Sunday, 09 June 2013 15:11

Recover bricked TL-MR3020 Wireless N Router

After flashing the latest OpenWRT image file (openwrt-ar71xx-generic-tl-mr3020-v1-squashfs-factory dated 03-Jun-2013), my TL-MR3020 is bricked. All the LED is keep on blinking (about 3 seconds once) except power LED, and the network is getting connected and disconnected every 3 seconds. Very lucky that the problem was fiexed by using serial console and Tftpd32 method.
 
Note:
Using serial console method require to open the case cover (void warranty) from TL-MR3020 router, and solder a10K resistor and 4 ways header pin to it as shown in figure below.
Solder a 10K resistor and 4 ways header pin to PCB
 
 

Prerequisite

  • Tftpd32: A free tftp and dhcp server for windows, freeware tftp server. Very efficient for booting over LAN.
  • PuTTY: SSH and telnet client, free and open-source terminal emulator, serial console and network file transfer application.
  • USB to UART converter support 3.3V

As shown in figure below is my USB-UART converter which come with 6 ways header pin for interfacing. The voltage selector must set to 3.3V since the TL-MR3020 router have its I/O pins working at 3.3V. Plug in the USB-UART converter to computer, I get about 3.6V measure by poking at VCC and GND

USB to UART converter
 
 
 

Opening the case

Pry it open with a thin but very stable blade tool. Start above the mini USB power port where the case is not glued.

Opening case
 
 
 

Connection Diagram

Do not connect the router VCC to USB-UART VCC, it may break your adapter or your router

TL-MR3020 USB-UART
GND GND
RX TXD
TX RXD
USB-UART converter and TL-MR3020 router connection diagram 
 
Finally, connect an ethernet cable from TL-MR3020 network (do not worry about network, it is not working at the moment) to the computer and plug in the USB-UART converter to computer. 
Device manager 
 
 

Setting up network IP address

Assign a static IP address to the computer, it is configured to 192.168.1.2 since the router IP address is 192.168.1.1 (even though it is not working).
Computer IP address
 
 
 

Install OpenWRT from the U-Boot console 

Download the latest Attitude Adjustment RC1 snapshot and save it to C:\Program Files\Tftpd32 (Tftpd32 default installation folder) as shown in figure below
Tftpd32 installation folder
 
Run Tftpd32 as shown in figure below, where Server interface is your computer IP address, it should detected automatically
Tftpd32
 
 
  • Run Putty as show in figure below
  • I'm using COM4 since my USB-UART driver detected as COM4
  • Speed 9600 is not work for me even though USB-UART driver shows 9600, I must use 115200
PuTTY configuration
 
 
Click on Open button, the PuTTY screen should look like this

Using default environment

In: serial
Out: serial
Err: serial
Net: ag7240_enet_initialize...
No valid address in Flash. Using fixed address
No valid address in Flash. Using fixed address
: cfg1 0x5 cfg2 0x7114
eth0: 00:03:7f:09:0b:ad
ag7240_phy_setup
eth0 up
: cfg1 0xf cfg2 0x7214
eth1: 00:03:7f:09:0b:ad
athrs26_reg_init_lan
ATHRS26: resetting s26
ATHRS26: s26 reset done
ag7240_phy_setup
eth1 up
eth0, eth1
Autobooting in 1 seconds

After a 1-2 seconds it shows Autobooting in 1 seconds, when displaying this enter tpl immediately.
 
You will get a U-Boot-console, it shows as hornet>, and you must enter the following commands:
Where setenv ipaddr is the router IP,  setenv serverip is the computer IP, openwrt-ar71xx-generic-tl-mr3020-v1-squashfs-factory.bin is the OpenWRT image file

hornet> setenv ipaddr 192.168.1.1
hornet> setenv serverip 192.168.1.2
hornet> tftpboot 0x80000000 openwrt-ar71xx-generic-tl-mr3020-v1-squashfs-factory.bin
eth1 link down
dup 1 speed 100
Using eth0 device
TFTP from server 192.168.1.2; our IP address is 192.168.1.1
Filename 'openwrt-ar71xx-generic-tl-mr3020-v1-squashfs-factory.bin'.
Load address: 0x80000000
Loading: #################################################################
#################################################################
#################################################################
#################################################################
#################################################################
#################################################################
#################################################################
#################################################################
#################################################################
#################################################################
#################################################################
######################################################
done
Bytes transferred = 3932160 (3c0000 hex)
hornet> erase 0x9f020000 +0x3c0000

