1 U-Boot 1.1.4 modification for routers
7 [README w języku polskim/README in Polish language](https://github.com/pepe2k/u-boot_mod/blob/master/READMEPL.md)
9 - [Introduction](#introduction)
10 - [Supported devices](#supported-devices)
11 - [Known issues](#known-issues)
12 - [Modifications, changes](#modifications-changes)
13 - [Web server](#web-server)
14 - [Network Console](#network-console)
16 - [Supported FLASH chips](#supported-flash-chips)
17 - [How to install it?](#how-to-install-it)
18 - [Cautions, backups](#cautions-backups)
19 - [Using external programmer](#using-external-programmer)
20 - [Using UART, U-Boot console and TFTP server](#using-uart-u-boot-console-and-tftp-server)
21 - [Important notice!](#important-notice)
22 - [Step by step instruction](#step-by-step-instruction)
23 - [Using OpenWrt](#using-openwrt)
24 - [Using DD-WRT](#using-dd-wrt)
25 - [How to use it?](#how-to-use-it)
26 - [How to compile the code?](#how-to-compile-the-code)
28 - [License, outdated sources etc.](#license-outdated-sources-etc)
34 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**.
36 You can download original sources from the following pages:
38 - [TP-Link GPL Code Center](http://www.tp-link.com/en/support/gpl/ "TP-Link GPL Code Center")
39 - [D-Link GPL Source Code Support](http://tsd.dlink.com.tw/GPL.asp "D-Link GPL Source Code Support")
41 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](http://code.google.com/p/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.
43 First version of this modification was introduced on **OpenWrt** forum in [this thread](https://forum.openwrt.org/viewtopic.php?id=43237), 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.
45 You can find some information about previous versions of this project also on my [blog](http://www.tech-blog.pl), in [this article](http://www.tech-blog.pl/2013/03/29/zmodyfikowany-u-boot-dla-routerow-tp-link-z-atheros-ar9331-z-trybem-aktualizacji-oprogramowania-przez-www-i-konsola-sieciowa-netconsole/). It is in Polish, but [Google Translator](http://translate.google.com/translate?hl=pl&sl=pl&tl=en&u=http%3A%2F%2Fwww.tech-blog.pl%2F2013%2F03%2F29%2Fzmodyfikowany-u-boot-dla-routerow-tp-link-z-atheros-ar9331-z-trybem-aktualizacji-oprogramowania-przez-www-i-konsola-sieciowa-netconsole%2F&sandbox=1) will help you to understand it.
47 If you like this project, you may [buy me a beer](https://www.paypal.com/cgi-bin/webscr?cmd=_donations&business=FN3XW36YHSY2S&lc=US&item_name=For%20a%20great%20job%21¤cy_code=USD&bn=PP%2dDonationsBF%3abtn_donate_LG%2egif%3aNonHosted)!
52 Currently supported devices:
55 - 8devices Carambola 2 (for version with development board, [photos in my gallery](http://galeria.tech-blog.pl/8devices_Carambola_2/))
56 - TP-Link TL-MR3020 v1 ([photos in my gallery](http://galeria.tech-blog.pl/TPLINK_TL-MR3020/))
57 - TP-Link TL-MR3040 v1 and v2
58 - TP-Link TL-WR703N v1, ([photos in my gallery](http://galeria.tech-blog.pl/TPLINK_TL-WR703N/))
59 - TP-Link TL-WR720N v3 (version for Chinese market)
60 - TP-Link TL-WR710N v1 (version for European market, [photos in my gallery](http://galeria.tech-blog.pl/TP-Link_TL-WR710N-EU/))
61 - TP-Link TL-MR10U v1 ([photos in my gallery](http://galeria.tech-blog.pl/TP-Link_TL-MR10U/))
63 - TP-Link TL-WR740N v4 (and similar, like TL-WR741ND v4)
64 - TP-Link TL-MR3220 v2
65 - GS-Oolite/Elink EL-M150 module with dev board ([photos in my gallery](http://galeria.tech-blog.pl/Elink_EL-M150_Development-Board/))
67 - Village Telco Mesh Potato 2 (based on Dragino MS14)
68 - GL.iNet 64xxA ([photos in my gallery](http://galeria.tech-blog.pl/GLiNet/))
70 - **Atheros AR1311 (similar to AR9331)**
71 - D-Link DIR-505 H/W ver. A1 ([photos in my gallery](http://galeria.tech-blog.pl/D-Link_DIR-505/))
74 - TP-Link TL-MR3420 v2
75 - TP-Link TL-WR841N/D v8
76 - TP-Link TL-WA830RE v2
77 - TP-Link TL-WA801ND v2
80 - TP-Link TL-WDR3600 v1
81 - TP-Link TL-WDR43x0 v1
82 - TP-Link TL-WDR3500 v1
84 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**.
