FPGA Acquisition Process

NI InsightCM™ SDK 3.3 Help

Edition Date: December 2018

Part Number: 375191F-01

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This process acquires waveforms from channels on NI 9230 and NI 9232 C Series modules. This process transfers data from a device-specific FPGA bitfile that reads samples directly from the FPGA at the sampling rate configured for the device.

Actions Performed

  • This process reads waveforms from channels on dynamic modules. This process polls the DMA FIFO until enough samples are available to perform an actual read.
  • For tachometers connected to a module that supports high-speed acquisitions, this process locates the positions, in seconds, at which the tachometer generates pulses by using the number of generated pulses per revolution, the pulse width, and the arrival edge of the tachometer pulse. For example, an NI 9232 module in slot 1 of a cRIO-9036 chassis supports high-speed acquisitions of up to 100 kS/s.
  • For each channel, this process registers an alarm rule that causes the Trend Alarm process to monitor channel status tags for values other than ok.

Communicating with this Process

The SDK does not provide any messages you can send to this process specifically. This process continuously acquires data from all physical channels on dynamic modules.

Initialization Properties

You can set the following property in a software configuration definition. This process reads from the software configuration definition when it initializes.

SettlingTimeSeconds (Default: 30)—The number of seconds to wait after start-up before retaining data to pass to the first process in the Dataflow Script. This allows time for the AC coupling filter to settle.

Role within the Dataflow Script

This process sends messages to start the Dataflow Script after each read operation it performs. This process sends a separate message for each data group because each iteration of the Dataflow Script operates on a single data group.


  • This process bundles a data cluster for each data group that contains waveform channels to send with the Dataflow Script start message. The contents of this cluster are:
    • The data group name.
    • A copy of the point value map that contains some or all of the following elements:
      • Properties for the acquisition, such as the current data set number.
      • If the same data group contains single-point channels, this map contains the latest single-point values, which are written by the Scan Engine process.
        Note  For an illustration of this behavior, refer to Relationship between Data Acquisition Processes and Dataflow Script.
      • For tachometer channels, the map contains a PulsePositionsArray point whose value is an array of pulse positions from the tachometer.
    • An array of the waveforms acquired from channels in the data group, stored in a data value reference. For information about working with waveform data value references, refer to Reading and Writing Waveforms in a Data Set.
      Note  The Data Event Creator process writes the original waveforms acquired and buffered by this FPGA Acquisition process rather than waveforms bundled, acted on, and transferred between processes in Dataflow Script. This means any changes to the waveforms by Dataflow Script processes are discarded.

Related Information

Implementing Custom Data Acquisition

Scan Engine Process

Allowing Data to Flow between Processes in a Specific Order


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