RJ-45 to DB-9 pinout
After getting my X2100 (not to be confused with the X2100 M2) out of storage, I found that I don't have any monitors in the house. We've got an iMac, some Mac laptops, and a couple of HP laptops, but no LCDs or CRTs.
No problem, I thought, I'll just use my handy Dynex USB-to-Serial adapter and fire up a tip session. This was all well and good, except I didn't have any null modem cables.
So I had to make one.
The plan: piece together a null modem cable with my Dynex USB-to-Serial adapter, two female DB-9 to RJ-45 adapters, and an Ethernet cable with a T-568A pinout.
I ordered the DB-9 adapters from BlackBox, but you can get these from just about anywhere.
The hard part was figuring out 1) the order of the cables within the adapters, and 2) what the pinouts should be.
By shining a flashlight through the plastic of the adapter, my best guess at the pin order was:
- Blue
- Orange
- Black
- Red
- Green
- Yellow
- Brown
- Gray
I checked this against some adapters from another vendor; they seemed to be the same. Maybe this order is standard. Anyone know for sure?
After a bit of Googling I found a nullmodem.com page that had my pinout information.
From asking around, I think a tip session only requires the RX, TX, and GND pins. (2, 3, and 5 here.) But since I wasn't sure, I wired up the whole adapter. Note that according to the nullmodem page some pins carry more than one signal. I had to guess when it came to these, but in the end it seems to work.
| Pin | First DB-9 |
Second DB-9 |
| 1 | Black | Brown |
| 2 | Red | Green |
| 3 | Green | Red |
| 4 | Brown | Black |
| 5 | Yellow | Yellow |
| 6 | Orange | Orange |
| 7 | Blue | Gray |
| 8 | Gray |
Blue |
Yahtzee.
