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Full Discussion: Software controlling serial port pins
Top Forums UNIX for Advanced & Expert Users Software controlling serial port pins Post 302328205 by tigreped on Tuesday 23rd of June 2009 05:33:21 PM
Old 06-23-2009
Question Software controlling serial port pins
Hi. I have a project where I intend to connect a simple Infra-Red circuit to a computer. I must then make a software to control this device via software, i.e., I will not be using microcontrollers in the circuit.

I believe the best way to do it is using the serial port, /dev/ttyS0, and the function ioctl(). The thing is that I've found some code and tried a lot, but none seems to be clear enough or to do exactly what I want.

I understand that out of the 9 pins, there are some that I can't change, like the ground(GND) but seems like the others I can, through some sort of AND and OR operations, using iotcl;

I'm also having some doubts about what is HIGH and LOW because using TIOCMGET it shows some pins are HIGH, and when I test them I check no vcc on them, whereas some indicated as LOW do not have voltage.

Also, there seems to be some default configuration on the ttyS0 port, since with a LED, I touch the negative to the GND(5) and the pins 3 4 and 7 seem to be HIGH, lighting up the LED, while the remaining pins do not light it up.

So, I'm assuming that the pins that by default light the LED are set with HIGH values by the system

By the way, I'm running Ubuntu 9.04, Kernel 2.6.28, GNOME 2.26.1.

So, I would like some neat explanations to help me understand how to use the pins of the serial port to implement this unorthodox and most simple device.

The point is, such device may use GND to as its ground, and some all the time HIGh pin as its VCC, and other 2 pins, one to simply send pulses that will activate the infra-red signal, and other to receive electrical pulses from any infra-red device.

As an end, I desire to use this scheme to comunicate two computers with one of such infra-red serial connected device in each, and to controll the emission and receiving of the bits(pulses) by software.

That will allow me to define my start and end bits, size of word, etc.

Note that it is all didatic end, not much like pratical, but still usefull as a learning process envolving C programming to manipulate serial port and a little bit of electronics.

The circuit schematics is this:
Construíndo um Transmissor Infravermelho Para o seu PC | Clube do Hardware

No one needs to read it in portuguese to understand how to mount it up.

Now, the big challenge is to hook it up to a serial cable connected to the serial port and start programming it. Any, really, any constructive comments will be highly appreciated.
 

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LEARN ABOUT CENTOS

plmpower

plmpower(8)							     powerman							       plmpower(8)

NAME

       plmpower - control Insteon/X10 devices via SmartLabs PLM 2412S

SYNOPSIS

       plmpower --device serial-port

DESCRIPTION

       plmpower is a helper program for powerman which enables communication with Insteon/X10 devices via SmartLabs Power Line Modem, model 2412S.
       It is run interactively by the powerman daemon.	It can also be useful as a standalone tool for debugging X10/Insteon networks based on the
       above device.

NETWORK SETUP

       Note  the  addresses  of  your Insteon/X10 devices.  Plug the PLM into an AC outlet, preferably on the same electrical phase as the devices
       under control.  Devices are available to bridge phases if this is not possible.

       Attach the PLM's serial port to your computer, and ensure that nothing else is using  the  serial  port	such  as  the  system  console	or
       getty(8).  Run plmpower and try the interactive commands below to see if the devices respond reliably.

       Once everything is working, configure powermand to run plmpower as a coprocess as described in powerman.conf(5).

OPTIONS

       -d, --device serial-port
	      Specify the path to the special file connected to the PLM's serial port.

       -t, --timeout msec
	      Set the Insteon timeout to the specified number of milliseconds (default 1000).

       -x, --x10-attempts number
	      Set  the	number of times to run every X10 command (default 3).  X10 does not provide an ACK/NAK mechanism like Insteon so we cannot
	      be certain that any particular X10 command completed, therefore X10 commands are issued multiple times to increase confidence.

INTERACTIVE COMMANDS

       The following commands are accepted at the plmpower> prompt.  Address arguments may be Insteon (e.g. 1A.2B.3C) or X10 (e.g. G12).

       help   Display help on the available commands.

       info   Get info about the PLM.

       reset  Reset the PLM (clears the all-link db).

       on addr
	      Turn on device.

       off addr
	      Turn off device.

       status addr
	      Query status of device (Insteon only).

       ping addr
	      Time round trip request/response to device (Insteon only).

FILES

       /usr/sbin/plmpower
       /etc/powerman/powerman.conf

ORIGIN

       PowerMan was originally developed by Andrew Uselton on LLNL's Linux clusters.  This software is open source and distributed under the terms
       of the GNU GPL.

SEE ALSO

       powerman(1), powermand(8), httppower(8), plmpower(8), vpcd(8), powerman.conf(5), powerman.dev(5), powerman-devices(7).

       http://sourceforge.net/projects/powerman

powerman-2.3.5							    2009-02-09							       plmpower(8)
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