Samplesize seems to cause timeout.

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Samplesize seems to cause timeout.
« on: April 19, 2020, 09:35:26 AM »
I have a strange problem where when i set the sampleSizeL to specific values the scope stalls and subsequent calls to libusb_bulk_transfer timeout. The scope does not appear to stall immediately but some short delay after the new hardware settings are sent.

I set sampleSizeL to 10000 no problem. I start seeing captures
I set sampleSizeL to 6665 no problem. Again i see the samplesize change in the captures recieved after a short delay.
I set sampleSizeL to 10. Scope stalls after two or three captures of size 10 an no more data is returned

values of sampleSizeL I can switch between freely. 100, 1000, 10000, 6665, 2000, 3000 and probably many more.
values of sampleSizeL that cause the scope to fail. 10, 2999, 6666

When the sampleSize is changed to one of the suspect values, changing the size back to 10000 does not repair the scope. A reset and reupload of the fpga firmware is required to return it to working order.

Is this a bug? Is there a rule for what values are valid? In any case i think the scope should not freezup when a strange sampleSize is requested.
« Last Edit: April 19, 2020, 09:40:07 AM by maxwaldo »



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Re: Samplesize seems to cause timeout.
« Reply #1 on: April 20, 2020, 07:23:33 AM »
If I understand correctly, you are setting these values directly at the register level rather than via the software UI? If so then yes, there are rules that need to be considered when setting sample size:

sampleSize minimum is 256 (this due to the limit of USB transfer size - one USB packet is 1024  bytes)
 - sampleSize must be multiple of 4 (this is the limit of DDR3 RAM - single read/write)

 If you are setting frame size via the software these rules are already implemented
« Last Edit: April 20, 2020, 07:25:26 AM by Dejan »