Re Triggering Using PCI 6534 and PCI 6602

[057768022]

Hi Travis,

We set the PCI 6602 and PCI 6534 according to your instructions. (MAX was set to RTSI cable and PCI 6602 and PCI 6534).

We saw that the CLK is generated upon each external trigger. W enoticed that the data was generated at the CLK timing. (That is fine)

We also saw that the data isn't in sync with the trigger. (It seems that the data is looping in the memory)

Our motivation is to generate a new pattern on each trigger.

I added a figure with our problem.

How can we restart the memory upon each trigger?

Best Regards,

Nir

[Travis G.]

Hello Nir,

There are a few things you can do to modify this behavior.  The first is to configure the NI-6534 device to not allow regeneration.  This will cause any data points written to the device to only be generated once, and disable the generation from continuously going back to the beginning of the buffer and looping through the samples.  You can configure your NI-6534 device to not allow regenerating using the Regeneration Mode property, found within the DAQmx Write Property Node. 



One thing to realize is that by configuring the device to not allow regeneration, if you do not provide enough data for the number of sample clock ticks the device receives, the DAQmx driver will throw a buffer underwrite error (error code -200166).  If you get this error, you can either ignore it by programmatically checking the status code and clearing the error, or you can ensure that data is always available to write by making sure that the exact number of necessary sample clock ticks are sent by the NI-6602 device each trigger period.  Basically, you would want to configure the finite pulse generation task on your NI-6602 to output a number of pulses equal to the number of samples you've written to the buffer, and continually match these up each trigger period.

I hope this information helps, and if you would rather speak to a National Instruments Applications Engineer by phone, you can create a service request online at www.ni.com/contact.

Regards,
Travis G.
Applications Engineering
National Instruments
www.ni.com/support

Message Edited by Travis G. on 11-02-2006 12:26 PM

[057768022]

Hi Travis,

We tried this approach - it didn't help.

I added our *.vi figure.

What else can be done, in order to generete dis continous triggered data?

[Travis G.]

Hello Nir,

You will want to place the DAQmx Write Property Node to not allow regeneration once in your program prior to any data being written to the device.  When you say this doesn't work for you, does your program throw an error, or is the data being regenerated?  How much data are you writing to your buffer each iteration of the loop?  How many sample clock ticks are you sending to the NI-6534 from the NI-6602 upon each trigger signal?  The number of sample clock ticks and the number of samples written to the buffer should be the same.  To make troubleshooting easier, it may be better to work from a proof of concept example program to make sure that there aren't problems with the programming. I've written a basic example program that should do what you need and attached it to this post.  I have only tested this example with simulated DAQ devices, but I would like you to give it a try with your hardware, monitor the output with your scope, and describe the behavior you are seeing.  Also, compare the example program to yours and try to identify any differences.  Let me know how this goes.

Travis G.
Applications Engineering
National Instruments
www.ni.com/support