6 Enabling PDM Microphones using the Device Tree Overlay

Pulse Digital Modulation (PDM) for microphones is a method used to convert an analog signal into a digital signal. The SAMA7G54-EK features four PDM microphones. For more information, refer to the Quad MEMS Microphones section in the SAMA7G54-EK User´s Guide (DS50003273), available on www.microchip.com.

Follow the steps below to use the device tree overlay to enable PDM microphones:

1. During booting, stop at U-Boot level by pressing Enter key to apply the device tree overlay to enable Quad PDM microphones.

   

2. Edit the bootcmd environment variable using the edit bootcmd command and apply the PDMC0 overlay by updating the string bootcmd from

   bootcmd=fatload mmc 1:1 0x63000000 sama7g5ek.itb; bootm 0x63000000#kernel_dtb

   to

   bootcmd=fatload mmc 1:1 0x63000000 sama7g5ek.itb; bootm 0x63000000#kernel_dtb#pdmc0.

   

3. To login as the root user, enter root.

   

This completes enabling PDM microphones with the pdmc0 device tree overlay.