The Easy way out : Easy flashing without opening router!!

If u thing You can live with 4 mb flash/32 Mb ram, Or just want a stable router that do not hang or reboot unexpectedly, you can try Factory firmware recovery method.  In this method You do not have to even open up your router.  No need TTL adapter and as such.

But Be warned, with small flash and/or 32 Mb memory It's not possible to use the router other then for routing securely.

OK, here is the easy way....

If you have a tp-link router and it's 8xx series or 7xx series i.e. tl-wr840/841n or tl-wr-740/741 or tiny routers with USB port you can use factory recovery to install custom firmware such as openwrt or dd-wrt!!

Most people use windows, so I will go with windows installation steps here.

First download firmware from openwrt download page, use the latest version for your router.,
https://downloads.openwrt.org/
For DD-wrt go to their download page and search in beta folder here,
https://dd-wrt.com/support/other-downloads/
OR for actual recovery go to tp-link website to download firmware for your router..search for your router and if found go to download page for that router,
https://www.tp-link.com/en/

first of all, you need to set up a TFTP Server on your computer with IP 192.168.0.66/24. i.e. your computer address at 192.168.0.66, netmask 255.255.255.0 gateway to any address in subnet 192.168.0.x i.e. 192.168.0.86(your routers address!!, not important at this time). Please note that you are actually setting up your computer with tftpd server at static ip address of 192.168.0.66(Very Very Important).

Download tftpd32/64 (in same package) from below link and install in your windows. Setup a directory for your router to download your firmware file that you have downloaded from above sources of openwrt/dd-wrt or tplink website.
https://bitbucket.org/phjounin/tftpd64 or,
http://www.tftpd64.com/

1. Here comes the most important part,switch off your router and Connect a LAN port of your router to your TFTP Server machine(your computer).
2. Hold down the Reset button on the back of the router and switch it on till you could see the information below in the log viewer option.
3. Obviously, you have to press the log viewer at first, you can see the name was(requested by your router to your computers tftp server) :: routername_tp_recovery.bin. i.e. if it's tp-link tl-wr841n/nd ver 2 then file name should be wr841nv2_tp_recovery.bin.  Here are some more names your routers bootloader may request if it's different version of tplink 841 or other router,
wr841nv8_tp_recovery.bin (for v8.x); for v9 wr841nv9_tp_recovery.bin; for v10 wr841nv10_tp_recovery.bin; for v11 and v12 wr841nv11_tp_recovery.bin. Note: You can find the version number of your router, on the back sticker of the router.
4. You may need to try step 3 several times.

5. Rename the file you have downloaded from above openwrt or dd-wrt or tp-link suitable for your router to the name your router is requesting for download i.e. to flash the image to your router via the bootloader, It's actually bootloader u-boot requesting for the firmware image(binary) file. So, rename according to what has been requested by the routers bootloader..if it's tp-link tl-wr841n version 9.x then it should be renamed to wr841nv9_tp_recovery.bin. Other tp-link routers such as wdr4300 ver 1.0 file should be wdr4300v1_tp_recovery.bin.  For tplink tl-wr841hp ver3 it should be, wr841hpv3_tp_recovery.bin.  Now copy that renamed file to your tftp server download directory that you have set while setting up tftpd32/64. Also Browse to the download folder ensuring the download path and file name is correct.

6. Now Switch off your router.  Then hold down the reset button on the back of the router, while reset button keep pressed now switch on your router. After turning on the router keep it pressed until you see your router is requesting recovery file in the tfpd server log viewer window!! and a popup messag appears like below image,

7. Now wait for some time until router reboot itself, You will see router lights turning off and on again. If the flashing is successful you will be able to login to web interface of your router with your new firmware or recovered firmware. Pls. remember,  if openwrt or tp-link or dd-wrt installed, router will restart at address 192.168.1.1 or 192.168.0.1, will also try assigning your computer a DHCP address, so after reboot, do not forget to change to "automatic ip or DHCP" mode in windows instead of set static ip.

Important Notes/Notice:
1. Your routers bootloader may not support this tftpd recovery mode.  To make sure, you should try this method for some time, at least 10/15 times, giving 5 to 8 minutes time for each trial.
2. Some routers tftpd address may be different., i.e. Some tp-link router(u-boot bootloader) expects tftpd server at 192.168.1.66/24 which is a different subnet, so should configure your computer accordingly. So, In this case, Your computers ip should be 192.168.1.66, netmask 255.255.255.0 gateway 192.168.1.86 etc.
3. If the router's IP (192.168.1.1) doesn't respond to ping(after reboot), try clear ARP cache on your machine/computer, run in command prompt,
arp -d
4. After reboot if you have installed openwrt, login is, Login id: admin, password: none/empty.  If it's dd-wrt login is: root or admin, password is admin, for tp-link it's id/pass, admin/admin

Warning: If your router firmware image name got boot in it(that you have downloaded from tp-link website for your router), meaning it got bootloader appended at the beginning of the firmware. In such cases if it's successfully flashed, your router may be bricked completely.  Even serial console will not help in this case.  U will need J-tag or external programmer to reload bootloader with firmware into your flash chip!!!  If you wish to get a stripped of Bootloader firmware image i.e. firmware image/bin file without bootloader you can try downloading it from this website,

http://www.friedzombie.com/tplink-stripped-firmware/

But if you are using linux/unix variant i.e. freebsd, then it's a different ball game, u can easily strip the firmware of off it's bootloader with dd,
you will need to strip out the first 0x20200 bytes (131584 bytes),
dd if=orig.bin of=tplink.bin skip=257 bs=512 (dd is a linux command line tool)

But after flashed, if router not booting but light up(router leds) and system or power light flashes rapidly or any other led light flashes, that means not everything is lost.  You still got a functioning boot loader signalling you that you have flashed the wrong firmware.  In such case if you try going into 192.168.1.1 or 192.168.0.1  You may find web interface of your bootloader(Emergency web enabled) and you can flash another firmware carefully selected for your router by you!!.  Even if you do not get the web interface, no worries, you can still flash another firmware image/bin file with TFTPd method, explained in detail above.

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My Profession : By trade I'm a Software Engineer.  But I Love trading currency or Forex markets and trade mostly eurusd markets.  So I needed a reliable and dependable router system that I think openwrt or tomato can provide with a good ISP.  I trade with reputable International Forex brokers.

To know how to do Forex Trading go here : Forex Trading: My regular source of income

For signals on eurusd go here My Forex Trading Journal