Waveforms 3.7.5 and oversampling

[Piotr Rzeszut]

Hi,

I have updated WF application and I see that oversampling is performing worse than in previous version.

3.7.5:

3.6.8:

Also for higher oversampling values there are visible some levels in the waveform:

3.6.8:

Is this physical effect (ex. sample & hold), or a bug?

Best wishes for everyone. PR

[attila]

Hi @Piotr Rzeszut

The oversampling requires external signal source since the ones produced by the device, Wavegen or Patterns, are synchronous with the Scope sampling.

WF version 3.6.x added 180*deg phase shift for Scope for Analog Discovery (1&2) which was suitable for oversampling 2x signals generated with AWG of the same device. This caused problems with some devices so it was removed for 3.7.x

Here you have the changelog and a blog about the new features:
https://reference.digilentinc.com/reference/software/waveforms/waveforms-3/change-logs/3-7-5
https://blog.digilentinc.com/software-update-waveforms-3-7-5/

[Piotr Rzeszut]

Also i have noticed, that when #2 configuration is selected (more samples for the scope), in Sample drop-down menu only 16k samples option is available.

[Piotr Rzeszut]

Hi @attila,

I have tested it with signal source not synced with AD2's clock, and it works perfectly!

Also (for attention of other people) similar thing we can observe using noise genrated by AD2 - the noise is randomized only when changing parameters of Wavegen channel used for generation this signal, and then it is repeated. When one want to use this noise to demonstrate how Scope's averaging works - it won't work well, even when generated with other AD device

Here I came up with an idea to allow noise to be generated (pseudo)randomly by the hardware (I know it would require to change FPGA configuration).

[attila]

Hi @Piotr Rzeszut

The noise in Wavegen and random in Patterns are generated in the device (FPGA), as you wanted
The confusion is caused by the Wavegen/Patterns preview which does not show the actual output for noise/random, just some PC random which updates when you change any setting.

[Piotr Rzeszut]

Hi @attila, 

I have been thinking of noise added to custom waveform (ex. sinus -> Alter with ... (add) -> noise), which someone may want to use to demonstrate averaging. 

 

[attila]

Hi @Piotr Rzeszut

At the moment you could use two AWG channels, one for signal and one for noise, and add them with wires/resistors.

Not the best option but you could also use frequency modulation to add noise.