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[Discuss-gnuradio] Help needed to understand scopesink2

From: Suleja, Lukasz
Subject: [Discuss-gnuradio] Help needed to understand scopesink2
Date: Fri, 3 Sep 2010 16:07:54 +0100

I am using the following code snippet to view a 100kHz sinewave on a virtual oscilloscope:

self.interface_rate = 1e9
self.src = "" gr.GR_SIN_WAVE, 1e3, 1)
self.scope = scopesink2.scope_sink_c(panel, sample_rate=self.interface_rate)
self.connect(self.src, self.scope)

As I increase the frequency of the sine wave to 100kHz, the resolution of the plotted points deteriorates.

With a sampling rate of 1MHz and a sine wave frequency of 100kHz, I would expect the time interval between plotted point to always be 1us. However, if I reduce the time-base and select the marker to be "Dot Larg" I can clearly see that the time-period is not the expected 1us.

Please could some one shed some light on why there appears to be a discrepancy; or are my expectation just incorrect.

I noticed that the scope base class makes references to message queues; is the discrepancy simply an OS timing issue.




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