Re: Custom CAT-5 / DB-9 serial cables

I got this to work the other day. The colors don't matter as long as you are careful to use the same color for the same pin number on each end of the cable (i.e., if red is pin 1 at one end, it should be pin 1 at the other). You will have 8 wires in the adapter to plug into nine pins, so you need to leave one pin blank. I can't remember which is OK to leave blank but it was easy to figure out from Colby's help file. Note: Despite what the documentation says, if you're really using eight wires straight through you do not need to short three wires on the PC side. Carrying those three leads all the way through the CAT5 cable to the Slink-e solves the problem, and it's easier than stripping and soldering wires inside that little plastic shell.

The trickiest thing about this whole strategy is that it's easy to get the pins mixed up, especially if you just look at the housing and assume that the left-most pin on the top row is pin 1. In fact, the male housing and the female housing are sort of mirror images of each other; the pin numbers are fairly scrambled. Pin 1 may be top left on the first adapter, but not on the second even when you are looking at them from the same angle. To make it easier, the adapters always include tiny, tiny, tiny numbers next to each pin slot, but everything is so close together that it's still tricky to puzzle out. I used a magnifying glass and a flashlight to be sure I was matching the right pin to the right color wire.

If anybody needs the adapters in question, look at www.dalco.com and search on "DB9." Dalco is fast and relatively cheap. People who live in California can find the adapters at Fry's Electronics. To go from a nine-pin serial port to Slink-e, you need one M and one F DB-9 to RJ-45 adapter. The Dalco part numbers are 41025 and 41020.

The Slink-e documentation says this will work with up to a 100-foot CAT9 cable. I am using it with a 50-foot cable with no problems.

If you're still intimidated, Dalco will sell you a DB9M to DB9F serial cable for well under $20. The downside is that this cable is harder to run since you have to make holes in the walls big enough to thread a chunky DB9 plug through. You can get the ends of a pre-finished CAT9 cable through a hole well under half an inch in diameter.