🛠 Boot SD/eMMC et récupération (pyamlboot) sur Amlogic S905X

Objectives

Understand the Amlogic boot chain (proprietary BL2/BL30/BL31 blobs + mainline U-Boot signed in FIP), install Armbian on microSD, flash the eMMC from a running system, and recover a non-booting board via USB bootrom and pyamlboot. Boot failures ("boot loop", "red + blue LED only") are the board's #1 support topic: bad SD card, weak power supply, or inconsistent image/bootloader mix.

Hardware

• Le Potato AML-S905X-CC (v1: micro-USB 5 V/2.5 A; weak power supply = silent hangs)
• Quality microSD card, Armbian "lepotato" image (dl.armbian.com/lepotato/)
• Optional eMMC module (no standalone eMMC boot path: flashing is mandatory from a running system, using the LEFT tool)
• USB cable for recovery, Linux PC

Full Code

# 1) Ecrire l'image Armbian sur la SD (bootloader U-Boot deja integre)
xzcat Armbian_*_Lepotato_*.img.xz | sudo dd of=/dev/sdX bs=4M status=progress conv=fsync
# Bootloader U-Boot construit a la main (doc officielle) : deux passes dd, offset 8 Ko
# dd if=u-boot.bin.sd.bin of=/dev/sdX conv=fsync,notrunc bs=512 skip=1 seek=1
# dd if=u-boot.bin.sd.bin of=/dev/sdX conv=fsync,notrunc bs=1 count=440

# 2) Depuis le systeme demarre : flasher l'eMMC puis installer
sudo apt install git && git clone https://github.com/libre-computer-project/libretech-emmc-flash-tool
cd libretech-emmc-flash-tool && sudo ./emmc-flash-tool   # outil LEFT
sudo armbian-install

# 3) Recuperation : maintenir le bouton de boot puis brancher l'USB,
#    le bootrom Amlogic apparait sur le bus USB :
sudo pip install pyamlboot
lsusb            # appareil Amlogic visible = bootrom accessible
sudo ./boot-aarch64.sh   # script pyamlboot : demarrer un noyau en RAM

Expected Verification

cat /proc/device-tree/compatible contains libretech,aml-s905x-cc amlogic,s905x amlogic,meson-gxl; in recovery mode, lsusb shows the Amlogic bootrom device before any action, and pyamlboot can load a kernel into memory.

Common Errors

• Mixing legacy "box" images (Android 3.14/4.9) with mainline: incompatible, no in-place updates; installtointernal scripts break mainline boot.
• Cheap SD card or marginal 5 V power supply: boot loop without error messages.
• Attempting to boot directly from eMMC: without prior flashing via LEFT, the eMMC has no standalone boot path.
• Overheating: the S905X gets hot without a heatsink — add a heatsink.