I am debugging an SPI problem involving the Analog Devices AD7276, the firmware of which runs on an ATSAMG55J19.
We are capturing 14 consecutive DMA reads of a shaped sinusoidal-like waveform (within about 5uS). The SPI read is kicked off through a fast comparator which is set to about 0.45V, with the waveform maximum amplitude of approx 3.0V.

The original issue being investigated are reads within the 14 that are either zero or much lower in value than adjacent reads. Given the waveshape, these anomalies do not make sense.
Bringing tools from ScanaQuad and selae into the battle, we must operate our SPI at 10MHz or less in order to capture the SPI data. However, our SPI must run at least at 20Mhz, preferably 30, in order to capture a sufficient portion of the signal.
I've searched, and cannot find protocol analyzers (reasonably inexpensive) that can do this job.
Any recommendations out there?

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