This project is a PDM microphone simulator meant to be used as a hardware reference data source for DSP algorithms development and testing. The firmware runs on a 32 pin Nucleo-L432KC. Any other Nucleo board can be easily adapted as only a SPI slave interface is needed and STM32 Cube APIs are used.

Pinout

Signal	STM32 IO	Nucleo connector
PDM Clock	PA1	CN4-11 [A1]
PDM Data	PA6	CN4-7 [A5]
8MHz clkout	PA5	CN4-8 [A4]
2MHz clkout	PA9	CN3-1 [D1]
1MHz clkout	PA3	CN4-10 [A2]
LED DMAdone	PB3	CN4-15 [D13]

Apply PDM clock to PA1 and read resulting PDM data from PA6. A 1MHz clock is available on PA3 for testing purposes. The PDM data represents a 500Hz sinusoidal tone with a period of 2000 PDM samples. Such parameters have been chosen in order to represent an audible periodic PCM tone with the constraint for the PDM period to be a multiple of 8 which is the dimension of the minumum bit quantity that can be transferred via SPI interface.

The tone has been generated with Octave using the script in the 'Host' directory.