Microcontroller - Introduction

Microcontroller

Microcontroller can be termed as a single on chip computer which includes number of peripherals like RAM, EEPROM, Timers etc., required to perform some predefined task.

There are number of popular families of microcontrollers which are used in different applications as per their capability and feasibility to perform the desired task, most common of these are 8051, AVR and PIC microcontrollers.

         

With microcontrollers in general, it is good to know that these little chips are found everywhere. You can find them in microwaves ovens, new applicances, automobiles, televisions, etc. These microcontrollers control and sense the surrounding electronics and environment. For example, microcontrollers can provide output to a display, motor, LEDS, etc., sensing the environment, such as tilt using an accellerometer, light, angular velocity using a MEMS (Microelectromechanical System) gyroscope, sound, encoders for movement, temperature, and button or keyboard input.

To give you a basic understanding of the microcontroller, the AVR Atmega32 microcontroller is considered to be a computer on a chip. The microcontroller is able to execute a set of instructions in the form of a program. The program language that I will be using for theseprojects is C++. To giv ethe usersof this website the best opportunity to learn, the C++ programs will be explained is great detail.

AVR

AVR was developed in the year 1996 by Atmel Corporation. The architecture of AVR was developed by Alf-Egil Bogen and Vegard Wollan. AVR derives its name from its developers and stands for Alf-Egil Bogen Vegard Wollan RISC microcontroller, also known as Advanced Virtual RISC. The AT90S8515 was the first microcontroller which was based on AVR architecture however the first microcontroller to hit the commercial market was AT90S1200 in the year 1997.

AVR microcontrollers are available in three categories:

1.      TinyAVR – Less memory, small size, suitable only for simpler applications

2.      MegaAVR – These are the most popular ones having good amount of memory (upto 256 KB),               higher number of inbuilt peripherals and suitable for moderate to complex applications.

3.      XmegaAVR – Used commercially for complex applications, which require large program memory         and high speed.

The following table compares the above mentioned AVR series of microcontrollers:
 

Series Name	Pins	Flash Memory	Special Feature
TinyAVR	6-32	0.5-8 KB	Small in size
MegaAVR	28-100	4-256KB	Extended peripherals
XmegaAVR	44-100	16-384KB	DMA, Event System included

What’s special about AVR?

They are fast: AVR microcontroller executes most of the instructions in single execution cycle. AVRs are about 4 times faster than PICs, they consume less power and can be operated in different power saving modes. Let’s do the comparison between the three most commonly used families of microcontrollers.

	8051	PIC	AVR
SPEED	Slow	Moderate	Fast
MEMORY	Small	Large	Large
ARCHITECTURE	CISC	RISC	RISC
ADC	Not Present	Inbuilt	Inbuilt
Timers	Inbuilt	Inbuilt	Inbuilt
PWM Channels	Not Present	Inbuilt	Inbuilt