niUSRP Fetch Rx Data (CDB)

Fetches complex, double-precision floating-point data from the specified channel.

Inputs/Outputs

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session handle

Instrument session.

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error in

Error conditions that occur before this node runs.

The node responds to this input according to standard error behavior.

Standard Error Behavior

Default value: No error

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number of samples

Number of samples to fetch from the acquisition channel.

For finite acquisitions, if you specify a value of -1, NI-USRP returns all the remaining samples. NI-USRP returns the samples when the requested number of samples is retrieved from the device or when the timeout is exceeded, whichever happens first.
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timeout

Time to wait, in seconds, before returning an error if the requested number of samples have not been acquired.

Default value: 10

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channel list

Channel(s) from which to fetch the data.

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session handle out

Reference to your instrument session to be passed to the next node.

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error out

Error information.

The node produces this output according to standard error behavior.

Standard Error Behavior

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data

Received baseband samples as an array of complex, double-precision floating-point data.

The real and imaginary parts of this complex data array correspond to the in-phase (I) and quadrature-phase (Q) data, respectively. Because the USRP is not a calibrated device, the units returned by data do not correspond to volts or dB. The Power Spectrum node used in many of the example nodes returns the magnitude spectrum in Vrms^2 or dB relative to 1 Vrms/1 _. If you set the Power Spectrum input to return the spectrum in Vrms^2, you can convert Vrms^2 to volts.

The time between samples in the waveform (the sample period) equals 1 divided by the coerced I/Q rate. Determine the coerced I/Q rate by reading the IQ Rate property after you set it or by reading the coerced IQ rate output of Configure Signal.

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timestamp

Timestamp of the first receive (Rx) sample returned and the time associated with the first sample of the waveform, according to the onboard device timer.

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whole seconds

Integer number of seconds for the time associated with the first sample of the waveform, according to the onboard device timer.

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fractional seconds

Double-precision, floating-point value representing the remaining fraction of a second for the time associated with the first sample of the waveform, according to the onboard device timer.

Hardware Support

This node supports the following hardware:

  • USRP-2900/2901
  • USRP-2920/2921/2922
  • USRP-2930/2932
  • USRP-2940/2942/2943/2944/2945
  • USRP-2950/2952/2953/2954/2955