Topic: Debricking TP-Link TL-MR3040 3G Router

I bricked my MR3040 last evening also. Unfortunately, I have already written to tp-link tech support telling them that I had tried installing a custom firmware and they advised me to press the reset button, which I had done without any results and she said that beyond that, they may not be able to assist further.

I'm trying to figure out how to flash the latest stock firmware back onto the device using the U-Boot technique. When I turn the router on, all I see is the power LED on and nothing more. There is no signal on the Ethernet port. How do I connect the modem to my laptop which does not have a serial port? Do I connect the modem's power/micro USB port to a USB port on my laptop (no device gets detected when I do that) or do I use the USB port on the modem and a USB port on my laptop? I have two USB-male Serial RS-232 cables and a female-female converter that can allow me to have a USB to Serial to USB cable (using this technique didn't show anything on putty either sad ). Somebody please help...

2 (edited by hnyman 2013-01-04 13:14:37)

Re: Debricking TP-Link TL-MR3040 3G Router

You can't use the router's USB port. It is no "serial port" in that sense. So, "USB to Serial to USB" will not work.

You need to connect into the serial header in the router's circuitboard (and then the other end can be a USB-serial converter at your PC).

Read the wiki: http://wiki.openwrt.org/toh/tp-link/tl-mr3040
The serial is p1 layout: p1 |VCC|GND|RX|TX|    (<-- meaning the order of serial pins from p1 text)
And look to the P1 header in the right top corner. It has four dots, into which you need to connect your serial adapter.
http://wiki.openwrt.org/_media/toh/tp-link/tl-mr3040-v11_small.jpg

You need something that creates a low-power "TTL" serial port into your PC, possibly using a serial-USB converter.

When I had to debug my router in November, I bought a cheap serial converter from Ebay. Look for something like that.
http://www.ebay.co.uk/itm/290526138405
http://www.ebay.co.uk/itm/270805125757

3 (edited by Saichovsky 2013-01-04 13:38:52)

Re: Debricking TP-Link TL-MR3040 3G Router

I have a miniUSB cable with the miniUSB connector end cut off, so I just have wires sticking out. I can work with that, can't I?

Plus I should've mentioned that I am not an electronics person, just flashing firmware bin files and enjoying surfin the web... smile

4 (edited by hnyman 2013-01-04 13:45:00)

Re: Debricking TP-Link TL-MR3040 3G Router

Saichovsky wrote:

I have a miniUSB cable with the miniUSB connector end cut off, so I just have wires sticking out. I can work with that, can't I?

No. USB signalling is not normal normal old-school serial port signalling, as far as I know.

You don't need any special electronics skills, but you need a suitable serial port, serial cable, and then you just connect the pins correctly to the opened router's circuitboard.

You might use USB-converter to create a proper serial port to your PC, but otherwise forget about USB/mini-USB. You are looking for old-school serial port connections ;-)

5 (edited by Saichovsky 2013-01-04 13:55:47)

Re: Debricking TP-Link TL-MR3040 3G Router

OK. And old school serial port conections are like the Nokia cable? I've read somewhere that the miniUSB gives 5V, but what we need is 3.3V, right?

And what's the difference between a normal USB cable and a USB TTL cable, how does one tell them apart?

Re: Debricking TP-Link TL-MR3040 3G Router

Saichovsky wrote:

OK. And old school serial port conections are like the Nokia cable? I've read somewhere that the miniUSB gives 5V, but what we need is 3.3V, right?

And what's the difference between a normal USB cable and a USB TTL cable, how does one tell them apart?

How did you revert back to talking about "USB cables"? There is no "USB TTL cable" as itself. There are USB-serial converters (like those two I gave links to) that convert USB port easily to a TTL-level serial port, so that you can then connect the router with a serial cable (usually just 4 separate wires). But "USB" is used there just for connecting the converter to your PC. Talking about USB cables leads you into astray. (Some of the converters are marketed as USB-to-TTL, but it is just a USB-serial converter + serial cable).

As ar as I know, you need a 3.3V serial port.

An ancient "Nokia cable" is one such converter. But the key thing there is the built-in USB-serial conversion and then a normal serial cable from the converter to the phone (or router in this case). Much easier is to buy a small made-for-this converter.

Re: Debricking TP-Link TL-MR3040 3G Router

USB is to TTL serial what English is to Russian. DO NOT just poke random wires in!
Do as hnyman suggests, and get a proper cable/converter eg from the ebay links provided. Fiddling about with stuff randomly may well, in this case, break your router permanently.

Re: Debricking TP-Link TL-MR3040 3G Router

Thanks guys. I think I've understood. I got me a CA-42 this evening. Will update on debricking progress tomorrow. Thanks again for the advice

Re: Debricking TP-Link TL-MR3040 3G Router

Saichovsky wrote:

Thanks guys. I think I've understood. I got me a CA-42 this evening. Will update on debricking progress tomorrow. Thanks again for the advice

Hi,
any updates?

Re: Debricking TP-Link TL-MR3040 3G Router

Hi doiga.

Been out of my home country since posting that. Debricking still pending; will share an update as soon as I manage to do something on the modem.

Re: Debricking TP-Link TL-MR3040 3G Router

Saichovsky wrote:

Hi doiga.

Been out of my home country since posting that. Debricking still pending; will share an update as soon as I manage to do something on the modem.

Ok, I will wait for news!

