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U-Boot 1.1.4 modification for routers
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U-Boot 1.1.4 modification for routers

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README w języku polskim/README in Polish language


In short, this project is a deep modification of U-Boot 1.1.4 sources, mostly from TP-Link, but some code fragments were taken also from D-Link.

You can download original sources from the following pages:

The concept for this project came from another U-Boot modification, dedicated to a small and very popular TP-Link router - model TL-WR703N, which includes web fail safe mode: wr703n-uboot-with-web-failsafe. I was using it and decided to make my own version, which could have some improvements, additional capabilities, support for different models and work with all modern web browsers.

First version of this modification was introduced on OpenWrt forum in this thread, at the end of March 2013 and was dedicated only for TP-Link routers with Atheros AR9331 SoC. Now, it supports also models from different manufacturers, devices with Atheros AR934x (like TP-Link TL-WDR3600, TL-WDR43x0, TL-WR841N/D v8, TL-WA830RE v2) and other (in the near future Qualcomm Atheros QCA955x) are under development.

You can find some information about previous versions of this project also on my blog, in this article. It is in Polish, but Google Translator will help you to understand it.

If you like this project, you may buy me a beer!

Supported devices

Currently supported devices:

  • Atheros AR9331:

  • Atheros AR1311 (similar to AR9331)

  • Atheros AR9341:

    • TP-Link TL-MR3420 v2
    • TP-Link TL-WR841N/D v8
    • TP-Link TL-WA830RE v2
    • TP-Link TL-WA801ND v2
  • Atheros AR9344:

    • TP-Link TL-WDR3600 v1
    • TP-Link TL-WDR43x0 v1
    • TP-Link TL-WDR3500 v1

I tested this modification on most of these devices, with OpenWrt and OFW firmware. If you are not sure about the version of your device, please contact with me before you try to make an upgrade. Changing bootloader to a wrong version will probably damage your router and you will need special hardware to fix it, so please, be very careful.

More information about supported devices:

Model SoC FLASH RAM U-Boot image U-Boot env
8devices Carambola 2 AR9331 16 MiB 64 MiB DDR2 256 KiB 64 KiB, R/W
TP-Link TL-MR3020 v1 AR9331 4 MiB 32 MiB DDR1 64 KiB, LZMA RO
TP-Link TL-MR3040 v1/2 AR9331 4 MiB 32 MiB DDR1 64 KiB, LZMA RO
TP-Link TL-WR703N AR9331 4 MiB 32 MiB DDR1 64 KiB, LZMA RO
TP-Link TL-WR720N v3 AR9331 4 MiB 32 MiB DDR1 64 KiB, LZMA RO
TP-Link TL-WR710N v1 AR9331 8 MiB 32 MiB DDR1 64 KiB, LZMA RO
TP-Link TL-MR10U v1 AR9331 4 MiB 32 MiB DDR1 64 KiB, LZMA RO
TP-Link TL-MR13U v1 AR9331 4 MiB 32 MiB DDR1 64 KiB, LZMA RO
TP-Link TL-WR740N v4 AR9331 4 MiB 32 MiB DDR1 64 KiB, LZMA RO
TP-Link TL-MR3220 v2 AR9331 4 MiB 32 MiB DDR1 64 KiB, LZMA RO
GS-Oolite/Elink EL-M150 module AR9331 4/8/16 MiB 64 MiB DDR2 64 KiB, LZMA RO
Dragino 2 (MS14) AR9331 16 MiB 64 MiB DDR1 192 KiB R/W
TP-Link TL-MR3420 v2 AR9341 4 MiB 32 MiB DDR1 64 KiB, LZMA RO
TP-Link TL-WR841N/D v8 AR9341 4 MiB 32 MiB DDR1 64 KiB, LZMA RO
TP-Link TL-WA830RE v2 AR9341 4 MiB 32 MiB DDR1 64 KiB, LZMA RO
TP-Link TL-WA801ND v2 AR9341 4 MiB 32 MiB DDR1 64 KiB, LZMA RO
TP-Link TL-WDR3600 v1 AR9344 8 MiB 128 MiB DDR2 64 KiB, LZMA RO
TP-Link TL-WDR43x0 v1 AR9344 8 MiB 128 MiB DDR2 64 KiB, LZMA RO
TP-Link TL-WDR3500 v1 AR9344 8 MiB 128 MiB DDR2 64 KiB, LZMA RO
D-Link DIR-505 H/W ver. A1 AR1311 8 MiB 64 MiB DDR2 64 KiB, LZMA RO

