Hello. Recently I installed Openwrt on my Archer C20 V5 EU. Sadly I uploaded sysupgrade file to Openwrt Firmware Upgrade. Afterwards It started to blink once and stuck at bootloop. Then I pressed a RESET button and then it blinks all light twice, bootlooping. I Bought a CH341A Programmer and Rpi Pico since TFTP method don't work. The wired connection is dropping. Any advice welcomed.
post the serial console output while running the TFTP flash attempt.
I cannot connect to it using tftp. When I set up wired connection it drops after half a second.
not what you were asked to post ...
I asked If I could or how to fix bootloop since tftp don't work
I can read, and it doesn't work for you.
If you ask for help, how about you just do what you're asked, instead of questioning the help you're about to receive ?
Are you sure that TFTP recovery does not start? Hold down the reset button while you plug the power in, and keep holding the button. After some time (20-30 seconds) the WPS light should come on indicating that recovery mode is active.
Note that you need a specially prepared firmware for TFTP recovery, or the bootloader will get clobbered and then the device is a hard brick which will require hardware writing directly to flash to resolve.
To interact with the bootloader by serial, which is the most certain way to handle most bricked situations, you will need a USB to serial adapter such as a CP2102. I know that technically the CH341 has an async mode but I could never get it to work.
About the WPS light. I tested and its working for about 12 seconds(enough for flashing I guess).
About file. I have tf_recovery.bin file by Linaro985. There is guide online. Here is link: https://superuser.com/questions/1776296/how-to-recover-bricked-archer-c20
I guess I will use this file since it's recovery for openwrt router and not tp-link original. I'm trying to start a tftp on linux. Sadly no derect guide online as I found.
There's a TFTPd built in to dnsmasq, guides for setting it up should be available online.
If you don't want to configure it in your Linux, boot Openwrt off a flash drive, and set it up there.
Yes very simple to set up if you have an extra OpenWrt router.
Change the LAN IP to 192.168.1.66 which is what TP-Link expects to download from. (The TP-Link will be 192.168.1.88, so you would keep LAN as a /24 network.)
In the first block of /etc/config/dhcp (config dnsmasq), add these two lines:
option enable_tftp '1'
option tftp_root `/tmp/tftp`
Then restart dnsmasq (service dnsmasq restart) which will create an empty directory /tmp/tftp, then scp the firmware file to /tmp/tftp. /tmp is a RAM disk with a capacity of half the router's RAM size, so it will have space for a larger file than can be stored in 8 or 16 MB flash. Files in /tmp get erased whenever the router is rebooted.
Edited to correct IP address.
you need to flash by connecting via switch
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There is detaliled guide with same problem. If someone have it, here is link :https://morty.ononoki.org/?mortyurl=https%3A%2F%2Fwww2.rigacci.org%2Fwiki%2Fdoku.php%2Fdoc%2Fappunti%2Fhardware%2Ftl-ac750_archer_c20v5
hope it helps.
So what, it's solved ...? How ?
I'm currently following it.
so you're doing the TFTP recovery you said (multiple times) wasn't working ?
interesting ...
You're asked to provide the output from the serial console. You have the "CH341A Programmer", right? You have connected it to the router, right? And you have a terminal (console) showing what's happening as you do the TFTP recovery, right? I'd provide that console text to @frollic instead of asking others to follow some detailed guide. We don't have a broken Archer C20 
I suggest using the instructions on the OpenWrt C20v5 wiki page to create your own recovery file rather than trust someone else's. When you download the stock firmware to extract the bootloader image, be sure to get it from the TP-Link site for the country / region marked on the router's nameplate label, and the country code in the file name matches.
Update to the story. I started atftpd service in terminal and placed Linaro985 tp_recovery.bin file in /srv/tftp. After I connected. tiped $ tftp 192.168.0.66 .The router power light started to blink rapidly. About a minute and the blinking lights gone. Only power light and the connected to computer light are visible and turned on. I tried entering 192.168.1.1 but I can't enter the openwrt admin page. Also disabled https in all windows, but, no connection page popps off.
if you can't see the image being pulled via TFTP, by the router, don't bother.
we have no idea what "Linaro985 tp_recovery.bin" contains, and what the default config is (might be stated in the blog though).
nor would the router try to pull "linaro985 tp_recovery.bin" by default.
I assume you disabled the firewall before attempting the TFTP recovery ?
I also assume you tried putting a switch between the router and the TFTP host ?
Have you already tried serial ?
Update Update. Everytime I turn router on. All lights are blinking twise as was before but only once (all lights blink 2 times). Then only power light blinks rapidly and stays powered on.