Atmel Avr Basics

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University of Florida, EEL 5666 Dr. A. Antonio Arroyo

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Atmel AVR Basics

AVR Studio 5 & XMegaA. A. Arroyo


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OverviewBasic AVR KnowledgeAVR StudioProgramming


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AVR BasicsThe AVR microcontrollers are divided into

three groups: 1.tinyAVR 2.AVR (Classic AVR) 3.mega AVR 4. Xmega AVR

The difference between these devices lies inthe available features. The tinyAVRC areusually devices with lower pin-count or

reduced feature set compared to themegaAVR's. All AVR devices have the sameinstruction set and memory organization.


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AVR Basics AVR's contain SRAM, EEPROM, External SRAMinterface, ADC, Hardware Multiplier, UART, USART,etc. A tinyAVRand a megaAVRstripped off all theperipheral modules, leaves us with the AVR Core the same for all AVRs.

Datasheets are complete technical documents areference on how a given peripheral/feature works.

1.One PageKey information and Feature List2. Architectural Overview3.Peripheral Descriptions4.Memory Programming5.Characteristics6.Register Summary7.Instruction Set Summary8.Packaging Information


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Common Peripherals UART

Provides serial communication interface Typically RS232

Analog/Digital Channels Many sensor are analog 4 channels minimum

SPI/I2C/CAN interfaces Synchronous serial, very common interfaces

JTAG Allows in circuit debugging and programming

ISP

In system programming, serial communication Timers

The more the better PWM / frequency generation modules

Allows hardware generation of motor driving signals


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ATMegaMost popular here at UFKitchen sink of peripherals

UARTS, multi-channel A/D, multiple countersand PWM channels, SPI/I2C/CAN, ISP, JTAG

RISC based 8Bit core16/32MIPS @ 16/32MhzDevelopment Software free from AtmelLarge Hobbyist user base on the internet


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Download doc8067.pdf and doc8077.pdf

Go to www.atmel.com and search for xMega64A1


xMega128A1 Shows available

peripheraldevices and the

ports they use

In IMDL, weextensively use

A/Ds, Timers,and USARTs.


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AVR Studio.

Step 1: Download and Install AVR Studio:http://www.atmel.com/microsite/avr_studio_5/default.asp?

category_id=163&family_id=607

Get AVR 5 with all of the options

Step 2: Read the documentation:http://www.atmel.com/dyn/products/devices.asp?

category_id=163&family_id=607&subfamily_id=1965&source=left_nav


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AVR Studio.Step 1: Create a New ProjectStep 2: Configure Project Settings

What kind of project we want to create, and

setting up filenames and locations.

Step 3: Write your code


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Therearetwowaysengineerswritecodetocontrolaperipheralmoduleonthechip:

1:Copysomeoneelsescode.Thisisfineinthisclassbutwhenitdoesntwork,yourestuck.

2:Writeitfromscratchbyreadingeverywordofthedatasheet.Thismethodgivesyoualotmorecontrolbutcanbefrustratingwhenyoure

unsurehowitshouldwork.{ThisisthewayDr.Arroyodevelopscode.Thisisanotherexampleofbeingthetortoiseandnotthehare}

Using Peripherals


IdeallyinIMDLyourcodeshouldbeacombinationofbothmethods.Ifyoucanfindsomecodetogiveyouastartingpoint,itcansavealotoftime.

Otherwise,dontbeafraidtodigthroughthedatasheet.

Wewillelaborateonhowtogetinformationfromthedatasheet

Using Peripherals


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The three parts you are interested in Overview Description/Features Register Map!

Using Peripherals


Make sure you understand how the peripheralis supposed to work, what pins it uses, whatresources it uses (Timing channels, Ports, etc)

The register map is where you actually seewhich bits to set to configure the peripheral,and which registers to use to interact with the

peripheral

Using Peripherals


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Register name is:

PeripheralName_RegisterName

Peripheral Name from doc8067 Register Name from doc8077

Examples: TCC0_CTRLA, PORTB_OUT,PORTB_DIR

Register Names


Here is the register summary for the USART. Wecan see that serial communication uses 7 regs

1 for Data 1 for status 3 for control 2 for baud rate

Register Names


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TypexmegausartintoGoogle

The first result is a nice 7-page documentexplaining EXACTLY how to set up the serialUSART on the Xmega. The source code for this

example is easily found on the internet.

Find Examples


Important concept: There are two ways towrite/read a pin.

Direct pin access Using a peripheral.

Whenusingdirectpinaccess,usePORTX_INtoreadandPORTX_OUTtowrite.Remembertosetdatadirectionregister,PORTX_DIR.

Sample Code


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Assembly Code Sample


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RobotsinIMDLcanhavemanydifferentstylesofcodeandprogramdesign.

Thisprogrammodelispurelyasuggestion,butithasbeenproventobereliable.

Add#includesandfunctiondefinitions. Insidemain,startbyinitializingallperipheralsyouwill

use.Onlydothisonce.

Haveamainloopthatrunsasfastaspossible(neverslowerthan1Hz,~20Hzisideal)

Writeextrafunctionsoutsideofmain()forspecificbehaviors

Writing C Programs


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#includes

main(){

Initialize LCD, Servos, PWM, A/D, Serial,

DIR, variables

while(1){

read sensors

interpret sensors

function1()

update LCD } // while

} // main

function1() {

stuff } // function 1

Writing C Programs

Atmel Avr Basics

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