Hi,
The default images that you build works for the eMMC but to boot the image from the SD card, you need to follow the below instructions:
3.4.3 Building Android image for the SD card on the SABRE-SD
Board
The default configuration in the source code package takes internal eMMC as the boot storage. It can be changed to make the
SD card in SD Slot 3 as the boot storage as follows:
remove out/target/product/sabresd_6dq/root directory and boot*.img
remove /out/target/product/sabresd_6dq/recovery directory and recovery*.img
remove /out/target/product/sabresd_6dq/system directory and system*.img
$ make BUILD_TARGET_DEVICE=sd
Follow Section 3.4 to build the images.
For more information please refer to the Android_User_Guide.pdf from the documentation section.
Thanks and Regards,
-Devaraj