VISA error

[__dave__]

Hello.

I have communication problems while trying to initialize an instrument (Norma 4000).

There's something weird : if i use the windows hyperterminal, I get the expected answers from the instrument.

But as soon as I try to send the same commands using visa (LabWindows/CVI, LabVIEW or MAX), I get unexpected characters.

Here is an example of what I got with LabVIEW :

Requête:31/05/2012 15:33:05.81064 (+10.1563 seconds)

*RST.*IDN?.

Réponse:31/05/2012 15:33:05.81064 (+0.0000 seconds)

@øLEM,NORMA 4000,UO13246BA,V1.2

instead of :

Réponse:31/05/2012 15:33:05.81064 (+0.0000 seconds)

LEM,NORMA 4000,UO13246BA,V1.2

Does anyone have a solution ?

Thanks in advance

Dave

[smercurio_fc]

Are you programming this yourself, or are you using the drivers: http://sine.ni.com/apps/utf8/niid_web_display.download_page?p_id_guid=BA0B4F7903CF0566E0440021287E65...

[__dave__]

No no, I'm using the NI MAX tool (Measurement & Automation) and the hyperterminal.

And I forgot to specify that I'm using the serial port to communicate with my instrument.

[nyc_(is_out_of_here)]

---

@__dave__ wrote:

No no, I'm using the NI MAX tool (Measurement & Automation) and the hyperterminal.

And I forgot to specify that I'm using the serial port to communicate with my instrument.

---

That's not what he is asking.

He is asking when you are using LabVIEW whether you are using the LabVIEW driver.

[__dave__]

Ah ok.

I have tried to communicate with the Visa vis provided with LabVIEW.

[smercurio_fc]

I'm not overly surprised at seeing some "garbage" characters occur after a *RST command. HyperTerminal hides most non-printable characters so you think they're not there, but they actually are. You could try clearing the buffer after a reset.

But then, as I noted, there's a driver for that instrument, so why don't you use that?

[__dave__]

I cannot use the driver you advise me because this driver is for GPIB.

And I'm trying to repair the communication through RS232.

How can I clear the buffer ?

[smercurio_fc]

Actually, the driver uses VISA. Consequently, it wouldn't take much to have it handle a serial interface. Many of the drivers on the NI site that use VISA are written to work with either GPIB or serial. If you look at the 34401 driver that ships with LabVIEW you will see how it's handled in the Initialize VI.

As for clearing the buffer, there's a VISA function for that: VISA Flush I/O Buffer. It's in the VISA -> Advanced -> Bus Specific palette. Please refer to the LabVIEW Help on how to use it.

[__dave__]

I've tried the given driver.

I get the same problem : I receive weird chars, which make the initialization fail.

[smercurio_fc]

As you indicated and I confirmed, the driver was written to work with a GPIB interface, so I'm not sure I understand what you did when you said you tried the driver. Unless you made modifications so that it would configure the serial port, the driver would probably not work with a serial interface.

I would suggest that you monitor the serial port to see if these extra characters are coming when you use HyperTerminal. If you're on Windows, the PortMon utility (available from Microsoft) can be used to capture the serial port. You can then see if you're actually getting these when you use HyperTerminal, and if HyperTerminal is simply hiding them.

[__dave__]

As I said in my first message, I've tired to monitor the instrument with the windows hyperterminal, and there wasn't any additional character.

Then I tried to monitor the instrument with NI Max (using VISA), and the unexpected characters occured.

See the 2 attached files (one for the hyperterminal, and the other for MAX)

[smercurio_fc]

HyperTerminal is not a monitoring program. You also do not monitor using MAX. To monitor you need something else, which is why I suggested PortMon, which allows you to see explicitly the bytes that are sent over the serial port. NI-Spy will do this as well, but it won't work with HyperTerminal. You chose to use HDD Software Serial Monitor, which is fine. Of course, your screenshots show no difference between the communication done with HyperTerminal and the communication done with MAX. Both show the same exact response to the *IDN? command.

[__dave__]

Yes, you're right, I get the same answer to my "*IDN?"

But if you look at the next command, you will see the problem (see attached file)

[smercurio_fc]

Something doesn't look right with those captures. And by that I don't mean the received data. I'm referring to the timestamps. In the one for HyperTerminal the response from *RST *IDN? comes about 150 msec after the command. In the MAX case it comes 10.6 seconds later. This makes no sense to me. Additionally, the HyperTerminal capture shows the second set of command being split, with a 12 second gap. The MAX command set was sent 15 seconds after the response from *IDN? and the response coming 2.5 seconds later.

How exactly are you sending these commands in MAX? And how are you sending these commands in HyperTerminal? Are you uploading a file with the command in there?

You said you tried to do this in LabWindows and LabVIEW. Can you upload your actual code?