86 More information about supported devices:
88 | Model | SoC | FLASH | RAM | U-Boot image | U-Boot env |
89 |:--- | :--- | ---: | ---: | ---: | ---: |
90 | [8devices Carambola 2](http://8devices.com/carambola-2) | AR9331 | 16 MiB | 64 MiB DDR2 | 256 KiB | 64 KiB, R/W |
91 | [TP-Link TL-MR3020 v1](http://wiki.openwrt.org/toh/tp-link/tl-mr3020) | AR9331 | 4 MiB | 32 MiB DDR1 | 64 KiB, LZMA | RO |
92 | [TP-Link TL-MR3040 v1/2](http://wiki.openwrt.org/toh/tp-link/tl-mr3040) | AR9331 | 4 MiB | 32 MiB DDR1 | 64 KiB, LZMA | RO |
93 | [TP-Link TL-WR703N](http://wiki.openwrt.org/toh/tp-link/tl-wr703n) | AR9331 | 4 MiB | 32 MiB DDR1 | 64 KiB, LZMA | RO |
94 | [TP-Link TL-WR720N v3](http://wiki.openwrt.org/toh/tp-link/tl-wr720n) | AR9331 | 4 MiB | 32 MiB DDR1 | 64 KiB, LZMA | RO |
95 | [TP-Link TL-WR710N v1](http://wiki.openwrt.org/toh/tp-link/tl-wr710n) | AR9331 | 8 MiB | 32 MiB DDR1 | 64 KiB, LZMA | RO |
96 | [TP-Link TL-MR10U v1](http://wiki.openwrt.org/toh/tp-link/tl-mr10u) | AR9331 | 4 MiB | 32 MiB DDR1 | 64 KiB, LZMA | RO |
97 | [TP-Link TL-MR13U v1](http://wiki.openwrt.org/toh/tp-link/tl-mr13u) | AR9331 | 4 MiB | 32 MiB DDR1 | 64 KiB, LZMA | RO |
98 | [TP-Link TL-WR740N v4](http://wiki.openwrt.org/toh/tp-link/tl-wr740n) | AR9331 | 4 MiB | 32 MiB DDR1 | 64 KiB, LZMA | RO |
99 | [TP-Link TL-MR3220 v2](http://wiki.openwrt.org/toh/tp-link/tl-mr3420) | AR9331 | 4 MiB | 32 MiB DDR1 | 64 KiB, LZMA | RO |
100 | GS-Oolite/Elink EL-M150 module | AR9331 | 4/8/16 MiB | 64 MiB DDR2 | 64 KiB, LZMA | RO |
101 | [Dragino 2 (MS14)](http://wiki.openwrt.org/toh/dragino/ms14) | AR9331 | 16 MiB | 64 MiB DDR1 | 192 KiB | R/W |
102 | Village Telco Mesh Potato 2 | AR9331 | 16 MiB | 64 MiB DDR1 | 192 KiB | R/W |
103 | [GL.iNet](http://wiki.openwrt.org/toh/gl-inet/gl-inet) | AR9331 | 8/16 MiB | 64 MiB DDR1 | 64 KiB | RO |
104 | [TP-Link TL-MR3420 v2](http://wikidevi.com/wiki/TP-LINK_TL-MR3420_v2) | AR9341 | 4 MiB | 32 MiB DDR1 | 64 KiB, LZMA | RO |
105 | [TP-Link TL-WR841N/D v8](http://wiki.openwrt.org/toh/tp-link/tl-wr841nd) | AR9341 | 4 MiB | 32 MiB DDR1 | 64 KiB, LZMA | RO |
106 | [TP-Link TL-WA830RE v2](http://wikidevi.com/wiki/TP-LINK_TL-WA830RE_v2) | AR9341 | 4 MiB | 32 MiB DDR1 | 64 KiB, LZMA | RO |
107 | [TP-Link TL-WA801ND v2](http://wikidevi.com/wiki/TP-LINK_TL-WA801ND_v2) | AR9341 | 4 MiB | 32 MiB DDR1 | 64 KiB, LZMA | RO |
108 | [TP-Link TL-WDR3600 v1](http://wiki.openwrt.org/toh/tp-link/tl-wdr3600) | AR9344 | 8 MiB | 128 MiB DDR2 | 64 KiB, LZMA | RO |