(LZMA) - U-Boot binary image is compressed with LZMA.
(R/W) - environment exists in separate FLASH block which allows you to save it and keep after power down. (RO) - environment is read only, you can change and add new variables only during runtime.

Known issues

Current release is not loading kernel from some versions of TP-Link's official firmware. If you want to use the so-called OFW in any of supported TP-Link's router, do not use this modification. I am working on a solution for this issue.

Modifications, changes

Web server

The most important change is an inclusion of a web server, based on uIP 0.9 TCP/IP stack. It allows to upgrade firmware, U-Boot and ART (Atheros Radio Test) images, directly from your web browser, without need to access serial console and running a TFTP server. You can find similar firmware recovery mode, also based on uIP 0.9 TCP/IP stack, in D-Link routers.

Web server contains 7 pages:

  1. index.html (allows to upgrade firmware image, screenshot below)
  2. uboot.html (allows to upgrade U-Boot image)
  3. art.html (allows to upgrade ART image)
  4. flashing.html
  5. 404.html
  6. fail.html
  7. style.css

Network Console

Second, very useful modification is a network console (it is a part of original U-Boot sources, but none of the manufacturers included it). It allows you to communicate with U-Boot console over the Ethernet, using UDP protocol (default UDP port: 6666, router IP:



  • Faster boot up
  • Unnecessary information from boot up sequence were removed
  • FLASH chip is automatically recognized (using JEDEC ID)
  • Ethernet MAC is set from FLASH (no more "No valid address in FLASH. Using fixed address")
  • Automatic kernel booting can be interrupted using any key
  • Press and hold reset button to run:
    • Web server (min. 3 seconds)
    • U-Boot serial console (min. 5 seconds)
    • U-Boot network console (min. 7 seconds)
  • Additional commands (in comparison to the default version; availability depends on router model):
    • httpd
    • printmac
    • setmac
    • printmodel
    • printpin
    • startnc
    • startsc
    • eraseenv
    • ping
    • dhcp
    • sntp
    • iminfo
  • Overclocking and underclocking possibilities (for now, only routers with AR9331)

Supported FLASH chips

FLASH type detection may be very useful for people who has exchanged the FLASH chip in their routers. You will not need to recompile U-Boot sources, to have access to overall FLASH space in U-Boot console.

If you use FLASH type which is not listed below, this version of U-Boot will use default size for your router and, in most supported models, updating the ART image will not be available.

Currently supported FLASH types:

4 MiB:

  • Spansion S25FL032P (4 MiB, JEDEC ID: 01 0215)*
  • Atmel AT25DF321 (4 MiB, JEDEC ID: 1F 4700)
  • EON EN25Q32 (4 MiB, JEDEC ID: 1C 3016)*
  • EON EN25F32 (4 MiB, JEDEC ID: 1C 3116)*
  • Micron M25P32 (4 MiB, JEDEC ID: 20 2016)
  • Windbond W25Q32 (4 MiB, JEDEC ID: EF 4016)
  • Macronix MX25L320 (4 MiB, JEDEC ID: C2 2016)

