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RS232 to RJ45 Pinout

Posted on 2004-11-08
Medium Priority
Last Modified: 2011-10-03
Hello all,

I have an RS232 connector as follows:

3 > TD
5 > RD
7 > RTS
9 > CTS
11 > DSR
12 > RCVRDY -
13 > SIG GND
14 > DTR
19 > RESET -

Now, I need to connect this to an RJ45 connector. I need pin 3 as Transmit and 5 as Receive from the RS232 to connect to the RJ45 so I can connect it to my sniffer to capture data.

What pins do these connect to on the RJ45 connector?
Question by:jayrod
LVL 69

Accepted Solution

Callandor earned 1000 total points
ID: 12527397

Author Comment

ID: 12532301
Callandor, thanks for the info, interesting page.

But I guess what I need is a better understanding of what to connect the transmit and recieve pins on the RS232 connector to the RJ45.

I know on the RJ45, 1,2,3,6 are transmit and recieve, but since I can only pin to one pair, which do I use on the RJ45...1 and 3 or 2 and 6 etc.

Expert Comment

ID: 12771175
Here is an example from the connecttech site mentioned above.  I would only add that I would buy a rj45 to db25 kit and build it to fit the sniffer spec.  Keep in mind that on the RJ side pins 1/2, 3/6, 4/5 and 7/8 are paired.  It is also a good idea to use pairs to carry the RX and TX signals.

CB004 Pinout

RJ 45 Jack <-> DB25F

CTS 9  <-> 4 RTS

DTR 7 <-> 8 DCD

GND 6 <-> 7 GND

TX  5 <-> 3 RX

RX 4 <-> 2 TX

DCD 3 <-> 20 DTR

RTS 1 <-> 5 CTS

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