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Just want to note that I (gena2x) decided to provide and support U-Boot as far as I can. To find info on my latest U-Boot version with bug-fixes, description how to setup u-boot, list of known bugs please visit U-boot-gena2x

Outdated warning ! This article or section is significantly outdated, either by significant hardware or software changes. Procedures mentioned in this page may well not work for current hardware/software.

U-Boot menu on Neo 1973

U-Boot is a bootloader which can be used on the Neo 1973 and Neo FreeRunner. It takes care of device functionality until the operating system is booted. This includes USB DFU for Flashing the Neo FreeRunner, a splash screen, a boot menu, a console for U-Boot commands, configuration via U-Boot environment, and loading a kernel.


Booting into U-Boot

  • Make sure that your phone has had the battery and USB cable removed for at least 30 seconds.
  • Hold in the AUX button on power-up to access the boot menu.
  • Connect the Neo (ie not Debug Board) to a Linux host with the USB cable.
  • Set the console to USB.
  • Connect to /dev/ttyACM0 with a terminal program on the Linux host (you might need to chown uucp.uucp /dev/ttyACM0; see also below)
  • Note that the cdc_acm /dev/ttyACM0 access disappears as soon as the Neo boots, and is replaced by the cdc_ether usb0 network access.
  • You're now at the U-Boot prompt.
  • Set the bootdelay U-Boot environment variable to -1 if you want it to always halt at the U-Boot on power-up.


More information on U-Boot can be found at

Additions to the vanilla U-Boot already implemented include:

  • Support for boot from NAND flash using S3C2410 Steppingstone
  • Support for S3C2410 NAND flash
  • Support for downloading programs via S3C2410 USB Device Controller
  • Support to display bootup logo / status on S3C2410 Framebuffer

However, U-Boot still doesn't support many of the features that GTA01 needs, such as

  • Support for reading kernel/initrd from SD/Transflash

HaraldWelte is working on those issues, and in fact most of them have already been implemented.

U-Boot source code

The current U-Boot source can be found at http://git.openmoko.org/?p=u-boot.git;a=shortlog;h=stable .

To get U-Boot by git:

 git clone git://git.openmoko.org/git/u-boot.git openmoko/u-boot

To build U-Boot:

  • Clone the git tree and check out the stable branch (commands from above)
  git checkout origin/stable
  • Set the CROSS_COMPILE environment variable to specify the prefix to your toolchain binaries
  • Run "make gta02v5_config" (or gta01bv4_config, or whatever hardware revision you have)
  • Run "make u-boot.udfu". This will give you an image which you can install with dfu-util, or which you can upload into memory via JTAG (with a debug board)

All together:

 git clone git://git.openmoko.org/git/u-boot.git openmoko/u-boot
 cd openmoko/u-boot
 git checkout origin/stable
 export CROSS_COMPILE=arm-angstrom-linux-gnueabi-
 make gta02v5_config
 make u-boot.udfu

U-Boot binary

The latest U-Boot binary builds can be found under:

All versions of the GTA02 (Neo FreeRunner) that have been sold to the public are version 5 hardware, so look for a file with "gta02" and "v5" in the name, for example:


The file should be written to the NAND flash address 0x00000000 (size 0x30000) (the first partition).

U-Boot development


If you want to do U-Boot development on the QT2410, it's easier to work with a U-Boot image that can be downloaded via USB into RAM instead of flashing.

To do so, you need to edit the u-boot/include/configs/qt2410.h file, and change the "if 0" in Line 32 into a "if 1", then recompile with "make".

The resulting "u-boot.bin" is _NOT SUITABLE_ for NAND flash, but only for direct execution from within ram, e.g. by using the s3c2410_boot_usb program.

Neo 1973

Doing U-Boot development on the Neo 1973 is a bit more tricky. First, we don't have any NOR flash. Second, there is no other way to boot _but_ from NAND. Therefore, we also don't have a USB downloader like the QT2410.