8 MiB:

  • Spansion S25FL064P (8 MiB, JEDEC ID: 01 0216)
  • Atmel AT25DF641 (8 MiB, JEDEC ID: 1F 4800)
  • EON EN25Q64 (8 MiB, JEDEC ID: 1C 3017)*
  • Micron M25P64 (8 MiB, JEDEC ID: 20 2017)
  • Windbond W25Q64 (8 MiB, JEDEC ID: EF 4017)*
  • Macronix MX25L64 (8 MiB, JEDEC ID: C2 2017, C2 2617)
  • SST 25VF064C (8 MiB, JEDEC ID: BF 254B)

16 MiB:

  • Winbond W25Q128 (16 MB, JEDEC ID: EF 4018)*
  • Macronix MX25L128 (16 MB, JEDEC ID: C2 2018, C2 2618)
  • Spansion S25FL127S (16 MB, JEDEC ID: 01 2018)*

(*) tested

If you want to use other type, please contact with me or make changes in the code, test them and send a pull request or a patch.

How to install it?

Cautions, backups

You do so at your own risk!
If you make any mistake or something goes wrong during upgrade, in worst case, your router will not boot again!

It is a good practice to backup your original U-Boot image/partition (especially for TP-Link devices) before you make any changes. For example, using OpenWrt (TP-Link TL-WR703N with 16 MiB FLASH):

cat /proc/mtd

This command will show you all MTD (Memory Technology Device) partitions:

dev:    size   erasesize  name
mtd0: 00020000 00010000 "u-boot"
mtd1: 000eeb70 00010000 "kernel"
mtd2: 00ee1490 00010000 "rootfs"
mtd3: 00c60000 00010000 "rootfs_data"
mtd4: 00010000 00010000 "art"
mtd5: 00fd0000 00010000 "firmware"

As you can see, u-boot partition size is 0x20000 (128 KiB) and my image for this model has size of 0x10000 (64 KiB) - it is a very important difference! You should remember about this if you want to use mtd utility, to change U-Boot.

To backup u-boot partition in RAM, run:

cat /dev/mtd0 > /tmp/uboot_backup.bin

And then connect to your router using SCP protocol and download from /tmp the uboot_backup.bin file.

Using external programmer

If you have an external FLASH programmer (all supported devices have SPI NOR FLASH chips), you probably know how to use it. Download package with prebuilt images or compile the code, choose right file for your device and put it on FLASH at the beginning (offset 0x00000). Remember to first erase block(s) - with high probability, if you use some kind of automatic mode, the programmer will do it for you.

All prebuilt images are padded with 0xFF, so their size will always be a multiple of 64 KiB block and they will not be bigger than the original versions. For example, TP-Link uses only first 64 KiB block to store compressed U-Boot image (in most of their modern devices). In the second 64 KiB block they store additional information like MAC address, model number and WPS pin number.

On the other hand, U-Boot image in Carambola 2 from 8devices may have up to 256 KiB (4x 64 KiB block), they use uncompressed version and environment stored in FLASH. Immediately after the Carambola 2 U-Boot partition is an area which contains U-Boot environment variables (1x 64 KiB block), called u-boot-env:

dev:    size   erasesize  name
mtd0: 00040000 00010000 "u-boot"
mtd1: 00010000 00010000 "u-boot-env"
mtd2: 00f90000 00010000 "firmware"
mtd3: 00e80000 00010000 "rootfs"
mtd4: 00cc0000 00010000 "rootfs_data"
mtd5: 00010000 00010000 "nvram"
mtd6: 00010000 00010000 "art"

Using UART, U-Boot console and TFTP server

It is probably the most common method to change firmware in case of any problems. Main disadvantage of this approach is the need to connect with device using a serial port (this does not apply to Carambola 2 with development board, which already has a built-in USB-UART adapter, based on FTDI FT232RQ).

Important notice!

All these devices have an UART interface integrated inside the SoC, which operates at TTL 3.3 V (in fact, GPIO pins can work at this voltage, but their real range is < 3 V)!

