Basic Concepts

<< Back to RedEye User Manual On to Opening the Box >> We have tried to structure the RedEye system around the way you actually use your home theater equipment. Even so, sometimes a high-level overview can be helpful. Here is a brief rundown of the philosophy and the basic concepts you'll encounter when using RedEye.

Infrared remote control

Since the 1970's, most wireless remote controls for home theater equipment have relied upon infrared signals. While relatively easy and inexpensive to produce, infrared signals have some drawbacks:
  1. Most infrared remote controls are "one-way" -- that is, they only send signals to the equipment and cannot receive information back from them.
  2. Infrared signals cannot travel through walls or other opaque objects. Often this limitation is referred to as the "line of sight" problem: your equipment must have an unobstructed view of the remote control in order for the system to work. (RedEye mini customers will still need to use “line of sight” to control their devices)
  3. Infrared signals have relatively poor range -- usually between 25 and 50 feet (7.5 to 15 meters).  In addition, sunlight contains large amounts of infrared light can degrade the effective range of an infrared remote.
  4. Infrared signals are "low bandwidth" -- meaning that they cannot send large amounts of information quickly. As a result, they are good for turning the TV off or on, but forget about streaming audio or video.

Radio frequency remote control

Radio frequency remotes also use light waves to send signals, but they use higher frequency microwaves, which gives them certain advantages. Chief among these are the ability to travel through walls, longer range, and wider bandwidth. Although much less common than infrared remotes, radio frequency remote controls have become more popular recently as they have become more affordable. For example, both the Sony Playstation 3 and the Nintendo Wii use radio frequency (Bluetooth) remote controls. RedEye and RedEye Pro systems use both infrared (IR) and radio frequency (RF) signals. The RedEye sends out IR signals to control your home theater equipment. However, in order to overcome the limitations of IR, it communicates with your iOS device using RF signals — specifically, a Wi-Fi network. This combination of IR and RF gives you the best of both worlds: compatibility with a wide array of equipment over IR, and the ability to control your equipment from any room in your house over RF. The RedEye mini functions using only infrared (IR) signals and offers a range of up to about 30 feet, depending on the sensitivity of the equipment you are controlling.

Contact Closure

A contact is basically electronics jargon for a switch. When a contact is closed, the switch is on (current is flowing). When it is open, it is off (current stops). The light switch, the most familiar of control devices, is a simple contact closure apparatus. RedEye Pro provides two types of contact closure. One type is the contact closure sensor – a device which determines when a switch is flipped. For example, this could be tied to a garage door opener, a magnetic strike plate, or something more sophisticated such as a light or humidity sensor. The other type is a contact closure relay – a switch that turns on or off another piece of equipment, such as a pump or a sprinkler system.

Serial (RS-232) control

RedEye Pro is able to interface with devices that use serial communications, specifically the RS-232 standard. RS-232 has been around since the 1960ʼs, when it was developed for the telecommunications industry and used primarily in modems. It generally provides “point-to-point” communication – i.e., a direct connection between two devices. From a control perspective, RS-232 control provides two distinct advantages:
  1. Communication is bi-directional. Not only does this allow feedback to the controller – whether the power is off or on, what the current volume level is, etc – but it also enables error handling so that we can know a command was transmitted successfully.
  2. Data throughput can be much faster. Infrared signals have relatively low bandwidth – with the ability to transmit up to a handful of commands per second – but modern serial communications can move significant amounts of data. Sending images or audio files may not be ideal, but doing so is theoretically possible, at least.
Of course there are downsides to serial control. First, there is no established standard for data formats – the established standard governs only how the data is transmitted, not what it means, so generally we have to write separate serial drivers for each different type of device we wish to control. Second, serial control requires running wires, and the typical DB9-to-DB9 cable is rather thick, bulky, and even a bit pricey.

Internet Protocol (IP) Control

Although it is more sophisticated than control via infrared or contact closure, the RS-232 standard dates back to the 1962 and was originally developed for modems and teletype machines. Since that time, electronic communications have come to be based predominantly on Internet Protocol. It follows that many devices today provide a control mechanism using IP. IP control is similar to RS-232 in that it is bidirectional, but it also has certain advantages. Specifically:
  1. IP is network-oriented. RS-232 is a point-to-point protocol – that is, it connects two machines together directly. By contrast, IP defines a mechanism by which a large number of machines can be interconnected without having to run a physical connection between each pair. For RedEye, the implication is that you can add a virtually unlimited number of IP devices to your system, without ever running out of ports.[1]  And since both RedEye and RedEye Pro are attached to your (IP) network already, it means that you can have the bi-directional capabilities we introduced with RedEye Pro in the more inexpensive and compact RedEye package.
  2. Data throughput is even faster. While we measure RS-232 speeds in thousands of bits per second (kbps), today’s typical Internet speeds are millions of bits per second (Mbps) or even billions of bits per second (Gbps).
  3. More and more devices use IP. Smart TVs, connected Blu-Ray players, streaming media servers, UPnP and DLNA devices – the trend is toward IP control. Infrared control will stay with us because it is inexpensive and simple, but the wave of the future for more advanced control is Internet Protocol.
As with anything, there are certain challenges with IP control. One is networking itself – configuring home networks can be challenging. Another is knowing how to control devices on the network. As with RS-232, IP is a standard which defines the communication pipe – it does not define the specific messages sent over the pipe. There are standardization attempts on top of IP – Universal Plug and Play (UPnP) is one of these – but these are not always used, and adherence to the standard can be inconsistent. As a result, typically building an IP control solution has required some programming knowledge or cobbling together an assortment of standalone applications (one for each device to be controlled).

