Any help to debrick TP-Link Archer C60 V3 (EU)

Hello! Long story short, I managed to brick my TP-Link Archer C60 V3 (EU), I couldn't fix it using TFTP, and now trying with a serial cable, I actually use Arduino UNO instead of USB UART, when I connect the router with the Arduino and switch on the router, I got a very symbolic line, see below.
Is the Arduino responsible for the problem, and have to use USB UART instead, or the bootloader is broken?

I have no experience with Arduino devices, but a quick websearch suggests that the UNO would be 5V based. Basically all routers require 3.3V (some rather recent and high-end ARM ones might need 1.8V), connecting with 5V to its serial console can show that behaviour and holds a huge risk of permanently damaging the router.

UNO has both 5v and 3,3v port, and I didn't use V pin, I connect it only with Tx to Rx, Rx to Tx and GND to GND if I'm not mistaken

Assuming you used the correct voltage, it might be a baud rate issue.

Hi again,

Thanks for your reply, you are right, the problem was with my Arduino. now that I have purchased a USB UAART device, it works properly, so please help me to fix my problem what should I do to upgrade my Archer c60 v3 firmware.

you have a guide here https://openwrt.org/toh/tp-link/archer_c60_v2

Tp links firmware for the archer c60 v3 has the wrong software version. you can find a corrected version here: Help in unbricking TP-Link Archer C60 V3 - #21 by adrianschmutzler you can install it normally through tftp.