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Small linux for routers


Write firmware

mtd write /tmp/openwrt-brcm47xx-squashfs.trx linux
mtd -e firmware write /tmp/openwrt-ar71xx-tl-wr1043ndv1-squashfs-universal.bin firmware

standard config changes

# Disable firewall
/etc/init.d/firewall disable
# Change password
# change banner
vim /etc/banner
# change hostname and timezone
 config 'system'
        option 'hostname' 'openwrt'
        option 'timezone' 'CET-1CEST,M3.5.0,M10.5.0/3'
        option 'zonename' 'Europe/Stockholm'
# Add ssh public key to authorized_keys.
vim /etc/dropbear/authorized_keys
# fix network
vim /etc/config/network
vim /etc/config/wireless

Which version of openwrt is installed.

cat /etc/banner

read /var/log/messages



update package list

opkg update 

install openvpn

opkg install zlib libopensslliblzo openvpn

luci webinterface

opkg update
opkg install luci-admin-full luci-theme-openwrt uhttpd

mount jffs2

mount -t jffs2 /dev/mtdblock3 /jffs/

list wireless

iw phy
  • mac address
cat /sys/class/ieee80211/phy0/macaddress
  • wireless information
iw wlan0 info
  • which clients are connected.
iw dev wlan0 station dump
  • scan for networks
iw dev wlan0 scan

serial cable

chips PL2303 FT232 max3232
standard ftdi

When you have failed to create serial cable buy one that just works.

  • TTL-232R-AJ

TTL-232R-AJ pinout.jpg


recover tp-link wr1043nd

Create a serial cable from a nokia ca-42 datacable.

  • Cut cable of ca-42 and locate the four cables. gnd, rx, tx, ttl

Ca-42 dku-5 pinout.jpg Serial port cummunication values.

115200 8n1

open tp-wr1043nd

  1. Remove the two screws from under the rubber feet at the back of the device.
  2. Unscrew all three retaining nuts on the SMA connectors and carefully push them into the housing.
  3. Push one of the bottom screws back into place to separate the top from the outer frame.
  4. With the top slightly open, push the bottom plastic away from the outer frame.
  5. Remove outer frame.
  6. With a flathead screwdriver or similar tool, gently pry the two front clips apart.
  7. Carefully separate the bottom guide posts from the top of the unit, then pull the top section forward.
  • Connect cables to PCB.


Connect computer and router

Connect cables to wr1043nd and plug usb in computer. Start terminal emulator.

screen /dev/ttyUSB0 115200

Strip firmware

you can use any hexeditor to delete the first 0x20200 byte, it will start with 01 00 00 00 54 50 after delete. Or use dd as in this example.

dd if=wr1043nv1_en_3_9_17_up_boot.bin of=code.bin skip=257 bs=512

put firmware on server

put stripped firmware code.bin in /tftproot/ on tftp server


Flash with working flash

Start router and look at terminal. When waiting for 1 second press

  • when it show autobooting, it will let you get into U-boot.
  • you can set the router ip address by
setenv ipaddr
  • tftpd server address by
setenv serverip

What to write in ubootin

erase 0xbf020000 +7c0000
7c0000: size of the firmware (be aware that u can have diffrent size so u will brick your router) 
tftpboot 0x81000000 code.bin
cp.b 0x81000000 0xbf020000 0x7c0000
bootm 0xbf020000