The main problem is: The S3C2410 Steppingstone unconditionally copies the first 4k of flash into its internal SRAM. That SRAM segment stays unconditionally mapped at physical address zero. How do we get around this

Neo FreeRunner

Main article: Neo_FreeRunner_Memory_Mapping

Using JTAG to boot from RAM

So how can we boot from RAM? We use JTAG / OpenOCD to:

  • Reset and halt the cpu at PC=0
> reset halt
target halted in ARM state due to debug request, current mode: Supervisor
cpsr: 0x400000d3 pc: 0x00000000
MMU: disabled, D-Cache: disabled, I-Cache: disabled
  • Download a small piece of code for low-level SDRAM timing initialization (overwrite 4k SRAM of steppingstone)
> load_binary /space/misc/gta01/u-boot.git/board/gta01/lowlevel_foo.bin 0
downloaded 332 byte in 0s 21899us
  • Assert a break point at address 0x33f80000 (which indicates that the low-level code has finished)
> bp 0x33f80000 4 hw
breakpoint added at address 0x33f80000
  • Run the code up to the break point
> resume
Target 0 resumed
> Target 0 halted
target halted in ARM state due to breakpoint, current mode: Supervisor
cpsr: 0x600000d3 pc: 0x33f80000
MMU: disabled, D-Cache: disabled, I-Cache: enabled
  • Download the U-Boot RAM image to 0x33f80000
> load_binary /space/misc/gta01/u-boot.git/u-boot.bin 0x33f80000
downloaded 135692 byte in 6s 567264us
  • Resume processing
> resume
Target 0 resumed

At this point, the display backlight gets bright and we see the following familiar prompt on the serial console:

U-Boot 1.1.6 (Jan 13 2007 - 23:44:23)

DRAM:  128 MB
NAND:  64 MiB
*** Warning - bad CRC or NAND, using default environment

In:    serial
Out:   serial
Err:   serial
Hit any key to stop autoboot:  0
GTA01Bv2 #

Creating bootable images

U-Boot needs bootable images (such as kernels, but also initrd and others) in form of a so-called uImage. In order to create a uImage from e.g. a vmlinux kernel image, you can proceed as follows:

objcopy -O binary -R .note -R .comment -S vmlinux linux.bin
gzip -9 linux.bin
u-boot/tools/mkimage -A arm -O linux -T kernel -C gzip -a 30008000 -e 30008000 -n "Kernel Image QT2410" -d linux.bin.gz uImage

Boot menu

U-Boot boot menu on Neo1973

As of the Phase-0 release, our U-Boot version now features an on-screen boot menu. The items are defined by menu entries in the environment.

Accessing the boot menu

You can access the boot menu by pressing and holding the Neo1973 AUX Button together with the power button while switching the phone on.

Using the boot menu

By pressing the Neo1973 AUX Button you can cycle through the menu items. Use the POWER button to select one item.

U-Boot prompt

Accessing the U-Boot prompt

The U-Boot prompt is available either on the serial console (via Debug Board), or as virtual USB Serial device (USB CDC_ACM). Whether the serial port or usb is used depends on the U-Boot environment variables stdin, stdout and stderr.

Whether or not you use usbtty, the first couple of messages will always be displayed on the serial console.

The U-Boot is currently configured to wait for three seconds. If a key press on the stdin is received within those three seconds, auto-boot is aborted.

Using usbtty from Linux

Just by connecting the phone in U-Boot mode to your Linux pc should make it detect a CDC ACM device, and you should get a new tty device called /dev/ttyACM0. If not, check that module cdc_acm is loaded or CONFIG_USB_ACM=y (Device Drivers -> USB support -> USB Modem (CDC ACM) support). (Instructions for MacOS users are here)

Use your favourite terminal emulator (minicom, cu, zc, screen ...) to access it like any other serial port. Clear any modem intialisation strings (minicom).

You can adapt the instructions for USB-serial from the Mac OS page. If you don't have a favorite, try just "cu -l dev/ttyACM0". It is in the taylor-uucp package, use "apt-get install cu" if it is not yet installed

Enter Bootprompt with:

cu -l /dev/ttyACM0

You might need to

chown uucp.uucp /dev/ttyACM0

to get the necessary rights (even as root, must be done each time). For example, if cu prints "cu: /dev/ttyACM0: Line in use", then try chowning /dev/ttyACM0 to uucp.uucp; apparently cu can be pretty picky about permissions.

