Digital Discovery Input Buffer Size

[stever]

HI,

I am using four outputs of the Digital Discovery to export a pattern and am trying to capture the pattern on another four DIO (not high speed input) pins.

It seems to work up to a length of 5024 but with longer pattern length I receive all zeroes.

The buffer size and trigger positions and number of samples are all linked to the pattern length.

The sampleformatset is set to 8 for 8-bits.

The pattern being generated is correct as verified on a scope.

Why can I not use pattern lengths up to the 32k mx buffer size ?

I was using a sample rate of 10MHz but if I increase it to 20MHz then I could get pattern length up to 8000.

Also I note that when I reduce the length back to a working length (after getting all zeroes) it doesn't seem to recover without actually power cycling.

Please advise

 

Thanks

stever

 

[attila]

Hi @stever

It should work up to 32k with PushPull output.

Here the Pattern generates a Custom binary counter:

[stever]

Hi Attila,

Thanks for quick reply

I am using python code in a script. I think the output pattern is created of correct length. It's just the data capture that fails.

Thanks

stever

[attila]

Hi @stever

Here you have an example from the SDK:DigitalIn_Acquisition_8x256M.py

[stever]

Hi Atilla, Yes, I followed DigitalAcquisition and DigitalIn_Record examples although I converted them to use the third party dwf API calls.

My script is working but only up to a reduced length of samples and that umber seems to depend on the sample rate.

I am trying to do simultaneous custom output pattern (on four pins) while capturing synchronously on two other pins.

Currently, I'm happy with the pattern output, but the testing I am doing with the output connected to other inputs (not high-speed ones) doesn't give me the expected values with longer pattern lengths (still less than 30K).

If I have a pattern length of 10000, are the following settings correct:

dwf.FDwfDigitalInBufferSizeSet(hdwf, c_int(10000))

dwf.FDwfDigitalInTriggerPositionSet(hdwf, c_int(9999))

dwf.FDwfDigitalInBufferSizeSet(hdwf, c_int(10000))

Thanks stever

[attila]

Hi @stever

This examples generates a counter and captures 100k samples at 100MHz:
DigitalIn_Acquisition_8x100k.py

[stever]

Hi Attila,

I solved the issue by adding the while loop to test the status of the acquisition.

Apparently just adding in a long sleep doesn't work.

I can now capture up to 32K samples.

If I try to go for more then I get dwf.lowlevel.DWFError: ERROR(19): Invalid bit count provided, so I'm not sure how the 100k example gets around it.

[attila]

Hi @stever

You are probably getting this error from FDwfDigitalOutDataSet, which expects the countOfBits max 32768 with DD.