Please, do not connect any RS232 +/- 12 V cable or any adapter without logic level converter, because it may damage your device. It would be the best if you use any USB to UART adapter with integrated 3.3 V logic level converter. And please, remember that you should connect only RX, TX and GND signals. DO NOT connect together 3.3 V signals from router and from adapter if you do not know what are you doing, because you may burn out your adapter and/or router! Connect the adapter using USB port in your PC and router with original power supply.

For a long time I have been using without any problems a small and very cheap (about 1-2 USD) CP2102 based adapter. Go to Serial Console article in OpenWrt Wiki for more, detailed information.

Step by step instruction

  1. Install and configure any TFTP server on your PC (on Windows, you can use TFTP32).

  2. Set a fixed IP address on your PC (in this tutorial we will use for the PC and for the router) and connect it to the router, using RJ45 network cable (in most case you will need to use one of the available LAN ports, but WAN port should also work).

  3. Connect USB to UART adapter to the router and start any application to communicate with it, like PuTTY.
    Configure adapter to use the following settings:

    • Baud rate: 115200
    • Data bits: 8
    • Parity control: none
    • Stop bits: 1
    • Handshaking: none
  4. Power on the router, wait for a line like one of the following and interrupt the process of loading a kernel:

    Autobooting in 1 seconds (for most TP-Link routers, you should enter tpl at this point)
    Hit ESC key to stop autoboot: 1 (for 8devices Carambola 2, use ESC key)
    Hit any key to stop autoboot: 1 (for D-Link DIR-505, use any key)

  5. Set ipaddr and serverip environment variables:

    hornet> setenv ipaddr
    hornet> setenv serverip
  6. Check the changes:

    hornet> printenv ipaddr
    hornet> printenv serverip
  7. Download and store in RAM proper image for your router, using tftpboot command in U-Boot console (in this example, for TP-Link TL-MR3020):

    tftpboot 0x80800000 uboot_for_tp-link_tl-mr3020.bin
    eth1 link down
    Using eth0 device
    TFTP from server; our IP address is
    Filename 'uboot_for_tp-link_tl-mr3020.bin'.
    Load address: 0x80800000
    Loading: #############
    Bytes transferred = 65536 (10000 hex)
  8. Next step is very risky! You are going to delete existing U-Boot image from FLASH in your device and copy from RAM the new one. If something goes wrong (for example, a power failure), your router, without bootloader, will not boot again!

    You should also note the size of downloaded image. For supported TP-Link and D-Link routers it will be always 0x10000 (64 KiB), but for Carambola 2 image size is different: 0x40000 (256 KiB). In all cases, the start address of FLASH is 0x9F000000 and for RAM: 0x80000000 (as you may noticed, I did not use start address of RAM to store image and you should follow this approach).

    Please, do not make any mistake with offsets and sizes during next steps!

  9. Erase appropriate FLASH space for new U-Boot image (this command will remove default U-Boot image!):

    hornet> erase 0x9F000000 +0x10000   
    First 0x0 last 0x0 sector size 0x10000
    Erased 1 sectors
  10. Now your router does not have U-Boot, so do not wait and copy to FLASH the new one, stored earlier in RAM:

    hornet> cp.b 0x80800000 0x9F000000 0x10000   
    Copy to Flash... write addr: 9f000000
  11. If you want, you can check content of the newly written FLASH and compare it to the image on your PC (or better also do such a "legit memory content" comparison prior to writing!), using md command in U-Boot console, which prints indicated memory area (press only ENTER after first execution of this command to move further in memory):

