From: "Carlo E. Prelz" <fluido@...>
Date: 2012-12-19T18:34:33+09:00
Subject: Re: Comunication via rs485

	Subject: Comunication via rs485
	Date: Wed 19 Dec 12 05:39:15PM +0900

Quoting iosu bueno (lists@ruby-forum.com):

> Is there any way to comunicate via rs485 with ruby? Any gem or project
> already made by someone? I need to do that in m project and id like to
> do it with Ruby instead of using a conversor to read rs232.

Back in 2009 I needed to talk to a device via rs485. Eventually, due
to the distance to the device, I had to use a gizmo that converted the
conversation to ethernet-based. But while I tested the code I had the
device on my desk, and thus talked native rs485. Well, once my serial
port was properly configured to talk rs485 (in my case I needed to
change the position of a few hardware jumpers on the PCI board) I
talked to the port as I would to any other serial port. before opening
the port I called stty as follows

system("stty -F /dev/#{@dev} speed #{@speed}  -brkint -icrnl -imaxbel -opost \
-onlcr -isig -icanon -iexten -echo -echoe -echok -echoctl \
-echoke ignbrk -ixon -ixoff hupcl"

(where @dev was the appropriate ttySxx, and the speed was the expected
comms speed). Then I opened the unit as follows:

@unit=File::open('/dev/'+@dev,File::RDWR)

and I would use @unit.syswrite and @unit.sysread as normal.

It was the first and last time I had to do with rs485. I was VERY
happy that everything worked, that's for sure. Now I do not even have
that PCI card anymore, so I cannot give you much more advice.

HTH

Carlo

-- 
  *         Se la Strada e la sua Virtu' non fossero state messe da parte,
* K * Carlo E. Prelz - fluido@fluido.as             che bisogno ci sarebbe
  *               di parlare tanto di amore e di rettitudine? (Chuang-Tzu)