RS232 Low Voltage...

[Istvan49]

Windows Hyperterminal was a good Idea! It works perfectly, even with the NI card... So what does that means? I have some progress to do with Labview? What is different? I put exactly the same parameters: 9600bds  8bits  no parity    stop=2    Xon/Xoff... I did exactly the same in the Serial configuration with the "Instrument I/O assistant"... But it doesn't work.

[K C]

I was focused on the low voltage. Like I said it's not good but it can work.

Did you set the termination character as it shoul like The Kid said.

Can you post the (basic) VI ?

[Istvan49]

Yes sorry, I was sure it was because of the low voltage (witch is still strange for me but..).

But I am not using yet a VI because i wanted to try the connection before. So I use the "Instrument I/O Assistant" in the bloc diagram of an empty VI. Then I set up all the parameters (speed, termination character...) and I try to send a command in the serial toolbox. But nothing... Just the famous "?" sometimes...

In the hyperterminal, no problem, after all the commands I receive the good answer. I don't understand what can be THE difference in the Labview assistant...

[K C]

It's OK, the low voltage is still a problem even if it is working. it will get back to you tomorrow, next month, next year

You said: 'So I use the "Instrument I/O Assistant" in the bloc diagram ' to be honest I don't know this assistant never used it. 

I can make you a basic COM VI which you can use to test your device communication.

[Istvan49]

If you have the time, yes you can make a VI. But I also tried a very basic one from this website (but not able to find it again...) and I had the same problem... But I will wait for your VI and will see...

Thank you again!

[K C]

OK, maybe later this evening or otherwise tomorrow morning (for me) I don't know where you are located ?

[K C]

I used a VI from a other RS232 thread.

This VI was ment to be used in a program. The configure and close should be at the beginning and end of a bigger program.

For the test I put the configure in front of this VI and forgetting the close

Default settings: Time-out is set 10 sec. and there is a <cr> added to the input string. You can change both.

Fill in your COM parameters if they are not correct.

Have a try and just ask if it's not working or something is not clear.

[Istvan49]

OK it is working... But what is this <cr> that you added? What is it for? Is it a kind of start message?

And for the low voltage: I didn't find any electrical specifications about my NI board... So Does anybody know if that's normal or if I have to change it, or to activate a power somewhere in the computer?

@KC: Thank you again very much for your help. I don't know why this "Instrument assistant" is not working, but your VI looks good.

[K C]

The <cr> is a ascii 'Carriage return' with most ascii commands you need to add this at the end of your command to a device to indicate the end of a command. The VI does this for you if you set the boolean input to (the default value) true

According to the spec. the PCI8430/8 only needs +5VDC for supply.

[JasonSmith]

The transceivers used on this serial board are designed to output at +/- 5V.  This meets the requirement of the RS-232 specification, and should not cause any trouble communicating with your device.

I am glad to hear that you have solved the problem communicating with your instrument.  I just wanted to clarify that the voltage levels you are seeing are normal and expected for this board.

Jason Smith
National Instruments