How to flash openwrt and dd-wrt to locked wifi router TP-Link TL-WR841N V9

TPLink jumped the gun on the FCC decision regarding firmware lockouts
They made re-flashing the devices with OpenWRT or DD-WRT through the webUI next to impossible
However with a serial connection to the router, we can figure out how to flash whatever we want. You can also use this serial console + tftp method to debrick or unbrick your TP-LINK WR841 in case you bricked it.
First, let's see what we have here
TP-Link WR841N V9
Now I will come to TP-LINK site and get another flash version
Now we can download the firmware
And now let me flash even the original flash from TP-LINK and see what happen
"Error code: 18005 Upgrade unsuccessfully because the version of the upgraded file was incorrect. Please check the file name."
So I could not flash even the original flash from TP-LINK neither DD-WRT nor OpenWrt
However I will download firmware from both OpenWrt and DD-WRT and play around with them
To do this way, you need to solder the serial port to your router. You can find the guide from the Internet or see my video guide how I do it.
Most importance is find TX - RX and GND and connect them to your USB to TTL module
And you can order this module with about $2 from ebay or Aliexpress
After connect your module to router serial interface, you can use Hyper Terminal or Putty console to connect to your router
But before doing that, you have to check and setup the COM port assigned to your module
Set serial port speed to 115200, Data bit 8, Parity None, Stop bit 1, Flow control None
Now we can connect to the router
Set all parameter the same to what you had set for your COM port.
Now you are connected to the router's serial interface. During 1st second enter "tpl" to interupt the booting sequence
Now we will prepare tftp server and the firmware to flash my locked router
Now set your computer's IP address to 192.168.1.100
Run tftp program and choose server interface to the IP you have just set. Uboot needs the tftp server to be listening on port 69
Then set current directory to place when you put your firmware in. You can click showdir to check these files
Now come back to the router, you can check some parameter in U-boot
Now set router and tftp server's IP address with following command
setenv ipaddr 192.168.1.111
setenv serverip 192.168.1.100
then printenv
Now we can load the firmware over TFTP with "tftpboot 0x80000000 [and the file name that you put in tftp server]
type "printenv bootcmd" and take note of the address and use it as flash erase start address
now type "erase 0x9f020000 +0x3c0000" note is the number you got from "printenv bootcmd" maybe you can have difference number
Now we will copy RAM content to flash: "cp.b 0x80000000 0x9f020000 0x3c0000"
Now we will setup the boot: " bootm 0x9f020000"
Done, it seem that my router is now booting with OpenWrt firmware
I can access luci interface via brower now.
You can use this serial tftp method to debrick / unbrick your bricked routers
One step further we will flash the router with another firmware DD-WRT
Now it is easy as you can directly do it from luci interface. I believe it is easier flashing DD-WRT from OpenWrt but not the other way
Just brouse DD-WRT router database and find LT-WR841ND ver9 firmware
It is easy to flash it from luci
Now your router is running DD-WRT firmware

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