First 0x2 last 0x3d sector size 0x10000 61
Erased 60 sectors
hornet> cp.b 0x80000000 0x9f020000 0x3c0000
Copy to Flash... write addr: 9f020000

done
hornet> bootm 9f020000

Note:
It is necessary to unplug the USB-UART everytime a new PuTTY instance started
Read 87290 times Last modified on Sunday, 12 June 2016 10:38

39 comments

  • Comment Link Joyel Thursday, 11 August 2016 18:37 posted by Joyel

    After Recovery i removed the "TTL UART Module Converter Adapter" then connected to my PC, but unable to login... why?...
    After recovery how to setup configuration of WDS Connection with Usage Limitation.....

  • Comment Link admin Thursday, 23 June 2016 16:35 posted by admin

    It should work. Please read here
    https://wiki.openwrt.org/toh/tp-link/tl-mr3420#using_a_serial_line

  • Comment Link Dad Wednesday, 22 June 2016 04:18 posted by Dad

    Mine is 3220 can this procedure works as well?

  • Comment Link admin Saturday, 07 May 2016 18:18 posted by admin

    Did you select the correct speed in the Putty configuration? It is 115200.

  • Comment Link Juan Saturday, 07 May 2016 06:41 posted by Juan

    Hi, I have a mr3020 bricked, because when I tryed to upload the firmware select the wrong archive and I uploaded a zip archive. All the leds are blinking, and when I tried to connect putty with com5 It show illegible ASCII code. I can do anything? or this is a forever bricked mr3020 ? Thank's

  • Comment Link admin Tuesday, 03 May 2016 20:40 posted by admin

    Kootek PL2303 USB to Serial come in two versions, the 5V and 3.3V output version. You should buy the 3.3V output version.

  • Comment Link joyel Tuesday, 03 May 2016 14:12 posted by joyel

    shall i Use "Kootek PL2303 USB to Serial TTL UART Module Converter Adapter" to recover my router
    how to set "Voltage selector" to this product... plz guide me

  • Comment Link admin Saturday, 02 April 2016 23:28 posted by admin

    I may not help you since I don't have the router right now on my hand.
    Anyway did you try tpl instead of TPL?

  • Comment Link Jack Saturday, 02 April 2016 18:48 posted by Jack

    Hi, like Simon when I start putty it constantly shows weird symbols. It seems as if the router keeps booting. I double checked everything but still the same result.

  • Comment Link admin Thursday, 17 March 2016 14:34 posted by admin

    Did you enter lower case tpl?

  • Comment Link Alessandro Thursday, 17 March 2016 10:42 posted by Alessandro

    when run Putty, non stop after a 1-2 seconds.
    Show: "Autobooting in 1 seconds" and run continuously

  • Comment Link chega Tuesday, 23 February 2016 19:16 posted by chega

    try to set in pytty speed 128000.

  • Comment Link Chega Tuesday, 23 February 2016 16:18 posted by Chega

    for some royers need use 128000 speed.

  • Comment Link admin Monday, 22 February 2016 13:11 posted by admin

    2x4.7K=9.4k ohm, it should works. Make sure Tx(router) is connected to Rx(adapter), and Rx(router) is connected to Tx(addapter).

  • Comment Link Simon Monday, 22 February 2016 03:11 posted by Simon

    Hello thx for this tutorial. I try it but on putty there's only any weird symbols. does the resistor must be 10Kohm ? i try with 2 4.7K serialized

  • Comment Link matt Thursday, 21 January 2016 18:30 posted by matt

    great tutorial worked perfectly. recovered a totally bricked mr3020 now working again. thanks.

  • Comment Link Admin Thursday, 29 August 2013 12:45 posted by Admin

    The router supply can get from the USB-Serial adapter. But I would recommended to use external power supply, so do not connect router VCC to USB-Serial VCC.

    Can you ping to your router? How did you bricked the router and what is the symptom.

  • Comment Link hassan Wednesday, 28 August 2013 16:11 posted by hassan

    hi I want to know if we have to supply power to router or without power.
    other is that I have netcomm 3g42w router and its been bricked I have opened it and inside I can read uart on pcb but the pins are not in line they are front and back. is there any way I can upload firmware in it
    thanks

  • Comment Link Marc Rodin Monday, 22 July 2013 02:22 posted by Marc Rodin

    Hey, Thank very much!!!
    Regards from Argentina :D

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