The PDM has a very simple digital interface but it's not PWM or I2S, so the chip has to have a PDM interface. Most 32-bit processors available do. PDM is a little like 1-bit PWM. Clock the mic with a 1-3MHz clock rate, and on the data line to get a square wave out that syncs with the clock. The data line with be 0 or 1 logic output, with the square wave creating a density that, when averaged, will result in the analog value out.