WR941ND v6 International - behaving in a weird way, maybe bricked?

Installing and Using OpenWrt
1

I got my hands on a TL WR941ND v6 international, the owner doesn´t remember if at some point he installed a openwrt (maybe ddwrt) firmware. In other words, I donno what is running on the router.

The router is in a very weird state:

  • wifi doesn´t work
  • factory reset via button on the back of the router doesn't work
  • power led is steadily on
  • every 60 seconds (or something like that) all the lights turn on for 1s
  • tried to connect via ethernet to all the 4 lan ports and the wan port, the link goes up for a second and then goes down, the same happens every 10 seconds
  • tried to host a tftp with firmware, and boot the router with the reset button on, nothing happens
  • telnet doesn't work, nor http connection

What are my options here?

2

Connect to serial and see what is going on.

https://openwrt.org/toh/tp-link/tl-wr941nd#serial
https://openwrt.org/docs/techref/hardware/port.serial
https://openwrt.org/docs/techref/hardware/port.serial.cables

3

Thank you @tmomas

Just to be 100% sure,
looking at the image of the V6 of the board,
I see the TX,RX and GND. I guess I don't need to connect the +V as well. As long as the ground is shared among the router and the laptop I should be able to read the signal. This also mean that It doesn't matter if I use a 5v or a 3.3v converter.

Is that correct?

4

You must use 3.3 V, this refers to the signaling on the serial line.

5

You are right, the serial protocol use the TX,RX for the high voltage reference (in this case I guess the v6 is the same of the v3, hence the +3.3v)

6

Pretty much universally

  • Never connect V+
  • Always use a 3.3 V converter with a 3.3 V device

Using a 5 V converter will put 5 V on the logic inputs, which can be enough to fry them quicky.

7

Perfect, thanks everyone for confirming.

I wanted to use an arduino mega to read the serial of the router, but the TX pin is at 5.5v so that's a no no. I could use a resistor + diode to step down the voltage, but I guess, given the price, it's safer to go with one of those.