How To [Archive] - Integrators Forum

Dean Roddey

02-04-2004, 12:49 PM

Ok, I'll do a small one on IR control via computer. This will be old news to old timers, but some folks might be confused about how it all works... I'm speaking here from my experience in supporting IR control in the CQC product (www.charmedquark.com), which is a software based control and automation system. This was written pretty much stream of consciousness, so forgive me if it's not completely well organized.

The Big Picture

There are two aspects to IR control via computer, receiving and blasting. The blasting part you would already be familiar with since it's what you do with an IR remote all the time. You are using the IR remote to blast out (through the air in this case) IR signals that are picked up by the appropriate devices. You also experience IR receiving in a way, since the devices you are controlling are receiving those IR signals and reacting to them. But, when a computer is involved, IR receiving also involves treating the computer like a device that can react to IR signals.

IR Blasters

IR blasters allow your computer to send out IR signals just like your IR remote does. The blaster will be connected to the computer via serial, ethernet, or USB or some other connection, via which the computer can tell the blaster to send out signals. You might think that, because of computers being much smarter, that the computers just tells the IR blaster to send out some sequence of bytes and the blaster sends it. But, because of the lack of real standardization in the IR world, computer based blasters generally just work in the same way that your learning remote does. It learns signals and can send them back out again, without really knowing or caring much what the signal is or is doing but, again like a remote, allowing you to apply some human readable label to that signal to make it obvious what it does.

Unlike a learning remote, the computer (and some of the smarter remotes like Prontos and whatnot) can also get IR signals into it by just loading up data files which were learned into the blaster by someone else and saved out to file. This is a big advantage in that it allows much easier swapping around of IR signal data. CQC groups a set of IR signals for a particular device into a file called an 'IR device model', and these can be exported to an XML format and sent to another CQC user who can import it into their system. We provide a library of these device model files on the web site for people to download and import into their system.

Some blasters have no learning capability and depend completely on the ability to import data files into the software that controls them. In many cases they can import Pronto format IR data, so you can get IR files from places like remotecentral.com and use them. Just be forewarned that the files on Remote Central are often full of junk and not well done. You often have to try a few different files to get one that will work for you.

Blasters come in two primary variations, open air blasters and wired blasters. Open air blasters are like your IR remote control and just blast out into the open air. This is usually fine, but it can be a problem for a number of reasons. For one, it can be hard to position it correctly to hit the devices. If the computer is in the rack with the devices, then you usually have to depend on the signal bouncing off the opposite wall and back to the devices, which sometimes won't work. Another reason can be that you have more than one device of the same model and want to control them separately, which won't work if they all react to the same signal.

So you can also get wired blasters that send their signal out through a cable to a little blaster that you stick on the front of the device directly on its IR sensor. Technically of course this is still an open air blaster but it avoids the above problems. Some devices also will take that signal directly without ever going into the open air though. More importanly, these types of blasters can support multiple 'zones', meaning that they can have multiple separate blasters which can directly talk to specific devices, so they are often called 'zoned IR blasters'.

IR Recievers

Another nice use for IR in the computer environment is to use an 'IR receiver' device, which connects to the computer in ways similar to the blaster, and in many cases is the same device since there are a number of IR blaster/receiver combo devices. The reason for the receiver is to make the computer do things in response to an IR signal. You might wonder what the point is since you can just send the signals directly to the devices, but it's not just to pass IR signals through the computer, but to tell the computer to take some action that can do a lot more than just send the same IR signal through.

In CQC, you 'train' CQC just like you would train a learning remote, but once you've trained it to recognize an IR signal, you then associate that signal with an 'event', which is a configured set of actions that will be invoked when CQC sees that signal via the IR receiver. In my case, for instance, I can press a button on the remote and CQC will turn on the projector, turn on the A/V processor, and the video switcher, and the DVD player, start the lights dimming, select the DVD input on the video switcher and processor, and by the time it's up and running have the lights totally off, all just from a touch of a remote control button.

Since CQC is network distributed, it can control devices throughout the home, so an IR button pressed in one room can cause things to happen anywhere else in the home where CQC has control of devices, so it can put a lot of power at your finger tips in an easy to understand and carry IR remote. This also means it can do a form of 'IR Distribution' since a button press here can cause IR blasters over there to spit out signals. But it's not IR distribution in the traditional sense which just passes signals as is over intermediary wired channels to another blaster.

CQC offers other ways of invoking those same events, such as via a drawn user interface or a keyboard key, but it's often convenient to be able to invoke them from an IR remote in the dark of a home theater or when in the bed.

Examples

One of the most popular IR blaster/receiver devices these days is the USB-UIRT (www.usbuirt.com) which is a USB based device (as you'd probably guess) which does both receiving and open air blasting. It has a powerful blaster so it is usually pretty flexible in terms of placement. It is inexpensive and widely used so it's a safe choice.

Another option is the Global Cache GC-100 (www.globalcache.com), which is an ethernet based device that can do zoned IR blasting, with a variable number of zones according to how you configure it. Each of the zones can also be configured as a sensor that can pick up LED lights being on or off and make that available to the control system as a 'power on/off' indicator, which is otherwise not available from IR controlled devices.

The IRMan is an inexpensive and widely used IR receiver. It is a serially based device (RS-232). If have some other blaster, or you just need receiving in a particular location, the IRMan is a good choice.

CQC IR Control

You can read about how to use IR via CQC on the Using IR (http://www.charmedquark.com/GetStarted/UsingIR.htm) page. It explains some of the above, but provides more CQC specific information. CQC uses a single generic IR driver archticture, and supports the USB-UIRT, IRMan, GC-100, Ira-2, and RedRat2.

Note that CQC is primarily oriented towards 'hard wired' devices (serial, socket, USB, etc...), since they provide two way control and are much more robust control mechansisms. So I don't want you to get the idea that CQC is an IR control system. It is a full featured, general purpose control and automation software suite. I just discussed the IR related support here because that is the subject of this mini-tutorial.