How it works?
Unlike ODROID-N2, ODROID-C4 does not have SPI flash memory and there is no method to boot without an eMMC or SD card that has been flashed with a certain OS image includes the bootloader and OS platform. So the idea of supporting the Petitboot on ODROID-C4 is to copy the Petitboot image file
ODROIDBIOS.BINto the first partition along with the installed OS image and letting new version of U-boot loads the Petitboot image file on power cycle. The installation steps would be a bit confusing for some users who may be not familiar with the boot priority.
How can I install the Petitboot image?
The Petitboot image
ODROIDBIOS.BINmust be copied to:
 eMMC when it's attached along with SD card or not.
 SD card only when it's attached without eMMC.
Can I boot from USB storage without an eMMC or SD card?
No, since ODROID-C4 is not possible to boot without a bootloader from an eMMC or SD card since it does not have on-board booting device. In order to boot from USB storage through the Petitboot, you will need a small SD card that is bootable from ODROID-C4.
- The first version 20200717 would be unstable.
- Certain OS version in the SD card won't appear in the menu list after rebooting, please let me know if you have the same issue.
- After OS update and it overwrite U-boot, multiboot support would not supported since the change for multiboot I made is not merged to official U-boot yet. In case this happens, U-boot must be flashed back if my change is not merged to official U-boot.