What problem with comunication?

[ha noi]

I'm using labview to communicate with hardware via RS232! But sometime, i can't received any data from hardware.Sometime it worked very well.

 But with other software(  not labview, suport from hardware's company) it works perfect, I alway can communicate with hardware!

When i got problem, i re-install labview, VISA, then it's work.....what is the problem?

[craigc]

Are you closing and opening the session correctly all the time.  This sometimes locks up when you try to open a refernce that is already open etc.

Craig 

[ha noi]

hi! I'm using the example in labview: "Basic Serial Write and Read.vi ". So i think there isn't any mistake with that vi. But I still got that problem!

[craigc]

Hi,

Will need a some more information to assist you further, What hardware is it?  What serial parameters does it use, flow control etc?  Have you modified the example "Serial Basic read and write.vi"?  is there an error associated before it locks up?

Craig

[ha noi]

The hardware is sensors. It's not difficult to communicate with computer! The commands are simple! I tried with the basic "Basic Serial Write and Read.vi ". sometime it's work good, but sometime i can't not communicate! I didn't change anythings!

I used NI spy see the communication! I attach the picture, maybe you get some solutions for me! Thanks

[ha noi]

I upload new picture! I hope it's better than prevouis pic!

[ha noi]

I test with Hyper Terminal, it works correctly!

[CDancer]

Just a thought - could it be connected with termination characters?

For example, when you type Enter in a Labvew string control you get a line feed character, so I think that is what the basic serial I/O vi will be sending out to your instrument, but perhaps your instrument is expecting a carriage return or CR/LF pair?

[craigc]

Hi,

From the NI Spy log, it looks like when it fails there are no bytes at the serial port when you get a fail.  This suggests that the write command is not being sent properly, or the hardware has not replied.  Since it sounds like the hardware works correctly with hyper terminal it looks like a comms setup problem.  As suggested, have you ensured you are sending the correct Termination characters?  Is the parity / Flow control setup as dictated by the hardware?  Without looking at your vi and knowing what the hardware requires it is a little tricky to pin down the problem.  Serial control can be very picky when it wants to be.

Craig

[ha noi]

I tried to test something, but i still can not find the problem!

In Hyper terminal, i typed any commands ( you can see in the picture), i always got respones from hardware!

But i tried with labview, sometime it worked, sometime did not work.

Some one can explain for me the different between " VISA Write ("COM3", "MOIST?0..") "  and "" VISA Write ("COM3", "MOIST?0") ". If after the command ( in NI spy ) , there are" .. " , I always gets the communication,.