- After reset, the program counter starts at the beginning P6 internal ROM. In this internal ROM, some kind of pre-bootloader exists that evaluates external pins and selects the corresponding boot mode (e.g. boot over USB, NAND, IIC, UART, ... ). Depending on the selected mode, the peripherals are set-up and it is tried to boot over this peripheral.
- Boot over NAND: The pre-bootloader starts the memory controller, copies the bootloader from NAND to internal RAM and sets the program counter to the address in internal RAM which basically starts the bootloader.
- Boot over USB: The pre-bootloader listens to USB and waits for the "Hello P6" command. If received, it replies and awaits an image (the usb_bootloader.bin). The received data is copied to internal RAM and the program counter is changed to the internal RAM address wich in effect starts the bootloader.
- Depending on the started bootloader, either the UBI partitions are "mounted" and the kernel image is read or the bootloader waits until the kernel image is sent over USB.
- If the installer.plf (which is basically a kernel image) is booted over USB, the "init" command of this image awaits the actual firmware (ardrone_update.plf) over USB and installs the content to NAND.
Sunday, January 9, 2011
A.R. Drone's boot sequence
In order to be able to flash a custom kernel to A.R. Drone, it is necessary to understand it's boot sequence:
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Hi.
ReplyDeleteI have a malfunctioning drone and I am testing your tools. They are great, but I want to add one step to your Boot over USB sequence:
After the "Hello P6" command, the drone changes something on the USB interface, and a 'new' device is detected: "Gadget Serial V2.4" and will ask for drivers again. This means that on a new computer the 1st update attempt will fail because the usb_flash utility will time out before you can install the drivers.
Also, I made my cable with a low quality USB cable, and after "Hello P6" the system complains about a non-recognized USB device (VID_0000 PID_0000). Then I got a good quality USB 2.0 cable and I was able to correctly install the 2nd device, so I suspect the 2nd device negotiates for USB 2.0. If someone have this same problem it may be worth to try and make a better cable!
Once again...great tools, keep the good work!
Still I couldn't solve my drone problem :(
Hi,
ReplyDeleteThanks for your useful post.
My drone has been damaged and does not enter to busybox and shows 'kernel panic' error message.
Now I want to boot it from USB, but when I connect a USB power the drone on, it doesn't recognize the USB.
How can I force the drone to boot from USB? What files should be copied to USB for booting?
Thanks a lot
Hi,
ReplyDeleteI know this is an old post but I'm grasping at straws now! I too am getting a kernel panic after I added libc.so.6 to /lib. Have you any ideas how I could fix this?
Many thanks,
Andy