X series 6363/6368 Digital Output voltage level & LabVIEW port configuration

[Lefteris]

Hello all!

I would like to use the digital lines of the 6368 DAQ card and I need some clarification on the voltage level of the output.

On the specifications PDF it mentions the minimum and maximum, 0.8V & 2.2V respectively.

My question is, can the user control these levels OR this fluctuation is random?

It is important for me to know the exact output voltage.

A second question is related to LabVIEW.

If I configure the card to have lets say all ports outputs and then I need half of them to become inputs.

Do I need to stop the program and re-configure or can it happen on the fly?

Thank you in advance,

Lefteris

[crossrulz]

That spec is a little confusing.  The 0.8V and 2.2V are the input thresholds.  The DIO are typically designed to be able to accept LVTTL signals as inputs.  The outputs should all be at the 5V level.

[Lefteris]

Thank you for your fast reply!

I think I agree with you about the specs.

Just to clarify I am referring to the document 6368 specifications which can be found also here: http://sine.ni.com/ds/app/doc/p/id/ds-164/lang/en#currentlimits__fuse 

I am talking about the table titled "Electrical Characteristics" where they specify the MIN & MAX to 0.8 & 2.2 but then right after it the plots "Digital I/O Characteristics" include also values from 2.2V to 5.5V. On those plots it seems that the only factor that changes the output voltage is the temperature. Am i understanding it correctly or can the user choose the output voltage also?

[Stephan_D · Accepted solution]

Hi Lefteris,

according to the datasheet, it is NOT possible to control the exact level of the digital outputs. The output voltage depends on the supply voltage of the card, the ambient temperature and the current. The datasheet only guaranties that the output voltage for high level wouldn't be below 2,2V and the low level wouldn't be above 0,8V. If you want to control the voltage level more accurate, you could use the analog output, if you doesn't need to much current.

Cards like the NI PXIe-6535 offer the ability to set the output voltage of the DIO port to 2,5 or 3,3V, but the  6363/6368 doesn't offer this ability.

Your second question:

If you want to use all digital IOs as outputs and switch than to half input/output, you have to stop and destroy the task. It is not necessary to stop the whole program, but you have to destroy the the task. After that, you can start another task with the half input/output configuration.

Regards, Stephan