5 Apply the Device Tree Overlay to Enable PDM Microphones
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 the PDM microphones:
- During booting, press ENTER to
stop at U-Boot level and apply the device tree overlay to enable the Quad PDM
microphones.
-
- 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_dtbto
bootcmd=fatload mmc 1:1 0x63000000 sama7g5ek.itb; bootm 0x63000000#kernel_dtb#pdmc0 - Use the saveenv
command to save the bootcmd variables previously set in the environment
permanent storage space.
- Edit the bootcmd environment variable using the edit bootcmd
command and apply the PDMC0 overlay by updating the string bootcmd
from
- Enter the boot command to boot
the kernel and dtb.
- To log in as the root user, enter root.
This completes enabling PDM microphones with the pdmc0 device tree overlay.