12 (edited by Saichovsky 2013-06-18 08:40:23)

Re: Debricking TP-Link TL-MR3040 3G Router

Hi people,

Sorry for the long silence, been mighty busy of late. I think I am now ready to start the debricking. I got a USB-TTL cable with contact points with unfamiliar labels and that is where I am currently stuck - not knowing which way to go. Here's a pic of my USB connector. http://s11.postimg.org/kpexmi0k3/USB_TTL.jpg

What's the meaning of all these DSR, RI... or rather, what goes where into the motherboard for my bricked MR3040?

Thanks!

S.

13 (edited by Boompje123 2013-06-18 10:03:21)

Re: Debricking TP-Link TL-MR3040 3G Router

Is this a CA-42 with 5 cables coming out?
What colors are the cables? (picture is kinda dark, just wanna make sure)

Take a look at hnyman's post above
In the picture in the top right corner you see "p1" with 4 holes next to it. The order is (from p1 - so upside down on the picture): VCC|GND|RX|TX

You need to figure out which of the five cables are GROUND, RX and TX and connect those three (use google - black is usually ground, the others I don't know - I don't own this cable nor own this router). The RX cable should go in the TX hole, the TX cable should go in the RX hole. GRD connects to GRD

You do not need to connect anything to VCC

Download putty
Click the "serial" option in the left colomn
Set it to the right settings:
Bits per second (speed): 115200
Data bits: 8
Stop bits: 1
Parity: None
Flow control: None

Let Putty listen on the right COM port (the one where your USB is connected - you can check that in the "device manager" of Windows)

There are some more instructions on the wiki, but at this point the wiki doesn't say what commands to use once you have established a serial connection.
http://wiki.openwrt.org/toh/tp-link/tl-mr3040#serial.console

I can't help you any further, but start by successfully setting up a serial connection and entering the router that way. Once you're in (after you've typed "tpl" as the wiki says) come back and I'm sure people will try to help you with what's next smile

Hope this helps with the first steps!

14 (edited by Boompje123 2013-06-18 10:01:29)

Re: Debricking TP-Link TL-MR3040 3G Router

I was wrong. the Wiki does have the instructions for debricking once you're in uboot (serial):

http://wiki.openwrt.org/toh/tp-link/tl-mr3040#manual.flash.under.u-boot.serial.console

You will need a tftp server running on a computer which has a firmware file
The ip of that server needs to be 192.168.0.100 (I think)
Assuming you are on Windows, I always use this one:
http://tftpd32.jounin.net/

Connect the computer to the LAN port of the router

Then in Putty (the Wiki uses screen, I prefer putty) - which has a connection using serial (so after typing "tpl"):

type: tftpboot 0x81000000 openwrt-ar71xx-generic-tl-mr3040-v1-squashfs-factory.bin
to transfer the firmware

type: erase 0x9f020000 +0x3c0000
to erase the old firmware

type: cp.b 0x81000000 0x9f020000 0x3c0000
to flash new firmware

type: bootm 9f020000
to reboot

15 (edited by Saichovsky 2013-06-18 13:31:26)

Re: Debricking TP-Link TL-MR3040 3G Router

Hi Boompje123,

Thanks for your help. What I am unable to figure out is this:

The wiki mentions VCC, GND, RX & TX, but my TTL has RTS, RI, DSR, VCC and DCD (or VCD?). My challenge is knowing what on my USB-TTL is RX, TX etc., since they've been labelled otherwise.

The packaging said it was a C-42 and the cable does open a COM port when plugged in. I remember the cable had 4 wires when I bought it, but I soldered on a fifth wire just to cover all contact points.

16 (edited by Boompje123 2013-06-18 13:49:12)

Re: Debricking TP-Link TL-MR3040 3G Router

The labels on wires never say "rx" "tx" as far as I know, its always a matter of figuring out which is which I think

What I don't understand is that you soldered in a fifth cable? Where did you read that thats necessary?

The CA-42 (also known as DKU-5) works like this for serial connections:
1) you buy it
2) you cut of the end
3) you find 3, 4 or 5 wires, all i different colors
4) you find out which wire is which (google)

and then you hook it up.

Again: which colors are the wires that were originally attached to the cable? that's your starting point

Re: Debricking TP-Link TL-MR3040 3G Router

I think what I got was an imitation of the CA-42 because the colours didn't match. I don't really remember why I soldered all the points, maybe because the colours didn't match what's on the web and I didn't want to leave anything to chance.

18 (edited by Boompje123 2013-06-18 18:44:13)

Re: Debricking TP-Link TL-MR3040 3G Router

Sorry I can't help you with this one

Good luck.. once you do figure this out, you're good to go wink
and then debricking won't be that hard

Re: Debricking TP-Link TL-MR3040 3G Router

pic of the other side of adapter?

Re: Debricking TP-Link TL-MR3040 3G Router

Other side pic:
http://s8.postimg.org/svh44abhx/USB_TTL2.jpg

Re: Debricking TP-Link TL-MR3040 3G Router

well.. is that my imagination or blue is labeled TXD, green RXD, white GND?

Re: Debricking TP-Link TL-MR3040 3G Router

Haha... also noticed it after pasting the image here. Never thought of checking other side. Trying to debrick now smile

Re: Debricking TP-Link TL-MR3040 3G Router

Sweet! Let us know how it went

Re: Debricking TP-Link TL-MR3040 3G Router

Success :-)

I bricked it while trying to install OpenWRT.... Now that I have the right tools to debrick, I guess I should continue from where I left off, no? smile

Thanks everyone for your help, and for persevering thru taking this n00b through this stuff...

Saichovsky

Re: Debricking TP-Link TL-MR3040 3G Router

Oh man i was really enjoying reading all this. Can you post outcomes?