OpenWrt Forum Archive

Topic: Problem with USB-TTL adapter

The content of this topic has been archived between 3 Apr 2018 and 23 Apr 2018. There are no obvious gaps in this topic, but there may still be some posts missing at the end.

elaber wrote:

are you sure you have the correct tx rx pins?


I think so. After a few hours I will upload images of cables. Sorry for waiting

Hi again. Images of my cables :

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This is two level converters (3.3V and 5.0V).
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This is the IC chip MAX3232 for SMD but I used it for TH with this modification wink
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This is the back side and connections (RS232 - MAX3232)

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This is how I use it with my laptop which haven't got serial port and use USB to RS232

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This is MAX232 chip

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This is the connections of MAX232

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This is USB-TTL adapter

http://s12.postimg.org/7j9fkgt19/DSCN5884.jpg

The back side

http://s22.postimg.org/sbb30x1y9/DSCN5885.jpg

The front side

http://s7.postimg.org/86zhujqcr/DSCN5887.jpg

The cable that I use and see sttrange symbols in putty with MAX3232

http://s21.postimg.org/ldg5mel53/DSCN5886.jpg

I bought this cable and want to use it with RS232-TTl adapter but I don't know if it is long ?

This are the schemes of my level converters:
http://sodoityourself.com/max232-serial … converter/
http://www.nslu2-linux.org/wiki/HowTo/AddASerialPort

Thanks for your patience and sorry for slow loading the page.

This is the images in .rar file  http://www.megafileupload.com/en/file/4 … s-rar.html

FOR THIS TP-LINK TL-WR340G I USE MAX3232 BECAUSE THERE IS 3.3V PIN AND USE VCC(3.3V) AND GND AND OF COURSE TX AND RX.

(Last edited by Experimentator on 25 Oct 2014, 22:52)

Any suggestions ?

Experimentator wrote:

Hi again. Images of my cables :
http://s22.postimg.org/sbb30x1y9/DSCN5885.jpg

looking at this image, what wire color is your TX pin?

Green is TX
Orange is RX
Blue is GND.

This cable was from Nokia phone. I cut it and colder at this places this three wires. I identified it according to PL2303HX datasheet and my multimeter beeps (under 50ohms).

Thanks !

looking at the image, green wire is tx. the rest i dont know... big_smile

anway, can you do now an echo test, plug that plxxx module to usb, short tx rx, and send chars from serial terminal like pcomm.

if you can post screenshot of your device manager and your serial terminal, that would be helpful.

OK, here is the picture of settings. I crossed TX and RX but nothing

http://s17.postimg.org/r4003uarj/com_set.png

http://s14.postimg.org/4n3v6254h/com_set2.png

http://s22.postimg.org/miqh7ns1d/screen.png

by "crossed" you mean connect tx and rx pin of the adapter with themselves?

if you can't you see what you type in putty there is something broken in that adapter (or wrong pinout ^^

BTW remember router uses 115200 baud rate..

(Last edited by nebbia88 on 25 Aug 2013, 01:02)

http://s7.postimg.org/iuncldkl7/connection.png

http://s16.postimg.org/vig0hk10x/crosser.png
I use crosser like this to cross tx and RX and nothing

The gray cable should work with your DiY adapter. If you  are sure the circuit for the MAX 3232 is correct, try  connecting TX to RX in it and testing with hyperterminal ( in a computer with a real serial port ) .

As for the Prolific usb cable : there is talk in the forums about the PL drivers not being much cooperative. If you installed original drivers from cable maker, maybe you can try downloading drivers from Prolific site.

rogfanther wrote:

The gray cable should work with your DiY adapter. If you  are sure the circuit for the MAX 3232 is correct, try  connecting TX to RX in it and testing with hyperterminal ( in a computer with a real serial port ) .

As for the Prolific usb cable : there is talk in the forums about the PL drivers not being much cooperative. If you installed original drivers from cable maker, maybe you can try downloading drivers from Prolific site.

DiY adapter works well. When I crossed RX and TX I see characters that I type in terminal. For PL2303HX I use this driver http://www.prolific.com.tw/US/ShowProdu … mp;pcid=41 and nothing is show in terminal.

(Last edited by Experimentator on 3 Sep 2013, 19:05)

Just trying to make sure : your TX and RX wires are connected to pins 1 and 5 of the PL2303 chip ?  Inspect it by sight, or measure resistance again in the points. I believe you are using the continuity/diode test of the multimeter, that usually beeps. Under 50ohm isn´t the same as direct connection . If there is no other component in the way, you should encounter one or two ohms ( approximately the same as when you touch the probes of multimeter to each other ) .

Also, if you can post some clear detailed photos of the adapter board Try taking them in sunlight with some macro setting in the camera / cell phone.

According to datasheet of PL2303HX and with multimeter beeps I found Tx, RX, GND. When I put multimeter's probe to TX of PL2303HX it beeps to TX pin on PCB pinout and the same with GND and RX. I use a magnifier to see solder joints and seems that they are good. Any suggestions ?

EDIT: rogfanther, this days I will not have internet connection so I will not replay you until I connect again. Sorry for this it is ISP problem.

(Last edited by Experimentator on 4 Sep 2013, 23:58)

I still insist : Find the dot that indicates pin 1 of the chip. Is that one of the pins you connected as RX/TX ? Counting from that same pin, find pin 5. Is that the other pin ?

Measure them with the multimeter in ** resistance ** , not continuity ( the beep mode ) .
They should measure about the same as when you touch the multimeter probes together.

That is exactly what I did and I test with beep mode and with resistance I am 100% sure about the identity of pins. So I found dot and according datasheet of PL2303HX I found on chip which pins are TX, RX and GND and with multimeter beeps and resistance found them.  What about test it in linux like BackTrack ? Maybe it is driver problem, I mean Windows driver is bug something.
Please see posts 29,30,31.

Thanks !

I may be sounding harsh, but when I try to help I expect people to follow instructions.  Maybe it is just my way of thinking or lack of patience. Either way, I understand there is a difference in language, and sometimes what we want to say is not transferred correctly to the other person.

I never talked about datasheets, I asked specifically about pins 1 and 5. But if you look and saw that is correct, and you know that your solder is good, my next suggestion is to throw that adapter in the trash and buy a new one. There are others, with pins correctly identified, for under US$ 5 in ebay. Or you can search for a cellphone cable. Search for the models recommended  in the forums. I know for sure the Nokia one works, but have bought one from dx.com and it worked ok also.

Anyway, if you have that MAX3232 cable working , you can use that for working with routers. The USB one is just an addition to the toolbox, but not imprescindible.

I will buy working adapter but I want to repair this one. I am 1000% sure about pins alidentified and connect TX to RX but nothing shows in terminal. Anyway I will but new adapter

Pins 1 and 5 are TX and RX according to datasheet.

(Last edited by Experimentator on 5 Sep 2013, 21:40)

try in another computer. I don´t remember exactly why, but there are some complains about prolific cables in the forums.

I tried in 3 computers with XP and 7 and nothing

Well, then  it would be better to quit wasting time with this one and get another adapter. Maybe you got a faulty one.

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