RS232 / TCP converter and BSD.

Martin McCormick martin at
Thu Mar 4 16:20:56 UTC 2010

Olivier GARNIER writes:
> I have a weather station (Lacross WS2350). (can be connect by USB / 
> RS232).
> I want to get data from a FreeBSD server 70 meter from the weather station
> (with software).
> I already have a RJ45 cable between the two objects.
> I wish i could get a RS232 to RJ45 connecter like this one :
> And use it to connect the weather station to the RJ45 network, and then 
> get
> data from my BSD.
> The bad point is that the soft witch are given with the RS232 to RJ45
> translater are for windows, and it make a virtual port on windows.
> I don't know if it will work on BSD.
> If it does not work, i'll be oblige to buy another RJ45 to RS232
> translater... and it's not cheap.

	You did not say what version of FreeBSD you are using
and it does make a difference. The usb port stack was rewritten
for FreeBSD8.0 so that probably works best. I tried to attach a
usb converter to a FreeBSD6.3 system and it never worked.
Different models of RS-232 converters may work fine. I just
could not get these to work at all under 6.3.

	RJ45 plugs and CAT3 or CAT5 Ethernet-style cables are
frequently used to carry RS-232 signals so the only somewhat
unusual device you will need to procure is a plug adaptor such
as one made by Modtap which simply has a RJ45 female on one edge
and a male or female RS-232 9 or 25-pin plug or socket on the
other edge.

	These adaptors have no IC's or intelligence built in to
them. They just route the conductors in the CATx cable to the
right pins. You may have to actually build the adaptor to your
needs but these things at least used to be fairly common.

	The actual RS-232 to usb port converters are relatively
inexpensive these days and they do have processors built in to
them as well as charge pumps to generate the +-12 volts for
RS-232 devices. Some of them are built to work fine under
systems other than Windows boxes and others may only work under
Windows so you will need to be sure that the one you want to use

	So, in short, you need a plug adaptor to make the RJ45
cable useble with RS-232 devices and you also need any of the
common RS-232 to usb converters to actually connect the cable to your
FreeBSD computer.

	As long as the usb-RS-232 converter actually works and
produces a new ttyUSBx device, the brand is not that critical.

Martin McCormick WB5AGZ  Stillwater, OK 
Systems Engineer
OSU Information Technology Department Telecommunications Services Group

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