DAQ6353 // Set Digital Input to float/tristate

[ThomasPujolle]

Hi all,

I have a sensor signal connected to one digital input (P0.5) of my DAQ6353, since that sensor signal can be configured to output a digital or analog signal I have also connected it to an analog input to be able to read something in both scenarios.

In a nutshell:

Sensor Out --> | P0.5 on DAQ6353  (Digital Input, default level HIGH)

                          | AI0 on DAQ6353  (Analog Input)

The issue:

My DAQ6353 configures the P0.5 to be 5V by default, possibly using an internal pull up. Since both the analog and digital input are tied together the digital input is constantly driving high the analog input, preventing me from reading anything.

Target solution:

Set the Digital Input to tristate/float in order to let me read the analog ouput of my sensor.

Problem:

I created a VI to set P0.5 to tristate, without success, here is my diagram and attached is the .VI:

I'm probably close to the solution, a little help would be much appreciated.

Thanks in advance !

[GerdW]

Hi Thomas,

the manual of the NI6353 doesn't mention TriState behaviour at all.

Why do you think your DAQ hardware supports this feature?

[ThomasPujolle]

I must mention its a PCIe-6353, I assumed the tristate was possible because I can configure it in NI-MAX as startup state:

[GerdW]

Hi Thomas,

the manual for the PCIe6353 is the same as I linked before.

It still not mentions any TriState behaviour…

[JÞB]

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@ThomasPujolle wrote:

Hi all,

I have a sensor signal connected to one digital input (P0.5) of my DAQ6353, since that sensor signal can be configured to output a digital or analog signal I have also connected it to an analog input to be able to read something in both scenarios.

In a nutshell:

Sensor Out --> | P0.5 on DAQ6353  (Digital Input, default level HIGH)

                          | AI0 on DAQ6353  (Analog Input)

The issue:

My DAQ6353 configures the P0.5 to be 5V by default, possibly using an internal pull up. Since both the analog and digital input are tied together the digital input is constantly driving high the analog input, preventing me from reading anything.

Target solution:

Set the Digital Input to tristate/float in order to let me read the analog ouput of my sensor.

Problem:

I created a VI to set P0.5 to tristate, without success, here is my diagram and attached is the .VI:

I'm probably close to the solution, a little help would be much appreciated.

Thanks in advance !

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You are not quite as close as you think you are🙃

Actually you have the right idea  tri-Stating the DI line is a well thought out approach.   Unfortunately, you have the wrong hardware Read this  and look closely at page 6-2.  The 6353 Digital lines have an internal weak pull-down (50k typical, 20k min per the specification sheet.)  I can only imagine that someone suppressed an error in there somewhere (Arguably, Tristate=FALSE is valid so. maybe a TRUE value is not truly an error)

Looking at your Channel property node.  You need to reorder the inputs so you select the active channels before setting the tristate property.   The way you have it is analogous to "Ready, Fire, Aim." 

[ThomasPujolle]

Ok so even if I get the .VI right my hardware won't allow that. Would a PFI line do the job then ? Ff I can toggle it between analog input and digital input?

[GerdW]

Hi Thomas,

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@ThomasPujolle wrote:

Would a PFI line do the job then ? Ff I can toggle it between analog input and digital input?

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AFAIK you cannot switch a PFI between "digital" and "analog" operation mode!

You could use one more DO channel to switch on/off an external relais. This way you can easily set your DO output to "fake TriState"…