Topic: 5 wired dku 5 cable

Hi all,
after playing around with my tplink router and successfully bricking it tongue i try to unbrick it now via the serial console. it's possible but i can't identify the wires of the dku 5 cable.
as i could find on google and on the forums there are many dku cables around, each of them different in colour code and number of wires.

mine has 5 wires: white, blue, black, red and yellow.

i'm thankful for every reply, best regards!

Re: 5 wired dku 5 cable

OpenWrt / reset button doesn't work on backfire!!
Use a Nokia Serial Cable on an ARM9 Linkstation - NAS-Central Buffalo - The Linkstation Wiki
File:CA-42 DKU-5 pinout.jpg - NAS-Central Buffalo - The Linkstation Wiki

Re: 5 wired dku 5 cable

thanks smile

red = RX
blue = TX
black = GND, but not sure yet

i loosely assembled the wires on the board but the serial monitor just shows any random digits, nothing what makes sense. how can is solve this problem or is the router hopelessly bricked?

Re: 5 wired dku 5 cable

connect the red and blue wire directly (no connection to router) and type something in your terminal program. if you receive what you typed in, you should have found the right wires (assuming that you have turned off local echo).
have you set the connection settings right?

5 (edited by cornelus2009 2012-02-24 21:09:35)

Re: 5 wired dku 5 cable

if u have nonsense caracters, means u selected wrong transfer rate

put 115200, and u are done.

Burlacu Cornel

Re: 5 wired dku 5 cable

thank you guys!

no need of any resistor between RX and TX? No GND, +3,3V connection to the router? what serial monitor is recommend under windows? atm i'm running putty and terateam but i don't get any output when i connect RX abd TX! entering text in the console is also not possible.
usually, i'm under linux but the cable is not supported by the kernel / no modules are available.

Re: 5 wired dku 5 cable

Which router?

Re: 5 wired dku 5 cable

fyi wrote:

Which router?


Re: 5 wired dku 5 cable

TP-Link TL-WR741ND - OpenWrt Wiki - Serial


Re: 5 wired dku 5 cable

a resistor is probably a good idea, just in case you end up connecting tx to +3,3V or GND. If you don't receive what you type in (no local echo of the terminal program), then you probably have the wrong wire picked.

11 (edited by wrtcat 2012-03-06 17:48:41)

Re: 5 wired dku 5 cable

I got a genuine nokia dku-5 cable which have the same cable color code as yours. Since I don't have a multimeter I tried your suggestion and connected blue and red as well as the black cable as mentioned.

I started the terminal and got scrambled characters displayed like you. At first i thought that there is a problem with the baud rate but even trying any baud rate available could not solve this issue. Depending on the baud rate there is scrambled or no display at all.

Following this, I think your color combination could be either wrong or different. I don't know. The strange thing is that after reversing the blue and red cable i still got scrambled output. If blue and red is really a working Rx & Tx then this should not happen.

I was careless enough to cut the cable in such a way which made it impossible to reconnect the pin plug to the usb converter in order to access the right connection through the original pin plug hmm I also destroyed the pin plug during the attempt to open the plug in order to see to which pin the colors are leading. In fact it is impossible to access the inside of the pin plug because every thing is infused in some kind of resin.

Rx & Tx detection through loopback failed as well. There is no combination which loops the signal back.

Maybe the converter needs 3,3 V power supply in order to working properly but the question is still the same... where? Even if the red/blue combination is right and black is ground then there is still a white and a yellow cable.

I spend hours searching for color code informations on the specific genuine dku-5 but everybody seems to connect with the cloned ones.


Re: 5 wired dku 5 cable

you could open the usb-side connector of your cable to access its pcb. maybe the manufacturer was kind enough to print something useful on the pcb.
found on that website: … rial-port/

13 (edited by wrtcat 2012-03-06 21:55:04)

Re: 5 wired dku 5 cable

Indeed it needs 3,3 V in order to work properly. Loopback and serial communication with the router works perfect now. Here comes the color code for the genuine Nokia DKU-5:

Yellow: Irrelevant
Red: 3,3 Volt
Blue: Rx
White: Tx
Black: Ground

MBS wrote:

you could open the usb-side connector of your cable to access its pcb. maybe the manufacturer was kind enough to print something useful on the pcb.

Yes you are right, but in this case I'm pretty sure that the converter in the USB Plug is infused too.