Hi, my router is working but I want to establish serial connection. I use USB-TTL adapter and here are some lines of serial interface. I've only connect TX of router to RX on adapter and not solder anything, only "touch" router's pin with tester and of course 10Kohms between TX and Ucc which I've soldered on tester.

Here is the output

any suggestions ?

speed:115200

(Last edited by Experimentator on 25 Mar 2014, 18:04)

stupid question: is GND connected?

No, but if I connect it no effect. I did not use router's Ucc

For now I want to have TX working, not to send "tpl" or something

(Last edited by Experimentator on 25 Mar 2014, 18:32)

you need GND and RX, not vcc.

reconnect both router and adapter, it should work.

btw you need a solid connection, touching pads is not good for high freq signals..

So I try to connect TX to RX and GND to GND and nothing

you mean to work properly I must solder wires to pcb ?

Thanks !

i mean that's the proper way that works 100%...

anyway, try also tx to tx (r u sure about adapter pin labeling?) and eventually the usual 10k resistor trick..

http://m.instructables.com/id/How-to-us … the-cable/

When I connect TX to TX there are no symblos in console. I am sure about adapter pin labeling and the resistor according to ohm meter is 9,91ohms so it is 10Kohms.

Thanks for help !

Because I need again help about the same router I will ask here.

Today I solder gold 4-pin connector and 10K resistor.
Settings:
speed: 115200, parity:no, flow control:no

Here is the solder work:

Here is the bootlog:

@=▒r▒r▒BR▒▒▒25 2011 - 12:06:31)

AP99 (ar7241 - Viri▒▒b!▒5▒
sri
▒▒▒▒J▒▒▒ɡ▒9"▒▒▒ init
                    ▒A▒VALUE 1 = 0xf, 2 = 0x10 [0x0: 0x1f]
                                                          32 MB
U▒▒0x100000ff
sect=▒▒▒j
         Flash:  4 MB
▒▒▒0*▒▒H▒▒▒ɡ▒▒1
               Ou▒▒ɥ▒▒5
                       Err:   serial

                                    ▒&▒0
ԁCFG Valu▒                              N▒▒▒▒▒▒addresJ92▒▒͠9 Us▒2▒တ▒addres!▒▒▒▒▒▒▒addresJ92▒▒͠9 Us▒2▒▒▒addres▒
          ▒j
            : cfg▒�▒cf▒▒▒014
▒▒҂▒▒:▒Ҁ▒ad
▒▒
▒CFG Valu▒=<▒j
              : cfg▒�▒cfg▒▒▒214
▒▒҂▒▒:▒Ҁ▒ad
ATHRS26: res▒▒
              ▒▒6 res"=▒
                        eth0, eth1
Auti▒▒▒▒<i
          с9f020000 ...
   Unc▒`J▒▒rrr▒▒*▒▒rr

▒C▒ ▒vf66▒{▒
Prh▒pfF6cC▒FF▒▒C0 byPrhF▒6c
                          6&6cF▒v▒C&ˠF▒▒&+3▒
                                            s`▒&▒sF▒▒▒{ ▒
                                                         sf▒@▒6&▒sPF▒▒6▒▒s`f▒@▒6&▒sF▒▒▒{▒s`f▒@▒6▒s@ach`
PID has                                                                                                ▒C▒▒6`
U200.000 MHz hi▒De@▒&ˠ

Adapter is USB-TTL with CP2104 chip.
I tried to remove the resistor and there is nothing in terminal than tried to add 10K resistor between RX and Ucc and there is bootlog like posted.

Please help me to get working serial connection. Do I need PL2303 chip or I can use CP2104? When I crossed the CP2104's TX nad RX everything is OK but with router there is a problem

THANKS !

put 1k instead 10k, it may help better
Maybe the CP2104 chip is not good for that voltage levels.
I always used converters with PL2303 chip, no single problem

(Last edited by dabyd64 on 2 Nov 2014, 20:26)

Thanks,I am afraid of use 1K because I think that it possible to demage the router somehow. Is it possible ? So you suggest to buy PL2303 data cable ?

Thanks for help !

1K won't damage anything. 100 Ohms, maybe.

With 1K the highest current the pin will take is 5mA. 5 milliAmps!
Usually the limits on these devices are 20-25mA per pin.

If you're afraid of trying, take a PL2303. You could see that the 10K resistor helped a bit. So it's related to the voltage.
There are USB-serial boards on ebay por 1-2$

(Last edited by dabyd64 on 2 Nov 2014, 22:29)

OK, the USB-TTL arrived. It is: http://www.zahranvane.com/image/cache/d … 00x500.jpg

