I'm planning to add an RJ-45 serial port to a device, but which pinout is best?
I know about the Yost style:
And Sun's approach, which is close to Yost.
And the Cisco style, which is sort of inverse:
Is there a "standard" for RJ-45 serial pinouts? (Maybe the most popular stock adapter pinout?) The goal here is to work with serial adapters the user is likely to have in-hand.
Thanks!
Closest standard I know of is EIA/TIA 561
Yep, got that one too (which is different from all of the above, of course). And even the big players are ignoring this spec.
What I'm wondering is... which of these is really more common.
(The EIA spec would be preferred, but if I'm the only guy using it that defeats the goal.)
Thanks!
Quite a few modem and multiport serial board manufacturers use the EIA/TIA 561 spec, so you wouldn't be alone. In my experience, customers frequently make up their own cables anyway using RJ-45 to DB9 or DB25 adapters and straight or flipped RJ-45 extension cables.
IMO, I would think the answer would mainly depend on who would be using your equipment. UNIX sysadmins => Yost; Network admins => Cisco; Building wiring techs => EIA/TIA 561.
If it's a console or "craft" interface to equipment that could be used in a number of applications, you might just want to bite the bullet and supply a cable like the router guys do. That way, you can bring out some special field and production test signals or a secondary RS-232 for development and debugging that is not normally exposed. For example, you might have an embedded processor with two serial ports and you bring both of them to the console or "craft" RJ-45 port. One is the normal console link, while the other is a printf, diagnostic, and autotest access point. That's the approach I've taken on some products.
See
Best of luck
Tom Taylor
Yes, this is the path I'm heading down. I'm leaning toward the YOST DCE spec, which would make it compatible with Cisco / Sun / Yost DB-9 adapters as long as we leave hardware handshaking disabled.
We'd be supplying an adapter, but you know how long those tend to stay near the right equipment - that's what we're trying to work around.
Good trick, thanks. I've been doing something similar for years - it's the only way to keep a field bag compact. Making the cables about 1" long lets you add velcro and stick them all to the main Cat-5 cable for storage.
Thanks!
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