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Return to U-Boot.

Personal tools

u-boot menu on Neo1973
u-boot splash screen on Neo1973

The bootloader on the Neo1973, U-Boot, takes care of device functionality until Openmoko is booted. This includes USB DFU for flashing Openmoko, a splash screen, a boot menu, a console for bootloader commands, configuration via bootloader environment, and loading a kernel.

There are various bootloader versions available.

Phase0 Quick Start

  • Make sure that your phone has had the battery and USB cable removed for at least 30 seconds.
  • Connect the Neo (ie not Debug Board) to a Linux host with the USB cable.
  • Hold in the AUX button on power-up to access the boot menu.
  • 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 )
  • 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 bootloader prompt.
  • Set the bootdelay uboot environment variable to -1 if you want it to always halt at the bootloader on power-up.


The GTA01 uses the u-boot bootloader.

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.

Bootloader source code

The current bootloader patches can be found at

Untar the sources, apply the patch, run "make gta01bv3_config" (or gta01bv2_config, or whatever hardware revision you have), run "make". You will get a resulting "u-boot.bin" image, which you can directly flash (either using existing bootloader or sjf2410-linux) into NAND.

Bootloader binary

The latest bootloader binary builds can be found under in the subdirectory 200X.XX/images/. It should be written to the NAND flash address 0x00000000 (size 0x30000) (the first partition).

Bootloader development


If you want to do bootloader development on the QT2410, it's easier to work with a bootloader 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.


Doing bootloader development on the GTA01 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


The first block holds a little 4KByte RAM buffer that is auto-filled from NAND by CPU hardware, called "steppingstone" when we boot from NAND, or the NOR is mapped in there.

nCS0: 00000000 07FFFFFF 4K steppingstone or NOR (Aux held down)
nCS1: 08000000 0FFFFFFF Glamo
nCS2: 10000000 17FFFFFF nothing mapped
nCS3: 18000000 1FFFFFFF NOR
nCS4: 20000000 17FFFFFF nothing mapped
nCS5: 28000000 2FFFFFFF nothing mapped
nCS6: 30000000 37FFFFFF on-MCP SDRAM 128MB
nCS7: 38000000 3FFFFFFF external SDRAM 128MB

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.

Bootloader prompt

Accessing the bootloader prompt

The bootloader 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 bootloader 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, enable the CONFIG_USB_ACM (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. If you don't have a favorite, try just: (cu is in the taylor-uucp package, use "apt-get install cu" if it is not yet installed)

cu -l /dev/ttyACM0

You might need to

chown uucp.uucp /dev/ttyACM0

to get the necessary rights (even as root).

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  

Second, lets 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
      CDC ACM:
        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 bootloader prompt

See bootloader commands.

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.

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!

The problem disappeared at least for me by the command below on the host side. Please note that if you have usb keyboard or mouse then the command might cause trouble.. I only have PS/2 so I couldn't test it.

rmmod uhci_hcd ; modprobe uhci_hcd

I also got this error a few times, I was able to fix it by plugging the FR into a different USB port on my host, preferably one on the Motherboard not the hub.

See Flashing Openmoko