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TimJPL

Analog Discovery 2 Logic Analyzer Sample Rate

Question

I'm trying to watch an SPI interface running at 1MHz. When I try to set up the AD2 logic analyzer, I can't find the setting to change the sampling rate. It seems stuck at 200Khz. The AD2 advertises 2MS/sec, but I can't figure out how to configure the logic analyzer to do that.

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If by this you mean the "Base" dropdown list in the upper right hand corner, I lowered it to 500ns/div, but it still shows "2000 samples at 200Khz".

scope.png

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Press Single or Run to take new acquisition(s).

For 4 wire SPI add two SPI interpreters, one with MOSI and the other one with MISO data.

To acquire larger amount of samples than the 4k (or 2k sample + 2k noise) device buffer use the Record Mode. In this mode the sample rate is limited by the USB bandwidth to around 1-2MHz.

Edited by attila

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One more thought.  Is it possible to reduce the number of channels sampled in order to increase the sample rate in the record mode?  e.g. only sample 4 channels for a increase of 4x the sample rate?  

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@attilla - thanks for the confirmation. 

I have one more question - if the sample rate in record mode can be "1-2MHz", any suggestions for why I get error messages and warning messages right down to about 100kHz sample rate?  Is there anything I can do to ensure a consistent capture at 2MHz as that's what I need for my 400kHz I2C protocol?  I'm connected directly to my PC's USB port (no hub, although I tried that too).

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Such low record rate could be caused by some buggy USB 3 controllers or drivers. Some people say that an USB 2 hub solved this problem.
Unckeck recording noise to double the supported record rate.

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