A nice alternative for cu is Werner Almesberger's neocon.

First, you should try to check whether the USB device shows up in 'lsusb' while you're running in U-Boot mode:

# lsusb -d 1457:5119
Bus 005 Device 079: ID 1457:5119

Note: The Neo Freerunner (GTA02) has the ID 1d50:5119

Second, let's see some more details about the available endpoints and configurations:

# lsusb -v -d 1457:5119
Bus 005 Device 079: ID 1457:5119
Device Descriptor:
bLength                18
bDescriptorType         1
bcdUSB               1.10
bDeviceClass            2 Communications
bDeviceSubClass         0
bDeviceProtocol         0
bMaxPacketSize0        16
idVendor           0x1457
idProduct          0x5119
bcdDevice            0.00
iManufacturer           1 Openmoko, Inc
iProduct                2 Neo1973 Bootloader U-Boot 1.2.0-g6c7cac8c-dirty-moko3
iSerial                 3 0000000
bNumConfigurations      1
Configuration Descriptor:
bLength                 9
bDescriptorType         2
wTotalLength           85
bNumInterfaces          3
bConfigurationValue     1
iConfiguration          4 TTY via USB
bmAttributes         0xc0
Self Powered
MaxPower                0mA
Interface Descriptor:
bLength                 9
bDescriptorType         4
bInterfaceNumber        0
bAlternateSetting       0
bNumEndpoints           1
bInterfaceClass         2 Communications
bInterfaceSubClass      2 Abstract (modem)
bInterfaceProtocol      1 AT-commands (v.25ter)
iInterface              6 Control Interface
CDC Header:
bcdCDC               0.6e
CDC Call Management:
bmCapabilities       0x00
bDataInterface          1
bmCapabilities       0x00
CDC Union:
bMasterInterface        0
bSlaveInterface         1
Endpoint Descriptor:
bLength                 7
bDescriptorType         5
bEndpointAddress     0x81  EP 1 IN
bmAttributes            3
Transfer Type            Interrupt
Synch Type               None
Usage Type               Data
wMaxPacketSize     0x0010  1x 16 bytes
bInterval             255
Interface Descriptor:
bLength                 9
bDescriptorType         4
bInterfaceNumber        1
bAlternateSetting       0
bNumEndpoints           2
bInterfaceClass        10 CDC Data
bInterfaceSubClass      0 Unused
bInterfaceProtocol      0
iInterface              5 Bulk Data Interface
Endpoint Descriptor:
bLength                 7
bDescriptorType         5
bEndpointAddress     0x02  EP 2 OUT
bmAttributes            2
Transfer Type            Bulk
Synch Type               None
Usage Type               Data
wMaxPacketSize     0x0010  1x 16 bytes
bInterval             255
Endpoint Descriptor:
bLength                 7
bDescriptorType         5
bEndpointAddress     0x83  EP 3 IN
bmAttributes            2
Transfer Type            Bulk
Synch Type               None
Usage Type               Data
wMaxPacketSize     0x0010  1x 16 bytes
bInterval             255
Interface Descriptor:
bLength                 9
bDescriptorType         4
bInterfaceNumber        2
bAlternateSetting       0
bNumEndpoints           0
bInterfaceClass       254 Application Specific Interface
bInterfaceSubClass      1 Device Firmware Update
bInterfaceProtocol      1
iInterface              7 USB Device Firmware Upgrade
Device Status:     0x0001
Self Powered

Next, you can access it using your favourite terminal program.

Then, if the environment is not set correctly, you will need to use the current console (e.g. serial console) to change the console entries in the environment:

GTA01Bv2 # setenv stderr usbtty
GTA01Bv2 # setenv stdout usbtty
GTA01Bv2 # setenv stdin usbtty

Typical U-Boot prompt

U-Boot 1.2.0-moko1 (Feb 16 2007 - 00:36:13)

DRAM:  128 MB
NAND:  64 MiB
Found Environment offset in OOB..
Video: 640x480x8 31kHz 59Hz
USB:   S3C2410 USB Deviced
In:    serial
Out:   serial
Err:   serial
Hit any key to stop autoboot:  0
GTA01Bv3 #

Commands on the U-Boot prompt

See U-Boot commands.

