I'm having a similar problem, all with USB audio.
But while this tutorial is superb, I'm encountering the same issue: I can't get RATT to log what I'm looking for.
The cumulative histogram information is blank:
"Cumulative Histogram for: ()"
And while I have *huge* ISR count numbers, everything is zeroed out for DPC/DPCTmr.
So far at 6 runs.
Also interesting: DPC Latency Checker is actually showing everything "in the green." I'm suspicious that the poll frequency is exactly out of phase with the actual problem. sysinternals Process Explorer shows clear DPC spikes around 50%(!) every half minute.
I feel like perhaps I don't fully understand how to operate RATT? Or maybe I just have a use case that RATT can't accurately diagnose?
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