DAQmx and SPI Timing

[JayKaye]

I am attempting to use a PXIe-6537 Digital I/O Module to communicate with a DUT using the SPI protocol. I have evaluated the sample programs from the SDW toolkit, specifically "DAQmx SPI - Internal Clock.vi" and it originally looked like the 6537 can support what I need to do. However, my requirement is to use SPI to transmit data items at a fixed 20 kHz rate, and the example code seems to transmit the data at the fastest rate possible, using the "Oversample clock rate" control value of 10M to set the DAQmx Timing parameters. I do want to use the typical 1 MHz for the SPI clock (SCLK) frequency, it's just that my data stream needs to go across the channel at a fixed rate of 20 kHz.

I have looked at many forum entries and have tried a bunch of alternate vi schemes, but I can't seem to find a way to successfully regulate the digital output rate of the SPI packets. Can anyone help?

[sherlockholm]

Hi JayKaye,

I noticed this forum thread is a little old. I would recommend creating a new thread, so it can get more views. You can link to this thread, but creating a new one will help others see it, and then they can give their suggestions.

Something I did find that I wonder if it would be helpful to you is this white paper:

Serial Protocol Communication Reference Design for Digital Waveform Devices

http://www.ni.com/example/31200/en/

Hope this helps!