read seems to return samples from the past

[mbaz]

The test setup is one laptop transmitting a sine wave using a B200 with gnuradio, and a second laptop receiving using an RTLSDR and SoapySDR.jl.

Samples are read from the RTLSDR using Base.read(stream, 10_000).

This is the sequence of events:

1. B200 transmitting; RTLSDR returns a clean sine wave.
2. B200 off; RTLSDR returns the same sine wave.
3. Julia restarted; RTLSDR returns noise (as expected).
4. B200 transmitting; RTLSDR returns noise (expected a sine wave).
5. Julia restarted; RTLSDR returns a sine wave (as expected).

One explanation is that read returns old samples stored somewhere. The ideal behavior is that samples are discarded by default; when reading, the specified number of samples are read from the device and returned; subsequent samples are discarded, until a new read is executed.

[sjkelly]

I wonder if this is related to #13. Can you see if the fix here helps: #13 (comment)

[mbaz]

@sjkelly Wrapping reads in between stream activation and de-activations helps.

[sjkelly]

Should be fixed in #22. Please comment or reopen if otherwise.