Yenya's World

Tue, 05 Jun 2007

MOXA the Braindead

I hereby declare that MOXA engineers are complete idiots. Pardon my strong wording, and read on why do I think so.

There are many systems for transporting RS-232C serial connection over something else than a standard, but way too big DB-9 (or even DB-25) connector. Since the structured cabling is very common these days, many RS-232C systems use the 8-pin RJ-45 connector for it. However, there is no standard defining the pin assignment for the RJ-45 with RS-232C. For example, Cisco uses its own wiring for their serial consoles, Cyclades has its own, etc. And there is one more problem: RS-232C defines nine signals, while the RJ-45 connector has only eight pins.

Cyclades serial boards, which we have used for a while, employed a quite smart approach to this problem: their expansion boxes were equipped with RJ-50 sockets (RJ-50 is a 10-pin backward compatible variant of RJ-45: the RJ-45 jack can be plugged into the RJ-50 socket, leaving the pins 1 and 10 of RJ-50 unused). Cyclades put all important signals of RS-232C to pins 2 to 9, and they have put a signal "RI" (Ring Indicator), which is rarely used these days, to the pin #1. So almost everybody could use standard RJ-45 connectors and UTP cables, and those who really needed the RI signal could do it using the RJ-50 connector. Unfortunately, Cyclades has been bought by Avocent, and they no longer produce multiport serial boards.

Now MOXA C32081T expansion box uses RJ-50 as well, with 9 pins out of 10 assigned. But guess how "smart" is their pin assignment: they use pin #1 (which is not available when using the RJ-45 connector) for a "DCD" (carrier detect) signal, which is often needed, and they use two other pins (#4 and #7, I think) for a signal ground (GND). And then they state in the documentation, that either of these pins can be used, and it is not necessary to connect both. Moreover, The "RI" signal is not available in their connector. So they have forced their customers to use a completely obscure connector while not using the two more pins to anything meaningful, and still not having a complete set of RS-232C signals.

My dear lazyweb, does anybody know where to buy a pack of RJ-50 connectors and a crimping tool for it?

Section: /computers (RSS feed) | Permanent link | 4 writebacks

4 replies for this story:

Krzysztof wrote: pytanie

czy wiesz moze gdzie dostac RJ-50 connectors?

Yenya wrote: RJ-50

We have bought them at Orange & Green ( But I am afraid they do not offer it through their e-shop. (Sorry, I don't speak Polish, despite my surname; though I can read/understand it to some extent).

dez wrote: about Moxa and Linux

Hey there, I'm not sure whether u're familiar with the Moxa Wireless Embedded Computer series would like to ask a few questions about linux and moxa if I may?

Yenya wrote: Re: about Moxa and Linux

I have not heard about it before, but feel free to ask.

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