Please first reference Troubleshooting General Boot Issues.
- After attaching power, the Red and Blue LEDs should light up. This indicates that the board is powered. Nothing will show up on HDMI or CVBS yet.
- At no point after attaching power should the Red LED blink or turn off. If this happens, it means that your power supply is inadequate. Please make sure that you are using a 5V power supply capable of supplying at least 1.5A (1500mA). Not having enough power could cause spontaneous reboots or software errors.
- The board will try to read the bootloader from the eMMC and then the MicroSD card from sector 1 (512B). If the correct signed bootloader is detected, the board will begin loading it and turn the Green LED on. If the Green LED does not turn on, it means that the software is not properly flashed onto the storage device.
- After about 3 seconds, the bootloader should turn on HDMI and displaying the loading sequence. Certain types of displays with odd resolutions are not supported at this stage and it might not display anything during this step and the next steps. If the Green LED turns green and nothing shows on your screen, please post your screen brand, model, and EDID below.
- The bootloader will attempt to EFI boot from a list of block devices:
- USB Flash Drive
It looks for an FAT/EFI partition with /boot/bootaa64.efi, loads the file into memory, and executes the it. On our images, bootaa64.efi is GRUB.