    hornet> md 0x9F000000
    9f000000: 100000ff 00000000 100000fd 00000000    ................
    9f000010: 10000222 00000000 10000220 00000000    ..."....... ....
    9f000020: 1000021e 00000000 1000021c 00000000    ................
    9f000030: 1000021a 00000000 10000218 00000000    ................
    9f000040: 10000216 00000000 10000214 00000000    ................
    9f000050: 10000212 00000000 10000210 00000000    ................
    9f000060: 1000020e 00000000 1000020c 00000000    ................
    9f000070: 1000020a 00000000 10000208 00000000    ................
    9f000080: 10000206 00000000 10000204 00000000    ................
    9f000090: 10000202 00000000 10000200 00000000    ................
    9f0000a0: 100001fe 00000000 100001fc 00000000    ................
    9f0000b0: 100001fa 00000000 100001f8 00000000    ................
    9f0000c0: 100001f6 00000000 100001f4 00000000    ................
    9f0000d0: 100001f2 00000000 100001f0 00000000    ................
    9f0000e0: 100001ee 00000000 100001ec 00000000    ................
    9f0000f0: 100001ea 00000000 100001e8 00000000    ................
  12. If you are sure that everything went OK, you may reset the board:

    hornet> reset

Using OpenWrt


Using DD-WRT


How to use it?


How to compile the code?

You can use one of the free toolchains:

I am using Sourcery CodeBench Lite Edition for MIPS GNU/Linux on Ubuntu 12.04 LTS (32-bit, virtual machine) and all released binary images were/will be built using this set.

All you need to do, after choosing a toolchain, is to modify Makefile - change or remove export MAKECMD and if needed add export PATH. For example, to use OpenWrt Toolchain instead of Sourcery CodeBench Lite, download it and extract into toolchain folder, inside the top dir and change first lines in Makefile:


export MAKECMD=make --silent ARCH=mips CROSS_COMPILE=mips-openwrt-linux-uclibc-
export PATH:=$(BUILD_TOPDIR)/toolchain/bin/:$(PATH)

To build image, run make model inside top dir, for example, command:

make tplink_wr703n

will start building U-Boot image for TP-Link TL-WR703N.


1. My device is not supported, but has the same hardware as one in the list, can I use this modification?

It could be dangerous! I know that a lot of routers uses the same hardware - for example, TP-Link has a battery powered routers set, which contains: TL-MR10U, TL-MR11U (TL-MR3040 in Europe) TL-MR12U and TL-MR13U. All of them has the same platform: Atheros AR9331 with 32 MiB of DDR RAM and 4 MiB of SPI NOR FLASH. But, there may exist a slight difference, like GPIO pin number for reset button or LED(s), that may cause problems.

You can try, but remember that you are doing this only at your own risk!

2. I want to overclock my router, how can I do this?

Currently, this option is available only for routers with Atheros AR9331 (please, look at ap121.h file which contains all information about PLL register configuration and an untypical clocks for CPU, RAM and AHB). What more, you will need to compile the code yourself, because I will not publish images with non-default clocks.

And again, remember that you are doing this only at your own risk!

3. Do you test all prebuilt images before you publish them?

No, because I do not have all supported devices, only few of them. But, I make tests for every supported SoC types.

4. I would like you to add support for device X.

You can do it yourself and send me a pull request or a patch. If you do not want to, or do not know how to do it, please contact with me directly.

5. My device does not boot after upgrade!

I told you... bootloader, in this case U-Boot, is the most important piece of code inside your device. It is responsible for hardware initialization and booting an OS (kernel in this case), i.e. it's the bridge head for delegating to / flashing kernel and rootfs images. So, if during the upgrade something went wrong, your device will not boot any more. The only way to recover from such a situation in a mild way is via a JTAG adapter connection. In case of a lack of JTAG connection, you would even need to remove the FLASH chip, load proper image using an external programmer and solder it back.

License, outdated sources etc.

U-Boot project is Free Software, licensed under version 2 of the GNU General Public License. All information about license, contributors etc., are included with sources, inside u-boot folder.

You should know, that most routers, especially those based on Atheros SoCs, uses very old versions of U-Boot (1.1.4 is from 2005/2006). So, these sources are definitely outdated (do not even try to merge them with official release), but it was easier for me to modify them, than move TP-Link/Atheros changes to the current version. Moreover, lot of unnecessary code fragments and source files were removed for ease of understanding the code.


  • Thanks to pupie from OpenWrt forum for his great help
  • Thanks for all donators and for users who contributed in code development
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