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Microcontrollers were originally programmed only in assembly
language, but various high-level programming languages are now
also in common use to target microcontrollers. These languages
are either designed specially for the purpose, or versions of general
purpose languages such as the C programming language. Microcon-
troller vendors often make tools freely available to make it easier to
adopt their hardware.
The Arduino system provides us with approximately 32K bytes of
flash-memory for sketches programs, which may be programmed in
C programming language.
2.5. Interface Architecture
Microcontrollers usually contain from several to dozens of general
purpose input/output pins (GPIO). GPIO pins are software confi -
gurable to either an input or an output state. When GPIO pins are
configured to an input state, they are often used to read sensors or
external signals. Configured to the output state, GPIO pins can drive
external devices such as LEDs or motors.
Many embedded systems need to read sensors that produce analog
signals. This is the purpose of the analog-to-digital converter (ADC).
Since processors are built to interpret and process digital data, i.e.
1s and 0s, they are not able to do anything with the analog signals
that may be sent to it by a device. So the analog to digital converter
is used to convert the incoming data into a form that the proces-
sor can recognize. A less common feature on some microcontrollers
is a digital-to-analog converter (DAC) that allows the processor to
output analog signals or voltage levels.