that record data from load cell/motors.

 

For <<automatic>> case I wanted to create a threshold, passing which turns on <<trigger along with "write to file">>, otherwise do nothing.

 

I have a feeling that there is some logical error and I am not completely following how data flows should be organized in the presence of multiple structures.

 

 

I hope somebody with  a good eye on such problems can give a hand.

 

Thanks in advance

 

Oleks

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Solution
Accepted by topic author Oleks
You clear the task on the first iteration of the do-while loop. Place the DAQmx Clear Task outside the while loop. Have a look at the examples shipped with LabVIEW.
Adnan Zafar
Certified LabVIEW Architect
Coleman Technologies
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Thanks Adnan,

 

Thats was the problem I had. In the test program I had "Clear Task" outside of the loop, but when I start putting everything togather I guess I was not very careful.

 

Thank you again for the help!

 

Oleks

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