Discussion:
Need an NI board to read 16 bit digital video (with frame and pixel input clock)
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Jaime F
2008-02-22 19:40:09 UTC
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Hi,

If you can explain a little bit more how your acquisition should happen? How are the image bits related to frames and pixels? How many pixels do you have per frame? &nbsp;I guess you are using 18 lines 16 for the image one for the frame sync and one for the pixel, right? Let's say you have a 10x10 pixel image, after you read 100 pixel you get a frame clock? Which card do you have: <a href="http://sine.ni.com/nips/cds/view/p/lang/en/nid/13510" target="_blank"> NI AT-DIO-32HS</a> ISA or PCI?

Either case this board can only be clocked from one source at a time. As we state at the help: The Sample clock is the primary time base for the DIO device. This clock controls the rate at which samples are acquired or generated. Each period of the Sample clock is capable of initiating the acquisition or generation of one sample per channel.

In your case I think you should be looking at the triggering capabilities of the card, as you can see on the manual:&nbsp; ?you can use a hardware trigger to start, stop, or pause/resume data transfer. Trigger signals should be connected as inputs to the PFI&nbsp;6 or PFI&nbsp;7 lines while configured for the sample clock sample timing type?.

I would strongly recommend taking a look at our <a href="http://www.ni.com/vision/" target="_blank"> Machine Vision</a> products they might have something more suitable for your application and you can always post in their discussion forum for support.

Waiting for your reply
Jaime F
2008-02-25 16:40:08 UTC
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Hi,

I?m glad I am able to help. To make sure that the PCI-1422 will do the job you can post your question a Vision and Motion discussion forum.

If you are still planning on using the DIO-32HS, what I?m thinking is using the pixel clock like you are right now as your sample clock to read from the digital lines and use the frame pulse &nbsp;to trigger the acquisition. Depending on how fast the frame pulse is sent you might be able to do a retriggerable acquisition every time the frame pulse is received. <a href="http://zone.ni.com/devzone/cda/tut/p/id/5382" target="_blank"> Retriggerable Analog Acquisition in NI-DAQmx</a> if you take a look at this article it should give you an insight on how can you do the same with ?digital input?. Take a close look at the: ?DAQmx Trigger? function in the LabVIEW help. &nbsp;Also remember the PFI line is going to be use as a trigger not as a clock.

Another approach you may&nbsp;take&nbsp;is to&nbsp;read all the pixels and the frame pulse and use post-processing on the signal to extract each frame, &nbsp;<a href="http://zone.ni.com/devzone/cda/epd/p/id/5005" target="_blank"> NI-DAQmx: Continuous Digital Pattern Acquisition</a> .

I hope it helps

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