Backing up the Netfaster WLAN 3 firmware

The Netfaster WLAN 3 is an ADSL modem/router provided by greek ISP Hellas Online. Internally the device is identified as AR7505SW11 7-A-LIC and built around the following hardware:

Type	Part	Notes
CPU	Lantiq PSB 50601 HL v1.2	133/266 MHz
Flash	Macronix (MXIC) MX25L1606E M2	2 MB, SPI, 200mil 8-SOP
RAM	Winbond W9812G6JH-6	16MB @ 166 MHz
Switch	Lantiq PSB 6970V v1.3
WiFi	Atheros AR9271-ALJA

The admin page of this modem will not give you the option to backup the firmware the device is running (you can only backup your configuration), and you won’t be able to find it anywhere on the internet either, which means that if you accidentally erase or in any way corrupt the firmware, you won’t have a clean, working version to restore. The purpose of this post is to show you how you can get this backup.

Serial Connection

To get the firmware backup we first need to connect to the modem’s serial port. To implement this connection you’ll need a USB-to-UART serial converter such as this one.

The modem board and the serial port are pictured below. (Note you will need to do a little soldering in order to use the serial port).

The Netfaster WLAN 3 PCB. The serial port pin positions are shown.

Assuming you have the USB-to-UART converter I mentioned above or similar, with the modem powered off, implement a straight connection between converter and serial port:

• Converter GND to modem GND (pin 4)
• Converter Rx to modem Rx (pin 3)
• Converter Tx to modem Tx (pin 2)

Do not power on the modem yet. Launch your preferred terminal emulator (I’ll be using PuTTY in this post) and point it to the serial line (/dev/ttyUSB0 in my case). Set connection speed 115200, data bits 8, parity None, stop bits 1 (8N1) and open the connection.

PuTTY serial connection settings.

Note: For PuTTY to be able to open /dev/ttyUSB0 on Ubuntu you need to run it as root. To do so, open a command terminal and enter gksudo putty & .

With the PuTTY connection opened power on the modem. You will receive the following output:

ROM VER: 1.2.0
CFG 04
EEPROM Data OK

=========================================================================
Wireless ADSL Gateway AMAZON_SE Loader 7505.03 build Sep 20 2010 11:36:23
                      Arcadyan Technology Corporation
=========================================================================
SPI FLASH
RDID: c22015

Copying boot params.....DONE

Press Space Bar 3 times to enter command mode ...

Immediately press spacebar 3 times. This will halt the boot process and take you to the bootloader prompt. At the bootloader prompt press ! to enter administrator mode.

Press Space Bar 3 times to enter command mode ...123
Yes, Enter command mode ...

[AMAZON_SE Boot]:!

Enter Administrator Mode !

Once you enter administrator mode close PuTTY but do not disconnect the modem from the converter. To perform the backup we will use a different program called ‘brntool’. You can download brntool from https://github.com/rvalles/brntool.

Performing the Backup

Before running brntool we need to make a few modifications to its code, so that it is compatible with this modem. Open brntool.py with a text editor and comment-out lines 22-23, 29-31 and 59-60 by inserting a ‘#’ at the beginning of each line. Conversely, uncomment line 58 and, optionally, change the value of bs to 2048 or to any other number you prefer, as long as it is less than 10000 (bs denotes the number of bytes the program will read at a time). In the screenshots below I’ve set bs to 2048.

Comment-out lines 22-23, 29-31 and 59-60. Uncomment line 58 and, optionally, change bs to 2048.

With the changes detailed above completed, the modem at the administrative bootloader prompt and PuTTY closed, open a command terminal and run brntool by issuing the following command:

$sudo ./brntool.py --read=fw.bin --addr=0x0 --verbose --size=0x200000

If all has gone well you should see a series of dots appear as the firmware is being read. Each ‘.’ represents a successful read of ‘bs’ bytes. A ‘!’ means the read attempt failed, and the program will retry until the read succeeds. When reading is complete, the firmware will be saved as ‘fw.bin’. I recommend you perform a second backup and then compare the two backups to make sure no errors occurred (for example, in my case, the Rx pin had come loose after some point, and I only found out when I performed two successive backups and compared them; the loose Rx pin was distorting the output, so each new backup differed from the previous one).

For your reference I have uploaded my backup to http://1drv.ms/1uYcBn9 .

If you followed the instructions above you should now have a backup of the Netfaster WLAN 3 firmware. In my next post I’ll show you how to restore the firmware to the modem.

If you have any questions or if you spotted any errors or omissions, please leave me a comment.

• Backup
• Modem
• Netfaster
• Router