109 | [TP-Link TL-WDR43x0 v1](http://wiki.openwrt.org/toh/tp-link/tl-wdr4300) | AR9344 | 8 MiB | 128 MiB DDR2 | 64 KiB, LZMA | RO |
110 | [TP-Link TL-WDR3500 v1](http://wiki.openwrt.org/toh/tp-link/tl-wdr3500) | AR9344 | 8 MiB | 128 MiB DDR2 | 64 KiB, LZMA | RO |
111 | [D-Link DIR-505 H/W ver. A1](http://wiki.openwrt.org/toh/d-link/dir-505) | AR1311 | 8 MiB | 64 MiB DDR2 | 64 KiB, LZMA | RO |
113 *(LZMA) - U-Boot binary image is compressed with LZMA.*
114 *(R/W) - environment exists in separate FLASH block which allows you to save it and keep after power down.*
115 *(RO) - environment is read only, you can change and add new variables only during runtime.*
120 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.
122 Modifications, changes
123 ----------------------
127 The most important change is an inclusion of a web server, based on **[uIP 0.9 TCP/IP stack](http://www.gaisler.com/doc/net/uip-0.9/doc/html/main.html)**. 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.
129 Web server contains 7 pages:
131 1. index.html (allows to upgrade firmware image, screenshot below)
132 2. uboot.html (allows to upgrade U-Boot image)
133 3. art.html (allows to upgrade ART image)
139 ![](http://www.tech-blog.pl/wordpress/wp-content/uploads/2013/08/uboot_mod_firmware_upgrade.jpg)
143 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: 192.168.1.1).
145 ![](http://www.tech-blog.pl/wordpress/wp-content/uploads/2013/04/u-boot_mod_for_tp-link_with_ar9331_netconsole.jpg)
147 You could also use netcat instead of Hercules utility on Mac/Linux:
149 # nc -u -p 6666 192.168.1.1 6666
157 - Unnecessary information from boot up sequence were removed
158 - FLASH chip is automatically recognized (using JEDEC ID)
159 - Ethernet MAC is set from FLASH (no more "No valid address in FLASH. Using fixed address")
160 - Automatic kernel booting can be interrupted using any key
161 - Press and hold reset button to run:
162 - Web server (min. 3 seconds)
163 - U-Boot serial console (min. 5 seconds)
164 - U-Boot network console (min. 7 seconds)
165 - Additional commands (in comparison to the default version; availability depends on router model):
178 - Overclocking and underclocking possibilities (for now, only routers with AR9331)
180 ### Supported FLASH chips
182 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.
184 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.
