OpenWRT backfire 10.03 b43 (wrt54g) drivers mods

Introduction

This modification might be illegal in your country. You can use router with this modification only if you have amateur radio license. You cannot use encryption and you need to make sure your callsign is present inside packets transmitted.

The goal is to modify OpenWRT Backfire 10.03 broadcom b43 (Linksys WRT54G(LS) drivers) to make router work outside of ISM standard WiFi channels on 13 cm amateur band (channels 0 and probably -1, -2 if possible) and try to setup a link between two routers using one of Mesh network frameworks.

By using legacy 11 MHz channel width mode and work on channel 0, 2407 MHz router will be still within ISM band, it won’t be visible by causal access points and at the same it will be within 13 cm amateur band, thus can be used legally with directional antennas and higher E.I.R.P. (maximum allowed is mostly 100 mW).

Userful read

OpenWRT documentation and other useful links:

• IARU 1 13cm band plan - https://www.iaru-r1.org/wp-content/uploads/2020/03/UHF-Bandplan.pdf
• WRT54G – https://wiki.openwrt.org/toh/linksys/wrt54g
• Build system installation – https://wiki.openwrt.org/doc/howto/buildroot.exigence
• Broadband Hamnet – http://www.broadband-hamnet.org/
• Hamnet map and nodes - https://hamnetdb.net
• OLSR mesh – http://www.olsr.org/
• Open mesh – http://www.open-mesh.com
• Bad flash recovery – http://www.dd-wrt.com/wiki/index.php/Recover_from_a_Bad_Flash

Step-by-step instruction on patching OpenWRT Backfire 10.03

1. In case of problems compiling OpenWRT on new Debian/Ubuntu distributions it is possible to use debootstrap to install older Debian chroot environment.

   cd ~
   sudo su
   mkdir debian_old
   debootstrap oldstable openwrt_debian
   chroot debian_old
   adduser openwrt
   

2. Install packages required for OpenWRT build system

   apt-get update
   apt-get install git-core build-essential libssl-dev libncurses5-dev unzip gawk zlib1g-dev subversion file python bison gawk sudo vim flex python-m2crypto
   

3. Fetch OpenWRT backfire 10.03 sources and apply patches

   cd
   git clone git://git.openwrt.org/10.03/openwrt.git backfire
   git clone https://github.com/danitool/openwrt-legacy-buildroot-fixes
   git clone git://git.kernel.org/pub/scm/linux/kernel/git/sforshee/wireless-regdb.git
   cp openwrt-legacy-buildroot-fixes/* backfire/
   cd backfire
   ./patch-br.sh
   

4. Update and install feeds for packages and luci

   scripts/feeds update packages
   scripts/feeds update luci
   scripts/feeds install -a -p packages
   scripts/feeds install -a -p luci
   

5. Configure OpenWRT

   make menuconfig
   

   Target System - Broadcom BCM947xx/953xx.

   Target Profile - Broadcom BCM43xx WiFi.

   Select additional packages, such as batman-adv, luci, batmand, olsr and required plugins. Make sure image is smaller than 3 MB, otherwise build some packages as ipk modules by selecting them as [M] and install them later manually.

6. Build OpenWRT

   make
   

7. Modify regdb regulatory database and regenerate regulatory.bin

   cd wireless-regdb
   patch < db.txt.patch
   make
   cp cert.pem ../backfire/build_dir/linux-brcm47xx/crds-1.1.1/pubkeys
   

8. Patch b43 broadcom drivers

   cd backfire
   patch < b43.batch
   

9. Patch wpad-mini

   patch < wpad-mini.patch
   

10. Patch luci

    patch < luci.patch
    

11. Rebuild OpenWRT with changes

    make
    

12. Flash image to router, boot, set password thus enabling ssh

13. Copy/scp updated regulatory.bin to router’s /usr/lib/crda/

14. Reboot

15. Now router can be configured for channel 0