When I connect TX-RX, RX-TX, GND-GND nothing in terminal, not use Ucc pin for the adapter. The speed is 115200. I don't remove 10K resistor. There is nothing in terminal. Then I connect only TX-RX, not gnd, Ucc and and here is what the router boot: ▒▒▒▒▒▒[▒▒▒▒▒▒▒▒▒▒▒▒۶▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ٶ▒▒ö▒▒▒▒▒▒▒▒▒▒▒▒2۶▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒˛▒▒▒▒▒▒▒▒▒ۛ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒؀▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒۶▒▒▒▒▒▒▒▒@▒▒▒▒@▒▒▒▒▒ *▒▒▒▒▒▒[▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒8▒▒▒Ᵹ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ۆ▒▒▒▒B▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ٶ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒[▒▒▒▒▒ض▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ٰ▒▒▒▒▒▒▒▒▒▒▒ ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒@▒▒▒▒C▒▒▒▒▒▒▒▒▒@▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ À▒▒▒▒▒▒▒▒▒▒▒▒H▒▒▒▒▒▒▒▒▒    ▒▒▒H▒▒▒▒▒▒ٶ▒▒▒▒0▒▒▒▒▒▒▒ö▒▒▒▒▒X▒▒▒▒▒▒▒▒▒▒▒Ȁ▒▒▒▒▒▒▒▒▒▒▒▒▒I▒▒▒▒▒▒▒▒▒▒▒▒▒DZ9▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒؆▒▒▒▒▒▒▒X▒▒▒▒▒▒▒▒▒▒▒▒▒▒ö▒▒▒▒▒▒▒@ˆ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒X▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ض▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒oȰ▒▒▒▒▒[▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒;▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ٲ▒▒ ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒0▒▒▒▒▒6▒▒▒▒▒▒▒▒▒[▒▒▒▒▒▒▒▒▒▒▒▒۶▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ٶ▒▒ö▒▒▒▒▒▒▒▒▒▒▒▒2۶▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒˛▒▒▒▒▒▒▒▒▒ۛ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒؀▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒۶▒▒▒▒▒▒▒▒@▒▒▒▒@▒▒▒▒▒ *▒▒▒▒▒▒[▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒8▒▒▒Ᵹ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ۆ▒▒▒▒B▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ٶ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒[▒▒▒▒▒ض▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ٰ▒▒▒▒▒▒▒▒▒▒▒ ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒@▒▒▒▒C▒▒▒▒▒▒▒▒▒@▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ À▒▒▒▒▒▒▒▒▒▒▒▒H▒▒▒▒▒▒▒▒▒    ▒▒▒H▒▒▒▒▒▒ٶ▒▒▒▒0▒▒▒▒▒▒▒ö▒▒▒▒▒X▒▒▒▒▒▒▒▒▒▒▒Ȁ▒▒▒▒▒▒▒▒▒▒▒▒▒I▒▒▒▒▒▒▒▒▒▒▒▒▒DZ9▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒؆▒▒▒▒▒▒▒X▒▒▒▒▒▒▒▒▒▒▒▒▒▒ö▒▒▒▒▒▒▒@ˆ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒X▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ض▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒oȰ▒▒▒▒▒[▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒;▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ٲ▒▒ ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒0▒▒▒▒▒6▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒@▒▒▒▒▒▒▒▒▒▒▒▒▒@

After all I removed 10K resistor and again connect TX-RX, GND-GND, not ucc pin used and there is nothing in terminal. Then connect TX-RX and nothing in terminal(with 10K there was what I post ▒). What to do next ? Thanks for your time !

EDIT: here is the same adapter: http://www.aliexpress.com/item/pl2303-m … 46796.html

(Last edited by Experimentator on 4 Nov 2014, 18:17)

I used that adapter hundreds of times, it works well.
Never disconnect the ground . Nothing good can happen. I rare cases it may damage the serial converter

That behaviour is very strange. Post photos of the board itself, maybe there's something else.
Often, they put resistors on the serial lines and causes problems.

(Last edited by dabyd64 on 4 Nov 2014, 22:47)

Here is the front side of router's PCB.

That resistors are suspicious.
Can you clean that yellow thing to allow seeing what's under it?
And  what is Vcc, Rx Tx, Gnd?

There is nothing under it

But the tracks are not clearly visible because of it.

Try to bypass C496 , it works for me.

https://forum.openwrt.org/viewtopic.php?id=42234

(Last edited by xopal on 4 Dec 2014, 02:33)

did you try any other baudrate? try lowering to 57600.

Why are those resistors needed anyway? Just connect the serial to the opposite pins (TX->RX, RX->TX) and don't forget the ground.

OK, I bypassed the capacitor and crossed the pins where was the capacitor. When I check with multimeter about continuity and there is between TX pin and the other side on solder crossed (not to the CPU) but now there is nothing in terminal. Don't add 10K resistor. Tried with PL2303Hx and CP2104.

Any suggestions ?
Thanks and sorry for wait I was busy

(Last edited by Experimentator on 9 Dec 2014, 17:28)

All resistors are soldered, I use a magnifier to see near the yellow

Ideally, look at the signal with an oscilloscope.  The transmit signal should idle at 3.3 volts and pulse to ground with data bits having good fast transistions.  If you only have a voltmeter you can still check that there is 3.3 volts on the TX pin out of the router when nothing is being sent.  Like the others said, always connect the ground.  Confirm with an ohmmeter that the pin you are calling ground is indeed grounded (zero ohms to internal grounds like the antenna coax braid, USB socket shell, etc.) Use a good power cube to power the router so there is no ground loop between the router and PC.

(Last edited by mk24 on 9 Dec 2014, 17:34)

GND - TX is 3.3V
Everything seems to be good but there is no serial output. I don't have osciloscope

(Last edited by Experimentator on 9 Dec 2014, 18:27)