9188 PFI lines

[teoprimo]

Dear developers,

I'm using NI 9188 to realize a bridge based acquisition system and I'm going to use all of 8 slots with NI 9127 to comply it.

In this way I can't use NI9401 to take one simple TTL line as digital input. I don't need a hardware trigger to start acquisition but a signal that advise me of a change in my system status.

I'm thinking about using PFI lines to reach my purpose but I don't know how....

Can you help me?

[AntonisV]

Hello teoprimo,

please notice that the dio channels in 9401 are grouped in two ports, one containing channels 0, 1, 2, and 3, and one containing channels 4, 5, 6, and 7. The problem is that you have to configure the line direction before any of the tasks are started. In other words, you have to configure which lines you are going to use as inputs and which as outputs.

In the link below you can the way you can assign the NI 9401 for biderectional digital inputs and outputs using Daqmx.

https://decibel.ni.com/content/docs/DOC-11632

Also this link might be useful to you.

https://decibel.ni.com/content/docs/DOC-5765.

Remeber if you want to use counter/Timer I/O  on a cDAQ you need to use slots 5 and 6.

http://digital.ni.com/public.nsf/allkb/ADFC4DD8C9690232862575B70079FBD4?OpenDocument

I didnt understand very well the part " but a signal that advise me of a change in my system status". Do you mean you want to synchronize your signal with a counter for example?

 

[teoprimo]

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@Antonios V. wrote:

Hello teoprimo,

please notice that the dio channels in 9401 are grouped in two ports, one containing channels 0, 1, 2, and 3, and one containing channels 4, 5, 6, and 7. The problem is that you have to configure the line direction before any of the tasks are started. In other words, you have to configure which lines you are going to use as inputs and which as outputs.

In the link below you can the way you can assign the NI 9401 for biderectional digital inputs and outputs using Daqmx.

https://decibel.ni.com/content/docs/DOC-11632

Also this link might be useful to you.

https://decibel.ni.com/content/docs/DOC-5765.

Remeber if you want to use counter/Timer I/O  on a cDAQ you need to use slots 5 and 6.

http://digital.ni.com/public.nsf/allkb/ADFC4DD8C9690232862575B70079FBD4?OpenDocument

I can't use NI 9401 because I have filled all NI9188 slots with 8xNI9237.

I didnt understand very well the part " but a signal that advise me of a change in my system status". Do you mean you want to synchronize your signal with a counter for example?

 Ok. During signal acquisition, I will also have a TTL signal that I need to acquire. However, I have no space for NI 9401!

This is the reason because I'm thinking about using directly PFI lines.

 

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Thank you!

[AntonisV]

Hello teoprimo!

The only way you can use the PFI line is as a trigger to start an acquisition or generation.

You can not acquire and visualize a digital signal by using PFI line. You can not use PFI line as a digital input.

You have to use a digital input module in order to acquire a digital signal.

[teoprimo]

I have read it....but hope never dies 🙂

[John_P1]

Hi teoprimo,

Can you elaborate on what behavior you need out of the trigger line?  You can use it for counter tasks as well, so you actually have quite a bit of flexibility with what the line is capable of.

Best Regards,

[John_P1]

Just to further clarify, some of Antonios's responses were not entirely correct.  Please post back letting us know more details about what exact behavior you need out of the PFI line, I expect it will probably be achievable with some sort of counter task or even a static digital input--the PFI line supports both.

Best Regards,

[teoprimo]

Hi John,

I'm sorry for the delayed response.

I need a digital line to record an event that happens once during data acquisition.

This event is not a trigger, ence I can't use PFI lines as strart or reference trigger.

Thank you!

[John_P1]

Hi teoprimo,

What do you mean by "record an event".  The PFI line can be used for things other than triggers, contrary to Antonios's earlier post.

When this event occurs, what exact information do you need to record?

Best Regards,

[teoprimo]

I'm using 8 x NI 9237 to acquire signals that come from load cells.

During acquisition I receive a digital TTL signal, from another system, that I should record for diagnostic purpose.

I acquire analog signals contiuosly for one day and only one time, during acquisition, that digital line goes high.

Thank you very much!