Specifications
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I2C (Inter Integrated Circuit) is a system used when the distance
between the microcontrollers is short and specialized integrated
circuits of of a new generation (receiver and transmitter are usually on
the same printed circuit board). Connection is established via two
conductors- one is used for data transfer whereas another is used for
synchronization (clock signal). As seen in figure, one device is always
the master. It performs addressing of one slave chip (subordinated)
before communication starts. In this way one microcontroller can
communicate with 112 different devices. Baud rate is usually 100 Kb/
sec (standard mode) or 10 Kb/sec (slow baud rate mode). Systems with
the baud rate of 3.4 Mb/sec have recently appeared. The distance
between devices which communicate via an inter-integrated circuit bus is limited to several meters.
SPI (Serial Peripheral Interface Bus) is a system for serial
communication which uses up to four conductors (usually three)- one
for data receiving, one for data sending, one for synchronization and
one (alternatively) for selecting the device to communicate with. It is
full duplex connection, which means that data is sent and received
simultaneously. The maximum baud rate is higher than in I2C
connection.
UART (Universal Asynchronous Receiver/Transmitter)
This connection is asynchronous, which means that a special line for clock signal transmission is not used. In some situations this feature is crucial
(for example, radio connection or infrared waves remote control). Since only one communication line is used, both receiver and transmitter
operate at the same predefined rate in order to maintain necessary synchronization. This is a very simple way of transferring data since it
basically represents conversion of 8-bit data from parallel to serial format. Baud rate is not high up to 1 Mbit/sec.
Oscillator
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