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PCI DAQ card for QNX

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PCI DAQ card for QNX

Postby wantrg » Thu Jan 20, 2011 12:17 pm

Hi everyone,

I'm looking for a PCI DAQ card for real time control that has QNX driver.

Right now I've PDL-MF card from UEI with QNX driver, however this type of card can't be used since the data transfer is block transfer format which cause a huge delay in my application.

I hope somebody can help me to find a suitable PCI DAQ card for real time control. I would really appreciate it.

Thank you.

Wan
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Postby ingraham » Thu Jan 20, 2011 4:01 pm

You really haven't give us a lot of details, so it's hard to give you a particularly good answer. Main questions: What version of QNX? What kind of signals? What resolution do you need? How fast a sample rate? How long is a "huge delay?" Oh, and where are you? Your location (at least by continent) may have an impact and availability and local support.

Having said all that, I have at least to options for you to look into. The first is Advantech, which does document the register-level interface for their PCI DAQ cards. The seconds is National Instruments, which is of course THE name in DAQ. They have drivers for QNX 6.x. An earlier response to the question of PCI DAQ on QNX here on the forum also mention Measurement Computing, again having to use the register-level interfacer. http://www.openqnx.com/PNphpBB2-viewtopic-t6098-.html A quick Google search for "PCI DAQ QNX" also turned up this guy: http://www.superlogics.com/specpage.asp?Items=5217

I don't actually know off-hand whether any of them offer DMA as opposed to block transfers, but you can follow up with the vendors to find out.

Finally, dumb question; have you talked to UEI about the problem? They may be able to help.

Hope that helps.

-James Ingraham
Sage Automation, Inc.
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Postby wantrg » Fri Jan 21, 2011 12:20 pm

Hi James,

Thank you for your reply. Sorry for the lack of information. Currently I'm working on QNX version 6.4.0. The signals would be analog inputs from 6 channels of force transducer. The sensor requires 16-bit DAQ system and the sample rate is between 16.67kHz to 41.67kHz.

I've used the PDL-MF for data acquisition. Once acquisition is started, the DAQ board/driver transfer and store data into buffer at one rate and the application read the data from the buffer at another rate. This rate is depends on an event that send by the board driver to wake up the application thread that is responsible for processing data in the buffer. This cause a huge delay about 40-70ms. In other word, I just only can access the data every 40-70ms which cause a problem when I want to do real-time control application. The control loop bandwidth is 250Hz.

I already contact the NI, they don't have the QNX driver but offer the driver development kit (DDK). I need to write my own driver if I use NI card. I also talked to UEI about the problem. They said the card is designed for continuous gap free acquisition and it is not designed for acquisition/control type application like what I'm looking to do.

The second link that you posted before is the other card from UEI. I already ask UEI about other alternatives and still wait for the reply.


By the way I'm from UK.

Wan
wantrg
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Postby ingraham » Fri Jan 21, 2011 9:16 pm

Well, Advantech would be my top choice for the next thing to try. In the US a PCI-1716 is $450, a pretty reasonable price to give this thing a try. Yes, you will have to write some software, but it doesn't look too bad. I glanced through the manual, and annoyingly you can't just read all the channels directly, but you can cycle through them pretty fast. Of course, I don't know exactly how fast "pretty fast" will turn out to be. The thing to do is to get the card and give it a shot.

BTW, you didn't specify your output requirements, so I'm assuming it's some small number of analog channels, which the Advantech model I mentioned has two of. You might need additional hardware.

-James Ingraham
Sage Automation, Inc.
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