Thursday, 12 April 2012

AVR guide for Hobbyists

INTRO



First things first,
 AVR ==> Advanced Virtual RISC 
 RISC ==> Reduced Instruction Set Architecture


As the name suggests, the instructions are simple and all are executed in single Instruction cycle. 

Why should Hobbyists choose AVR?

· Reduced complexity

Easy to use the features available. Consider the timers, there are a number of modes of operation but they are pretty simple to use. 

· Efficient architecture

Highly efficient core with a typical Instruction Cycle of 1MIPS    

· High flash memory (program memory)

With high program memory, more lines of code can be dumped in the flash which is always an advantage. 

· Variety

The AVR family has a lot of variety in it. The pin count of various micros ranges from 8 to 100. So, we are free to choose an AVR uC based on our specific needs. 


Types of 8-bit AVR micros:

1.Tiny

They are small yet powerful. Low power consumption. They are used to shrink the project size in times of space limitations. Typical flash size of 2Kb. 

2.Mega

These are general purpose 8-bit micros with a pin count of 28 to 100pins. Consist of more peripherals and features compared to tiny. 

3.Xmega

These micros are similar to Mega in terms of flash size, pin count etc. But they have better performance than Mega series. In fact X in Xmega refers to Extreme-performance. They have additional features like DMA, Event System etc, which are absent in Mega.




We are gonna work with Atmega8 uC in the fore coming posts. Lets take a look at some of the features of Atmega8 uC.

Features Available:

1.10 bit ADC

It converts analog input given externally at a pin into a digital number of 10 bit length. This number ranges from 0H to 3FFH (in Hex), 0 to 1024 (in dec).The least input voltage that can give 1bit change in the digital number is (Vstep= Vmax/1024) approximately 5mV considering the range of input voltage as 0 to 5V. 

2.PWM generation

3.Highly flexible Timers

4.Internal RC oscillator

5.External and Internal Interrupts

6.TWI(I2C) and SPI interfaces










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