Official sources:

Before touching any files, understand this order. If one step fails, the firmware won't "work."

Key fact: The A133 does not use UEFI or GRUB. You need livesuit/phoenixsuit or fastboot (if bootloader is intact).

If you’re building from source (e.g., a Linux BSP with Buildroot), follow these steps:

Allwinner provides a downstream U-Boot branch with specific A133 patches. You often need to enable or disable features:

Common task: Modify include/configs/sun50i_a133.h to change console baud rate or boot delay. Recompile with:

make CROSS_COMPILE=aarch64-linux-gnu- BL31=path/to/bl31.bin

Note: The A133 requires ARM Trusted Firmware (ATF) bl31.bin for booting Linux.

make -j$(nproc)

Output images appear in out/ – including full_img.fex which you flash to the device.