Smart Home Automation with Linux- P4:For every word I’ve written, five have been discarded. Such is the nature of writing. For every ten programs I’ve downloaded, tried, and tested, nine have been discarded. Such is the nature of software. Finding a perspicuous overlap has been a long and arduous tasks, and one that I’d wish for no one to suffer in solitude. | CHAPTER 2 APPLIANCE HACKING There are many Arduino shields on the market most with freely available specifications and circuit diagrams. Each shield has a specific task and includes the following problem domains. Ethernet Networking There is the Arduino Ethernet Shield that supports four concurrent connections working in either client or server mode using TCP or UDP packets. It is based on the Wiznet W5100 chipset and uses digital pins 10-13 to communicate. Wireless Control The main contender here is the Xbee shield which uses the ZigBee wireless protocol meaning it is not directly compatible with existing WiFi connections but can act as a radio transmitter and receiver for basic scenarios and has an indoor range of about 30 meters. Sound The LadyAda Wave shield provides playback support for .wav files up to 16-bit mono 22KHz samples which is a marked improvement over the PCM examples we saw earlier. To handle the problems of memory this shield also supports SD cards provided they re formatted to FAT16 and have all their files in format in the root directory . It is still quite a heavy library however occupying 10KB of flash memory but it is still the best audio solution. It also provides a small power amplifier able to drive 1 8W 8 ohm speakers. This could be used for a talking clock a kitchen-based stopwatch or a virtual pet. Motors Also from LadyAda the motor shield supports medium power control for DC servo and stepper motors. The total number of supported motors and the total power drain are governed by the specific motors themselves but the quoted specs permit you two DC servos on 5V and up to four DC motors two stepper motors or one stepper and up to two DC motors. This shield does utilize a lot pins for control and a lot of power but can be used to lock cat flaps or build a robot. Example The Arduino Welcome Mat With this knowledge you can build a simple circuit write some Arduino software and add a Linux-side script to trigger a piece of speech .