Devices

A device is a piece of equipment in your home theater system, such as a TV or DVD player. Within the RedEye application you should add a device for each piece of equipment you want to control.

Commands

A command is a bit of functionality that you can use to control a particular device. For example, you might have a command to turn on your TV, and another to turn up the volume.

Activities

An activity is something that you do with your home theater setup, such as Watch a DVD or Listen to an MP3. Activities are a powerful way of grouping functionality from a number of different devices in one place. Because they are based around what you do rather than the different pieces of equipment that you own, activities make it easier to operate complex home theater systems. For example, consider all of the equipment involved in watching a DVD. At the very least you need a television and a DVD player. In many cases, you also have a surround sound system. To watch the DVD, you need to turn on all of these devices and then tune the TV and the sound system to the proper inputs. Then which remote control do you use? You want the TV or sound system remote to change volume, but the DVD remote to access the menu and specific titles. With RedEye activities, one tap on your iOS device turns on everything and presents you with a single button layout so you don't have to juggle remotes. The general idea behind activities is that less is more. Activity button layouts should include only the buttons that you regularly use. Commands that you use less frequently are always available through the "Commands" and "Devices" screens in the application, so there is no need to complicate the button layout by adding them there, as well.

Ports

A port is a place on the RedEye hardware where your device(s) “attach.” On RedEye and RedEye mini, there is only one physical port and it is hidden for simplicity – we control devices using infrared light emitting diodes (LEDs).[2] Ports are more interesting on RedEye Pro, which has 8 infrared ports (which alternatively you can configure for use with sensor devices), 4 relay ports, and 2 RS-232 ports. All these port types mean you can control a wider variety of devices. They also give you more targeted control of individual devices that use the same communication method. For example, what if you have two identical cable boxes stored in the same cabinet? If you blast out infrared light into the cabinet, you will be controlling both devices in sync. Maybe this is acceptable in some kind of “party mode,” but if your intention is to be able to watch one show in the kitchen and different show in the den, then this configuration will not work.[3] If instead of flooding the cabinet with infrared light, however, you use small, targeted infrared emitters, you can run a separate line from each cable box to a different port on RedEye Pro. Doing so allows you to control each box independently.

Rooms

RedEye rooms are analogous to rooms in your house – places where you do things. Typically they have devices, and activities. Inside the RedEye application you can quickly switch between rooms so that you can control devices and activities anywhere in your house. Thus they become a convenient grouping mechanism, “zones of control.” Prior to RedEye Pro, each RedEye unit had the effective range of a single room.[4] You could control more rooms only by adding more RedEye units. However, with RedEye Pro we now have many more ports to which we can attach more devices, so now it makes sense to divide RedEye Pro up into multiple rooms. On RedEye Pro, you define room by the name you give it and a set of ports to which it is “connected.” Often there will be physical cables running from your RedEye Pro to the devices in a particular room, so in practice this definition should be quite close to the real world. The implication of assigning ports to rooms is that all devices attached to that port immediately become part of the room. Similarly, if you move a device to a port outside the room, then the device “disappears” from the room. Of course you can re-use the same port across multiple rooms. This is particularly appropriate for lighting systems and other whole-home devices which would properly be part of each room. Also unique to RedEye Pro is the chance to control from a “whole-house” level, independent of rooms. Specifically, you can select RedEye Pro itself as if it were a room, add whole-house activities, and control any of the devices attached to RedEye Pro. This is particularly useful for multi-zone audio and other such systems that have a “party mode,” as well as true whole-house systems such as lighting and climate control. Thus you might create an “away” activity that selects a certain lighting scene when you are on vacation, or one that turns off all your equipment at bedtime.  

[1] The theoretical maximum number of devices for bi-directional communication is 65,536, but you would run out of space in your home and your RedEye would run out of memory to handle all of those connections long before you hit the limit. [2] Actually, on the gen2 RedEye we also have a physical, 3.5mm (1/8”) infrared out jack. We treat this as the same port as the LEDs because we send the same signal out the jack as we do over the LEDs.
[3] Indeed, for this reason some set-top box manufacturers actually provide as many as 8 alternate IR codesets so that you can individually control otherwise identical equipment. When available, we provide these codes in our database. [4] If you use a RedEye mini to control equipment in more than one location, we recommend naming your devices and activities according to the location – for example, “Bedroom TV” or “Living Room: Listen to Music.”
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