AnalogOutput

Prerequisites:

  • bonsai DAQmx Library
  • NI DAQmx driver from the NI website

Category: Sink

Brief: Writes a sequence of sample buffer to one or more DAQmx analog output channels

Input (OpenCV.Net.Mat) - C x N array where C is the number of connected analog output channels and N is the buffer size

Properties:

  • ActiveEdge(NationalInstruments.DAQmx.SampleClockActiveEdge) - the edges (Rising or Falling) of the NI-DAQmx device's sample clock signal used for signal generation
  • BufferSize (int) - the number of samples to generate for a single hardware buffer; it should be matched to the buffer size of the input nodes that define the analog output signal; the upper limit of the buffer (FIFO - 'first-in, first-out') depends on the DAQ board; it should be matched with
  • Channels (System.Collections.ObjectModel.Collection<Bonsai.DAQmx.AnalogOutputChannelConfiguration>) - all analog output channels that the voltage signal will be fed to, specified by adding channels in the AnalogOutputChannelConfiguration Collection Editor and setting its parameters as appropriate:
    • PhysicalChannel - the physical analog output channel on the board, selected from the drop-down list once the device is connected
    • ChannelName - can be anything
    • MaximumValue - maximum voltage value expected in the signal, not to be confused with device range
    • MinimumValue - minimum voltage value expected in the signal, analogous to MaximumValue
    • VoltageUnits - the units used to generate a voltage signal to the channel; for more information about the options (Volts or FromCustomScale), see the NI website
  • SampleMode (NationalInstruments.DAQmx.SampleQuantityMode) - specifies whether samples are generated until the task is stopped (SampleContinuous) or a specific number of samples, set by BufferSize, is reached (FiniteSamples)
  • SampleRate (double) - the number of samples generated per second. It should be greater than twice the highest frequency component in the emitted signal, respecting the Nyquist Sampling Theorem. The upper limit depends of the DAQ board.
  • SignalSource (string) - source terminal of the clock; if not specified, the internal clock of the device will be used

Output (OpenCV.Net.Mat):

  • IsInvalid (bool)
  • ElementType (int)
  • Size (OpenCV.Net.Size)
    • Width (int)
    • Height (int)
  • Rows (int)
  • Cols (int)
  • Step (int)
  • Depth (OpenCV.Net.Depth)
  • Channels (int)
  • ElementSize (int)
  • Data (System.IntPtr)
  • IsClosed (bool)
tip

Produce arbitrary input signals using FunctionGenerator

tip

Independent signals of OpenCV.Net.Mat type (1 x N arrays) can be merged using Zip --> Concat (#Dsp)

caution

Runtime Error: Device cannot be accessed

Most likely happens because the NI-DAQmx device is not connected/powered. Several other possible reasons and remedies are listed in the bonsai error message.

caution

Runtime Error: Requested value is not a supported value for this property. The property value may be invalid because it conflicts with another property.

With some NI-DAQmx boards (e.g. USB-6341), this is caused by the workflow containing multiple AnalogOutput nodes. Having to use a single AnalogOutput node means that the channel non-specific parameters (e.g. SampleMode) will be the same for all channels.

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