Communication: Humans Talk. Computers Talk - Smart Home Automation with Linux and Raspberry Pi - page 151

the (near) free cost of the Internet to provide financial savings and, when combined with mobile technology,
facilitate the amusing situation in which using a mobile phone is used to order pizza online through a web page!
When we talk of computer-to-human communication, we are looking at reports and information about the house
that the computer sends to us, as appropriate. In the simplest of cases, this might be the daily wakeup call or an e-mail
containing the day's TV schedule. In more complex scenarios, it could be a full report of the computers in the house
and how they are performing. 3
And, finally, human-to-computer communication takes place most often and involves us telling the machine what
we want to do via e-mail, SMS, or a web page. To be a truly smart and automated house, this list would include haptic
interfaces. We don't need to issue an explicit command to tell the computer what to do; it knows what to do by studying
the environment. For example, the computer would know to switch on the lights when the front door has been opened;
shortly afterward, the inside doormat sensor will close because it had realized that someone is entering the house.
You've already built similar haptic functionality in Chapter 2, so I'll cover explicit communications in this chapter.
IP Telephony
IP telephony or VoIP communications are commonplace and an expected feature of any smart home. For most,
however, a VoIP installation will be a private one, existing only on personal laptops or desktop machines as a result of
the personal nature of phone communication. But it can be used in combination with voice recognition to provide an
intriguing (albeit error-prone) means of data input and a way to add an internal home intercom system.
Skype
In the same way that Hoover has become synonymous with vacuum cleaner and Google now is a verb meaning to
search, Skype is the byword for VoIP. Begun in 2003 and released as freeware, Skype has provided clients for Linux,
Mac, and Windows, each with varying degrees of functionality and with all versions allowing you to make free calls to
other Skype users and subsidized voice calls to mobile numbers and landlines, like any standard phone. Most allow
you to log in with the same account from several different locations, meaning that you can install Skype onto each
terminal in the house with the same house-oriented phone number so that you can send and receive calls from any
room in the house. With additional hardware, you can adopt a hands-free approach, moving between rooms during
the conversation, such as to check on dinner, for example, returning you to the roaming possibilities that have existed
since the introduction of cordless phones in the 1980s!
Asterisk
Asterisk is another software-based phone solution that also includes support for VoIP, mobile, and landline calls. Its
benefit to us is that it is free software in the truest sense of the word and can support many protocols, because it is a
full private branch exchange (PBX) and can support highly configurable call forwarding, voice mail, conferencing, and
phone menus (so you can implement your own “Press 1 to turn your lights on” system!). As with Skype, you will need
a service-providing gateway to connect the IP-based protocols to the phone network in general. This is a
paid-for service and can be bought from many places, including Skype itself with its own Skype-to-Asterisk module.
As an alternative, FXO interfaces are available which let you interface SIP to PSTN. You'll still have to buy the FXO
interface (for around $15), but you won't need to purchase from anyone other than your phone provider.
The simplest way to install the mass of code that is Asterisk is currently through FreePBX, but even that is only
worth the time if you have a large enough house to make shouting an impossibility or you're keen users of the phone,
as you can get more solid communication through e-mail or the web (now both available on most phones) or SMS.
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