I've recently packaged the sunxi tools for Debian. These are a set of tools produce by the Linux Sunxi project for working with the Allwinner "sunxi" family of processors. See the package page for details. Thanks to Steve McIntyre for sponsoring the initial upload.

The most interesting component of the package are the tools for working with the Allwinner processors' FEL mode. This is a low-level processor mode which implements a simple USB protocol allowing for initial programming of the device and recovery which can be entered on boot (usually be pressing a special 'FEL button' somewhere on the device). It is thanks to FEL mode that most sunxi based devices are pretty much unbrickable.

The most common use of FEL is to boot over USB. In the Debian package the fel and usb-boot tools are named sunxi-fel and sunxi-usb-boot respectively but otherwise can be used in the normal way described on the sunxi wiki pages.

One enhancement I made to the Debian version of usb-boot is to integrate with the u-boot packages to allow you to easily FEL boot any sunxi platform supported by the Debian packaged version of u-boot (currently only Cubietruck, more to come I hope). To make this work we take advantage of Multiarch to install the armhf version of u-boot (unless your host is already armhf of course, in which case just install the u-boot package):

# dpkg --add-architecture armhf
# apt-get update
# apt-get install u-boot:armhf
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following NEW packages will be installed:
0 upgraded, 1 newly installed, 0 to remove and 1960 not upgraded.
Need to get 0 B/546 kB of archives.
After this operation, 8,676 kB of additional disk space will be used.
Retrieving bug reports... Done
Parsing Found/Fixed information... Done
Selecting previously unselected package u-boot:armhf.
(Reading database ... 309234 files and directories currently installed.)
Preparing to unpack .../u-boot_2014.04+dfsg1-1_armhf.deb ...
Unpacking u-boot:armhf (2014.04+dfsg1-1) ...
Setting up u-boot:armhf (2014.04+dfsg1-1) ...

With that done FEL booting a cubietruck is as simple as starting the board in FEL mode (by holding down the FEL button when powering on) and then:

# sunxi-usb-boot Cubietruck -
fel write 0x2000 /usr/lib/u-boot/Cubietruck_FEL/u-boot-spl.bin
fel exe 0x2000
fel write 0x4a000000 /usr/lib/u-boot/Cubietruck_FEL/u-boot.bin
fel write 0x41000000 /usr/share/sunxi-tools//ramboot.scr
fel exe 0x4a000000

Which should result in something like this on the Cubietruck's serial console:

U-Boot SPL 2014.04 (Jun 16 2014 - 05:31:24)
DRAM: 2048 MiB

U-Boot 2014.04 (Jun 16 2014 - 05:30:47) Allwinner Technology

CPU:   Allwinner A20 (SUN7I)
DRAM:  2 GiB
In:    serial
Out:   serial
Err:   serial
Target spinup took 0 ms.
AHCI 0001.0100 32 slots 1 ports 3 Gbps 0x1 impl SATA mode
flags: ncq stag pm led clo only pmp pio slum part ccc apst 
Net:   dwmac.1c50000
Hit any key to stop autoboot:  0 

As more platforms become supported by the u-boot packages you should be able to find them in /usr/lib/u-boot/*_FEL.

There is one minor inconvenience which is the need to run sunxi-usb-boot as root in order to access the FEL USB device. This is easily resolved by creating /etc/udev/rules.d/sunxi-fel.rules containing either:

SUBSYSTEMS=="usb", ATTR{idVendor}=="1f3a", ATTR{idProduct}=="efe8", OWNER="myuser"


SUBSYSTEMS=="usb", ATTR{idVendor}=="1f3a", ATTR{idProduct}=="efe8", GROUP="mygroup"

To enable access for myuser or mygroup respectively. Once you have created the rules file then to enable:

# udevadm control --reload-rules

As well as the FEL mode tools the packages also contain a FEX (de)compiler. FEX is Allwinner's own hardware description language and is used with their Android SDK kernels and the fork of that kernel maintained by the linux-sunxi project. Debian's kernels follow mainline and therefore use Device Tree.