The installation procedure is almost the same as for D-Link DSL-524T, so use the link above for the full installation procedure.
The main differences are:
Both username and password for ADAM2 bootloader are adam2, not ADAM2. The bootloader of my device listens by default on port 18.104.22.168 at startup.
Flashing router on Linux (kernel 2.6.35-24) was EXTREMELY slow. (Put “debug” command before “put …” command during installation procedure and you may see.) I tried Windows 7 Home edition, but a connection error appeared. At last, FTP client in Windows XP Professional did the job - it took only about 3 minutes to put the firmware on the router. So I recommend you to use this OS, but I hope that it is an issue of my device or someone will find another way to do a sucessful flash.
I use Backfire 10.03.1-rc4 and it works like a charm – it's uptime is in weeks. My unit has been modified by adding heatsinks on chips.
Changing Annex A to Annex B
If you use generic firmware “openwrt-ar7-squashfs.bin”, you may have to add Annex B support to it - it contains only Annex A module. However, it is very easy to do this job: find a package with “kmod-sangam-atm-annex-b” in its name in /package subdirectory of the release you have used. On your router, remove original “kmod-sangam-atm-annex-a” package (using opkg or web interface) and activate dropbear-sshd - telnet into your router and insert new root password using passwd command. Then put “annex-b” package to your router by scp and install it using opkg.