Python API: decimation does not filter signal properly

Applications, development tools, FPGA, C, WEB
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aaronm
Posts: 2
Joined: Wed Jun 10, 2020 11:08 pm

Python API: decimation does not filter signal properly

Post by aaronm » Wed Jun 10, 2020 11:57 pm

Hi Red Pitaya users!

I'm using a STEMlab 125-14. I am having a problem with decimation when using the Python API on my device, comparing to the Oscilloscope feature. Specifically, the Oscilloscope seems to filter the signal, while this does not happen when I use the API. See attached plots. Here are some details:

Oscilloscope trace:
  • LV setting
  • 200 mV/div
  • 20 us/div
  • 15.625 MS/s (displayed sampling rate... 1/8th of 125 MS/s)
API trace:
  • osc0 as from the "Oscilloscope Forced Trigger" Jupyter example
  • osc0.decimation=8
  • osc0.filter_bypass has little effect (True or False).
Even choosing decimation=64 doesn't give as clean a trace as the Oscilloscope function. Has anyone else experienced something like this? The scope has the option to select LV (less noise) or HV (more noise), but I don't see this with the API.

Any ideas would be much appreciated! Thanks
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aaronm
Posts: 2
Joined: Wed Jun 10, 2020 11:08 pm

Re: Python API: decimation does not filter signal properly

Post by aaronm » Thu Jun 11, 2020 3:29 am

Also to point out:

setting "osc0.average = True" does not solve this.

33dnp
Posts: 2
Joined: Fri Jul 17, 2020 6:00 am

Re: Python API: decimation does not filter signal properly

Post by 33dnp » Fri Jul 17, 2020 9:57 am

Oscilloscope and Jupyter work on different versions of FPGA.
The results may vary.
To enable HV mode
osc0 = fpga.osc (0,20.0)

It would be nice to know the version of the ecosystem you are using.

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