186 Currently supported FLASH types:
190 - Spansion S25FL032P (4 MiB, JEDEC ID: 01 0215)*
191 - Atmel AT25DF321 (4 MiB, JEDEC ID: 1F 4700)
192 - EON EN25Q32 (4 MiB, JEDEC ID: 1C 3016)*
193 - EON EN25F32 (4 MiB, JEDEC ID: 1C 3116)*
194 - Micron M25P32 (4 MiB, JEDEC ID: 20 2016)
195 - Windbond W25Q32 (4 MiB, JEDEC ID: EF 4016)
196 - Macronix MX25L320 (4 MiB, JEDEC ID: C2 2016)
200 - Spansion S25FL064P (8 MiB, JEDEC ID: 01 0216)
201 - Atmel AT25DF641 (8 MiB, JEDEC ID: 1F 4800)
202 - EON EN25Q64 (8 MiB, JEDEC ID: 1C 3017)*
203 - Micron M25P64 (8 MiB, JEDEC ID: 20 2017)
204 - Windbond W25Q64 (8 MiB, JEDEC ID: EF 4017)*
205 - Macronix MX25L64 (8 MiB, JEDEC ID: C2 2017, C2 2617)
209 - Winbond W25Q128 (16 MB, JEDEC ID: EF 4018)*
210 - Macronix MX25L128 (16 MB, JEDEC ID: C2 2018, C2 2618)
211 - Spansion S25FL127S (16 MB, JEDEC ID: 01 2018)*
215 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.
220 ### Cautions, backups
222 **You do so at your own risk!**
223 **If you make any mistake or something goes wrong during upgrade, in worst case, your router will not boot again!**
225 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):
231 This command will show you all **MTD** (Memory Technology Device) partitions:
234 dev: size erasesize name
235 mtd0: 00020000 00010000 "u-boot"
236 mtd1: 000eeb70 00010000 "kernel"
237 mtd2: 00ee1490 00010000 "rootfs"
238 mtd3: 00c60000 00010000 "rootfs_data"
239 mtd4: 00010000 00010000 "art"
240 mtd5: 00fd0000 00010000 "firmware"
243 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.
245 To backup `u-boot` partition in RAM, run:
248 cat /dev/mtd0 > /tmp/uboot_backup.bin
251 And then connect to your router using `SCP protocol` and download from `/tmp` the `uboot_backup.bin` file.
253 ### Using external programmer
255 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.
257 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.
259 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`:
262 dev: size erasesize name
263 mtd0: 00040000 00010000 "u-boot"
264 mtd1: 00010000 00010000 "u-boot-env"
265 mtd2: 00f90000 00010000 "firmware"
266 mtd3: 00e80000 00010000 "rootfs"
267 mtd4: 00cc0000 00010000 "rootfs_data"
268 mtd5: 00010000 00010000 "nvram"
269 mtd6: 00010000 00010000 "art"
272 ### Using UART, U-Boot console and TFTP server
274 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).
276 #### Important notice!
278 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)!
280 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.
282 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](http://wiki.openwrt.org/doc/hardware/port.serial) for more, detailed information.
284 #### Step by step instruction
286 1. Install and configure any **TFTP server** on your PC (on Windows, you can use [TFTP32](http://tftpd32.jounin.net)).
288 2. Set a fixed IP address on your PC (in this tutorial we will use **192.168.1.2** for the PC and **192.168.1.1** 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).
290 3. Connect USB to UART adapter to the router and start any application to communicate with it, like [PuTTY](http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html).
291 Configure adapter to use the following settings:
294 * Parity control: none
297 4. Power on the router, wait for a line like one of the following and interrupt the process of loading a kernel:
299 `Autobooting in 1 seconds` (for most **TP-Link** routers, you should enter `tpl` at this point)
300 `Hit ESC key to stop autoboot: 1` (for **8devices Carambola 2**, use `ESC` key)
301 `Hit any key to stop autoboot: 1` (for **D-Link DIR-505**, use any key)
303 5. Set `ipaddr` and `serverip` environment variables:
306 hornet> setenv ipaddr 192.168.1.1
307 hornet> setenv serverip 192.168.1.2
309 6. Check the changes:
312 hornet> printenv ipaddr
314 hornet> printenv serverip
318 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**):
321 tftpboot 0x80800000 uboot_for_tp-link_tl-mr3020.bin
325 TFTP from server 192.168.1.2; our IP address is 192.168.1.1
326 Filename 'uboot_for_tp-link_tl-mr3020.bin'.
327 Load address: 0x80800000
328 Loading: #############
330 Bytes transferred = 65536 (10000 hex)
334 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!
