1 Sample versus N Samples Modes (ELVIS RIO Control Toolkit)

LabVIEW 2016 ELVIS RIO Control Toolkit Help

Edition Date: June 2016

Part Number: 376300A-01

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The NI ELVIS RIO Control Toolkit provides VIs for you to perform two I/O modes of signal acquisition and generation: 1 sample and n samples. Use the following table to learn about these modes.

Note  You can perform n samples operations only after you install the NI High Throughput Add-On for ELVIS RIO Control Module. Visit ni.com/info and enter the Info Code exqmja to learn about the NI High Throughput Add-On for ELVIS RIO Control Module.
Operation I/O Mode Description Use Case
Signal Acquisition 1 Sample The NI ELVIS RIO CM acquires one sample each time for a single channel or multiple channels. This mode uses software-timed acquisition. The sample rate of acquisition depends on the software loop rate on the real-time processor. Various factors can affect this loop rate, such as simultaneous running of multiple programs on the NI ELVIS RIO CM target. Acquiring the most recent value or periodically monitoring low frequency signals, such as the temperature.
N Samples The NI ELVIS RIO CM acquires multiple samples at the same time for a single channel or multiple channels. This mode has the following characteristics:
  • Hardware-timed acquisition—The FPGA target on the NI ELVIS RIO CM has a 40 MHz clock rate, which controls the rate of acquisition. The sample rate depends on the hardware clock, which is faster than a software loop. A hardware clock is more accurate than a software loop. Therefore, you can have accurate control over the time between each sample.
  • Buffered acquisition—FPGA transfers the samples from the FPGA target to an intermediate memory buffer using direct memory access (DMA) before LabVIEW reads these samples on the real-time processor.
Acquiring finite high frequency signals.
Signal Generation 1 Sample The NI ELVIS RIO CM generates one sample each time for a single channel or multiple channels. This mode uses software-timed generation. The sample rate of generation depends on the software loop rate on RT side. Various factors can affect this loop rate, such as the simultaneous running of multiple programs on the NI ELVIS RIO CM target. Generating the most recent value or generating low frequency signals. For example, generating a known voltage to stimulate a device.
N Samples The NI ELVIS RIO CM generates multiple samples at the same time for a single channel or multiple channels. This mode has the following characteristics:
  • Hardware-timed generation—The FPGA target on the NI ELVIS RIO CM has a 40 MHz clock rate, which controls the rate of generation. The sample rate depends on the hardware clock, which is faster than a software loop. A hardware clock is more accurate than a software loop. Therefore, you can have accurate control over the time between each sample.
  • Buffered generation—The real-time processor takes the samples from LabVIEW and places them in an intermediate memory buffer using DMA before FPGA gets the samples from the buffer.
Generating finite time-varying signals, such as an AC sine wave.

After you install the NI High Throughput Add-On for ELVIS RIO Control Module, you can refer to High Frequency Sampling.lvproj in the labview\examples\EL-RIO-CM\High Frequency Sampling directory for an example of comparing the 1 sample mode with the n samples mode using the NI ELVIS RIO CM Express VIs.

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