I get different responses when sending a GPIB command via VISA Write VI and MAX

[FlorianJ]

Hello community!

I'm programming a driver for the Advantest TR6143. Everything is working just fine, exept for onething. When I type a command in MAX, i get the desired Value change. When I enter another Value, it changes.

Let me give you an example:

1.)EV4D11.000MAD3.000

2.)EV5D11.000MAD4.000

1.)

E              output enable

V4            Voltage range up to 3.2 Volts

11.000MA current is restricted to 11 mA

3.000        3 Volts

2.)

since the Voltage now exeeds 3.2 V i need to go to a higher Voltage range.

I have a resistor at the output and Meassure the Voltage with a Scope.

All of this works perfect!

But now, when running my VI and canging the Voltage from 3V to 4V the exact same commands are sent via VISA Write, i checked with a probe. However, i get a Voltage peak before it changes to 4 Volts. This is a known issue with the Advantest source, and I think i can figure out how to avoid it.

My question is, why do I get different results by sending the commands via VISA and MAX?

Thank you for some clerification.

Florian

[Dennis_Knutson]

No idea why there would be a difference. I'm assuming you are not using the VISA Interactive tool in MAX and are instead using ibwrt and ibrd. Get an NI-Spy capture of both and attach

[Makoto]

When you send a command from VISA Write function, did you send termination codes such as CRLF or LF?

[FlorianJ]

Hello Dennis Knutson,

I'm using the NI-488.2 Communicator. I never used NI-Spy, I'll try to get the aptures then post them here.

[FlorianJ]

Hello Makoto,

I didn't use any termination code. Are CRLF and LF termination codes used by Advantest? I couldn't find anythin in the manual.

[FlorianJ]

Hi Dennis Knutson,

Here is the spy report attached. The first 3 Linse are produced using MAX, the rest of the lines shows the output using my driver.

[Makoto]

In NI-SPY log, your VISA Write call looks like strange.  The command string includes "LF" part at the last.  I believe it is supposed to be a correct Line Feed code (ASCII 0x0A), but you are incorretly sending "L" (ASCII 0x4C) and "F" (ASCII 0x46).  It must be a single byte of ASCII code 0x0A. Or the "LF" is correctly a part of command string?

[Mary NI]

Hi all,

I found a interesting Knowledgebase for Termination Characters in VISA.

http://zone.ni.com/devzone/cda/tut/p/id/4256

Regards,

Maria

NIE