336 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).
338 Please, do not make any mistake with offsets and sizes during next steps!
340 9. Erase appropriate FLASH space for new U-Boot image (this command will remove default U-Boot image!):
343 hornet> erase 0x9F000000 +0x10000
345 First 0x0 last 0x0 sector size 0x10000
350 10. Now your router does not have U-Boot, so do not wait and copy to FLASH the new one, stored earlier in RAM:
353 hornet> cp.b 0x80800000 0x9F000000 0x10000
355 Copy to Flash... write addr: 9f000000
359 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):
362 hornet> md 0x9F000000
364 9f000000: 100000ff 00000000 100000fd 00000000 ................
365 9f000010: 10000222 00000000 10000220 00000000 ..."....... ....
366 9f000020: 1000021e 00000000 1000021c 00000000 ................
367 9f000030: 1000021a 00000000 10000218 00000000 ................
368 9f000040: 10000216 00000000 10000214 00000000 ................
369 9f000050: 10000212 00000000 10000210 00000000 ................
370 9f000060: 1000020e 00000000 1000020c 00000000 ................
371 9f000070: 1000020a 00000000 10000208 00000000 ................
372 9f000080: 10000206 00000000 10000204 00000000 ................
373 9f000090: 10000202 00000000 10000200 00000000 ................
374 9f0000a0: 100001fe 00000000 100001fc 00000000 ................
375 9f0000b0: 100001fa 00000000 100001f8 00000000 ................
376 9f0000c0: 100001f6 00000000 100001f4 00000000 ................
377 9f0000d0: 100001f2 00000000 100001f0 00000000 ................
378 9f0000e0: 100001ee 00000000 100001ec 00000000 ................
379 9f0000f0: 100001ea 00000000 100001e8 00000000 ................
382 12. If you are sure that everything went OK, you may reset the board:
390 1. Compile and flash OpenWrt with an unlocked U-Boot partition.
391 - This is done by removing the `MTD_WRITEABLE` from the `mask_flags` of the `u-boot` partition.
392 - To put it simply, for TP-Link products, just remove [this line](https://dev.openwrt.org/browser/trunk/target/linux/ar71xx/files/drivers/mtd/tplinkpart.c?rev=41580#L152), compile and flash the image as usual.
393 2. Find out which mtd partition is the `u-boot` partition:
396 root@OpenWrt:/tmp/uboot-work# cat /proc/mtd
397 dev: size erasesize name
398 mtd0: 00020000 00010000 "u-boot"
399 mtd1: 000feba0 00010000 "kernel"
400 mtd2: 002d1460 00010000 "rootfs"
401 mtd3: 00100000 00010000 "rootfs_data"
402 mtd4: 00010000 00010000 "art"
403 mtd5: 003d0000 00010000 "firmware"
406 3. Transfer the new U-Boot image to the device:
409 me@laptop:~# scp uboot_for_tp-link_tl-mr3220_v2.bin root@192.168.1.1:/tmp/
410 uboot_for_tp-link_tl-mr3220_v2.bin 100% 64KB 64.0KB/s 00:00
413 4. Verify the MD5 sum of the image:
416 me@laptop:~# md5sum uboot_for_tp-link_tl-mr3220_v2.bin
417 cefad12aa9fbd04291652dae3eb7650c uboot_for_tp-link_tl-mr3220_v2.bin
419 root@OpenWrt:/tmp# md5sum uboot_for_tp-link_tl-mr3220_v2.bin
420 cefad12aa9fbd04291652dae3eb7650c uboot_for_tp-link_tl-mr3220_v2.bin
423 5. Take a backup of the current u-boot partition (`mtd0`):
426 root@OpenWrt:/tmp# dd if=/dev/mtd0 of=uboot_orig.bin
431 6. Transfer the backup off the device and to a safe place:
434 me@laptop:~# scp root@192.168.1.1:/tmp/uboot_orig.bin .
