I am trying to drive a 521 using SPI hardware to drive the PDM clock (1Mhz) and capture pulses.
(Yes this is a hack but its been done before, see http://www.cypress.com/?app=forum&id=2232&rID=43249)
I can see variable PDM data come in when I clock the IC (and after its woken up).
When I drove a 521 and then LPF'ed the data pulses using a 10Khz filter, I could see the waveform with a 'scope, but only 180mV peak to peak.
Is this normal operation? Why, with a very loud tone, don't I see more amplitude? Shouldn't we get lots of FFF.FF and 000...00 sequences that represent full-scale measurements?