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Why doesn't CloseCom release the com port for an .exe program launched through LaunchExecutable

During the middle of my test procedure I have to execute a program (tdy) that downloads to a Flash Ram, using RS232.
This application is written by a third party and its source code is unavailable to me. What I am trying to do up till
now is to open the com port using ... OpenComConfig(4, "COM4", 9600, 0, 8, 1, 512, -1); I do my normal
communications with the UUT. Close the com using...CloseCom (4);  Then I run LaunchExecutable ("tdy.exe");
(The tdy program also uses com4.) I get a time out error from tdy every time. If I run LaunchExecutable ("tdy.exe"); first
it will execute ok. Then when I OpenComConfig(4, "COM4", 9600, 0, 8, 1, 512, -1); I can comunicate with my UUT.
But this procedure is not practical due to the fact that at the end of test I use CloseCom (4);  which, of course, causes the same problem
on the next UUT.
I am using Windows2K, Labwindows CVI 6.0;
 
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Hi,

Can you post the NI-SPY capture for the two instances please.

Thanks,

Arjun K

National Instruments
Applications Engineer
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