Embedded Computing System(06CS74)
UNIT - 3
DEVICES - 2, COMMUNICATION BUSES FOR DEVICE NETWORKS:
Wireless devices
Timer and counting devices
Watchdog timer; Real time clock
Networked embedded systems
Serial bus communication protocols
Parallel bus device protocols
Internet enabled systems
Wireless and mobile system protocols.
6 Hours
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Wireless devices, Timer and counting devices
Software Timer
i> A timer is a specialized type of clock. A timer can be used to control the sequence of an
event or process. Whereas a stopwatch counts upwards from zero for measuring elapsed
time, a timer counts down from a specified time interval, like an hourglass. Timers can be
mechanical, electromechanical, electronic (quartz), or even software as all modern computers
include digital timers of one kind or another. When the set period expires some timers simply
indicate so (e.g., by an audible signal), while others operate electrical switches.
ii>Watchdog timer
A watchdog timer (or computer operating properly (COP) timer) is a computer hardware
or software timer that triggers a system reset or other corrective action if the main program,
due to some fault condition, such as a hang, neglects to regularly service the watchdog
(writing a "service pulse" to it, also referred to as "kicking the dog", ―
petting the dog‖,
"feeding the watchdog"[1] or "waking the watchdog"). The intention is to bring the system
back from the nonresponsive state into normal operation
iii>RTC(Real time clock
Timer functions
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I2C bus protocol.
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Wireless and mobile system protocols
Bluetooth
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ZigBee
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