Single PDM microphone at higher PCM sampling rate

Hello,

we need to feed mono audio data into the nRF52 and we are now evaluating the possibility to use PDM. The nRF52 seems to have a useful PDM interface, and even though an example does not seem to exist in the SDK [what a pity!], there is a PDM driver. There also seem to be many PDM microphones available, like from Knowles or InvenSense.

All of these mics are sensitive to 20+ KHz, which we would like to make use of. We planned to have 48 KHz sampling rate and I wondered how and where I could set that in the PDM driver.

After some search, on the PDM Interface site of the Nordic Infocenter I found that the PDM features "16 kHz output sample rate, 16-bit samples". So does it mean that the sample rate cannot be changed? Is this a driver issue or is this a limitation of the PDM hardware used? If the latter is able to handle stereo signal at 16 KHz, I would at least expect it to handle mono signal at 32 KHz without overhead.

Can you please comment on that or propose a hack to change the PCM sampling rate? Thank you!

NewtoM