435 uboot_orig.bin 100% 128KB 128.0KB/s 00:00
438 7. **Beware**: This step may differ for other devices. I'm using TP-Link TL-MR3220v2 and it uses the first 64 KiB block to store compressed U-Boot image. In the second 64 KiB block they store additional information like MAC address, model number and WPS pin number. This means the old backup is bigger than the new one we're going to flash. To store the old settings we're going to modify only the compressed U-Boot image and leave the additional information intact. To do that, take a copy of the original file, and copy the new image over it without truncating the leftover bytes:
441 root@OpenWrt:/tmp# cp uboot_orig.bin uboot_new.bin
442 root@OpenWrt:/tmp# dd if=uboot_for_tp-link_tl-mr3220_v2.bin of=uboot_new.bin conv=notrunc
447 9. **Danger**: This is the point of no return, if you have any errors or problems, please revert the original image at any time using:
450 root@OpenWrt:/tmp# mtd write uboot_orig.bin "u-boot"
453 Writing from uboot_orig.bin to u-boot ...
456 10. Now, to actually flash the new image, run:
459 root@OpenWrt:/tmp# mtd write uboot_new.bin "u-boot"
462 Writing from uboot_new.bin to u-boot ...
465 11. To verify that the image was flashed correctly, you should verify it:
468 root@OpenWrt:/tmp# mtd verify uboot_new.bin "u-boot"
469 Verifying u-boot against uboot_new.bin ...
470 a80c3a8683345a3fb311555c5d4194c5 - u-boot
471 a80c3a8683345a3fb311555c5d4194c5 - uboot_new.bin
475 12. To restart with the new bootloader, reboot the router:
478 root@OpenWrt:/tmp# reboot
490 How to compile the code?
491 ------------------------
493 You can use one of the free toolchains:
495 - [Sourcery CodeBench Lite Edition for MIPS GNU/Linux](https://sourcery.mentor.com/GNUToolchain/subscription3130?lite=MIPS),
496 - [OpenWrt Toolchain for AR71xx MIPS](http://downloads.openwrt.org/attitude_adjustment/12.09/ar71xx/generic/OpenWrt-Toolchain-ar71xx-for-mips_r2-gcc-4.6-linaro_uClibc-0.9.33.2.tar.bz2),
497 - [ELDK (Embedded Linux Development Kit)](ftp://ftp.denx.de/pub/eldk/),
500 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.
502 All you need to do, after choosing a toolchain, is to modify [Makefile](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](Makefile):
505 export BUILD_TOPDIR=$(PWD)
506 export STAGING_DIR=$(BUILD_TOPDIR)/tmp
508 export MAKECMD=make --silent ARCH=mips CROSS_COMPILE=mips-openwrt-linux-uclibc-
509 export PATH:=$(BUILD_TOPDIR)/toolchain/bin/:$(PATH)
512 To build image, run `make model` inside top dir, for example, command:
518 will start building U-Boot image for **TP-Link TL-WR703N**.
523 #### 1. My device is not supported, but has the same hardware as one in the list, can I use this modification?
525 *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.*
527 *You can try, but remember that you are doing this only at your own risk!*
529 #### 2. I want to overclock my router, how can I do this?
531 *Currently, this option is available only for routers with Atheros AR9331 (please, look at [ap121.h](u-boot/include/configs/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.*
533 *And again, remember that you are doing this only at your own risk!*
535 #### 3. Do you test all prebuilt images before you publish them?
537 *No, because I do not have all supported devices, only few of them. But, I make tests for every supported SoC types.*
539 #### 4. I would like you to add support for device X.
541 *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.*
543 #### 5. My device does not boot after upgrade!
545 *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.*
547 License, outdated sources etc.
548 ------------------------------
550 **[U-Boot](http://www.denx.de/wiki/U-Boot/WebHome "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.
552 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.
557 - Thanks to *pupie* from OpenWrt forum for his great help
558 - Thanks for all donators and for users who contributed in code development