RJ-45 to DB-9

Google RS-232 pin out and you'll find lots of details. Here is the first one I saw:


I know I've seen others but I don't have them handy right now.

You have eight wires in the RJ-45 so you'll have to drop one pin. Losing pin #1 (shield GND) is only mildly risky; if you have a shielded RJ-45 you can run it on the outside.

I suggest monitoring your signals with a break-out box; you can probably get away without routing one of the handshake lines. It all depends upon your application.

OTOH - There are lots of inexpensive RS-232 cables available on the web. Is this project worth saving a few dollars?

Typically, the RS-232 will only use 2 (RX Data), 3 (TX Data), and 5 (Sig GND). If RTS&CTS are required, pins 7&8 are shorted.
On the RJ-45 side, these will corrolate to pins 3,6,and 4 respectively. If you use a RJ-45 to DB9 adaptor, this will be the Black, Yellow, and Red wirs in the adaptor.