Hardware Reference
In-Depth Information
Remote-Control Methods
Your house will come alive with the sound of music. Until you've lived with music in every room, you cannot imagine
the difference that this makes. Being able to change the volume is nice, but not necessary, because each album is
normalized to be consistent within itself. However, if you're randomizing the tracks, then the volume can vary wildly,
necessitating a local volume control. And if you're introducing such functionality, you'll often want more involved
local control to skip those random tracks you don't want to hear. Such functionality requires more hardware.
Direct Control
Standard HiFi equipment is invariably supplied with an IR remote, making it possible to place an IR relay receiver in each
room and line up its transmitter with the receiver eye on the device. Small receivers can be mounted in-wall alongside,
or instead of, a light switch and be powered by batteries. Adventurous developers can utilize a cheap all-in-one remote
control and incorporate its workings, along with an IR relay and replacement switches, into their own wall unit.
Relay Control
Although few consumer products come with anything other than IR, this doesn't mean that you have to control it with
IR, provided that there is something in between that understands both protocols.
Bluetooth, for example, is found on all current mobile phones, and although it is slightly power-hungry, there are
many free or nearly free applications that interface with a suitably equipped PC. And because many people carry a
phone on them at all times, this provides a very accessible way of providing control.
All Bluetooth communication requires a Bluetooth address. This looks like a MAC address from traditional
network scenarios and can be discovered with the following:
hcitool scan
Note that there is a slight delay in scanning the area for devices, and a further delay is realizing when it has
disappeared! So although this program
can
be used to determine when the Bluetooth signal is coming back into range
(and therefore when you are returning home), it is best to perform a directed scan for a single phone using
bluemon
.
Bluetooth control apps come in two halves, one for the PC and one for the mobile. The mobile side is usually
Java-based but, despite its “write once-run anywhere” mantra, usually needs a version specific to your phone because
of the vagaries of mobile development. The messages sent are usually in a protocol that the receiving PC app can
process. This is then configured to send a suitable IR signal to the device in question that might be to control the
media player currently running on the PC or lock the desktop screen should the Bluetooth signal fall out of range.
10
Vectir provides such functionality for Windows users, while those in the Linux community can choose packages
11
such
as Remuco, Amarok, or RemoteJ. There are other packages to permit file transfers between phones and PCs, such as
obexftp
, but these are suited to syncing applications and therefore are outside the scope of this topic.
X10 provides a similar mechanism for relayed control. Utilizing a handheld transmitter module (such as the
HR10U), you can send an X10 message (such as lamp E10 on) to the RF-to-X10 gateway, which places the data on the
power lines. Your PC can then listen for this particular message and control the media player, either by retransmitting
an IR signal or by affecting the PC-based software. I'll cover the specific mechanics of this when looking at Cosmic in
Chapter 7, which supports a full range of additional functionality.
4HISISONEOFTHEPRESTATEDAIMSOFTHE
bluemon
PACKAGE
!COMPLETELISTWOULDBEIMPOSSIBLEHEREBUTALTERNATIVESINCLUDE
http://tuxmobil.org/bluetooth_cell_apps.html
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