What if I borked my U-Boot environment and don't get a prompt anymore?

NOTE: This solution applies to a changed U-Boot environment which prevents NAND U-Boot to successfully boot. The Debian U-Boot configuration script may be a cause of this issue.

Found a solution here: [[1]]

It works the following way:

svn co http://svn.openmoko.org/trunk/src/host/devirginator cd devirginator

  • Read the U-Boot environment from the device:

dfu-util -a u-boot_env -R -U env.in

  • Create a file that contains everything you want to change in your U-Boot environment or get it by issuing the following command:

wget http://svn.openmoko.org/trunk/src/host/devirginator/environment.in

  • Now let devirginator generate a new u-boot_env partition for us, - that contains the partition table from our u-boot_env, - and all changes we wanted to make; Note that the -D GTA02 is needed for the neo FreeRunner only, and has to come before the other options.

./envedit.pl -D GTA02 -i env.in -f environment.in -o env.out

  • On my box the partition layout didn't seem to match the idea of envedit.pl, so it issued 2 warnings:

warning: environment is 262144 bytes, expected 16384 CRC error: expected 0xc33e35fc, got 0x93097bfb

  • In this case jut add an additional argument to the command line - that has to be the 1st argument, though, and that contains the size information we got from the warning:

./envedit.pl -s 262144 -D GTA02 -i env.in -f environment.in -o env.out

  • Now the perl script should produce no more output anything but write a new u-boot_env partition that we can upload to the device by:

dfu-util -a u-boot_env -R -D env.out

Device Firmware Upgrade

Our version of U-Boot also implements USB DFU. This can be useful to load files and kernel for quick testing.

To find out whether your version of U-Boot supports this, use the output of $ lsusb -v -d 1457:5119 while the phone is in u-boot mode.

If it supports DFU, you should see the following snippet towards the end of the output:

Interface Descriptor:
bLength                 9
bDescriptorType         4
bInterfaceNumber        2
bAlternateSetting       0
bNumEndpoints           0
bInterfaceClass       254 Application Specific Interface
bInterfaceSubClass      1 Device Firmware Update
bInterfaceProtocol      1
iInterface              0

For information on how to do firmware upgrades, please see dfu-util. For neo 1973 you may see Flashing the Neo 1973#Actually_flashing_things_into_the_device, and for the FreeRunner : Flashing the Neo FreeRunner.

Booting files over DFU

To load a file at memory address 0x32000000:

dfu-util -a 0 -D fileToLoad -R

After that, send 'bootm 0x32000000' to u-boot or 'bootelf 0x32000000' if its an elf file.

Simple python script that can boot an ELF image - avoiding a ACM bug that breaks on large packets.

import sys
import os
import time

cmd1 = "neo backlight off\n"
cmd2 = "bootelf 0x32000000\n"

def output(tty, str):
  for x in str:

if len(sys.argv) == 2:
  print "Loading %s..." % sys.argv[1]

  loadfile = "dfu-util -a 0 -D %s -R" % sys.argv[1]



  tty = open("/dev/ttyACM0", "a")

  output(tty, cmd1)
  output(tty, cmd2)

  print "Usage: %s elffile" % sys.argv[0]
  print ""


USB connectivity problems

I once got errors like this (in dmesg or /var/log/messages) on the host side while connecting the Neo in U-Boot:

usb 2-1: device descriptor read/64, error -110 usb usb2: Controller not stopped yet!


hub 4-0:1.0: port 1 disabled by hub (EMI?), re-enabling... usb 4-1: USB disconnect, address 2

A possible solution is given below. Please note that if you have a usb keyboard or mouse then the command might cause trouble.

rmmod uhci_hcd ; modprobe uhci_hcd

Another option is to plug the FR into a different USB port on the host, preferably one on the Motherboard not the hub.

Disconnecting the Neo's USB while powering up may prevent this problem in the future.

Related pages

See Flashing the Neo 1973 and Flashing the Neo FreeRunner for instructions on using dfu-util to install a new U-Boot in your phone.

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