Counter/Timer/PWM

Counter/Timer/PWM

incoming Lab.incoming Lab.

Counter

counter is a device which stores the number of times a particular event or process has occurred

synchronous/asynchronous pulseup counter/down Counter

D C B A

0 0 0 0 0

0 0 0 1 1

0 0 1 0 2

0 0 1 1 3

0 1 0 0 4

0 1 0 1 5

0 1 1 0 6count 범위 : 0~2N-1


Timer

timer is a specialized type of clocksynchronous counter with fixed frequency clock

Tclk = 1/fclk D C B A

0 0 0 0 0 0

0 0 0 1 1 Tclk

0 0 1 0 2 2Tclk

0 0 1 1 3 3Tclk

0 1 0 0 4 4Tclk

0 1 0 1 5 5Tclk

0 1 1 0 6 6TclkTimer 의 최소단위 : Tclk

최대 측정 시간 : (2N-1)Tclk


Example

counter : how many tablet ? timer : how long ?


Counter/Timer in Atmega128

8-bit Timer/CounterTCNT0, TCNT2Counting 범위 : 0~255

16-bit Timer/CounterTCNT1H & TCNT1L, TCNT3H & TCNT3LCounting 범위 : 0~216 – 1 = 65535


8-bit Timer/Counter Block Diagram


Basic Operation

prescaler

Counter/timer (TCNTn)

clk

fclk

Tclk = 1/fclk

8 bit / 16 bit

ftimer = fclk/N

Ttimer = N/fclk

fclk = 1 Mhz, N(prescale) = 100Tclk = 1 uSec

ftimer = fclk/N = 10 kHz

Ttimer = 100 uSec


Basic Operation & Timer Interrupt

normal mode : overflow interrupt

clear time on compare match (CTC) mode : output compare interrupt

숫자세기구간

0 TCNTn

255

인터럽트 발생위치

(초기값)

숫자세기구간

0

OCRn

255


(한계값)

clkf

NT )-0xFF( 초기값

clkf

NOCRnT


8 bit Timer/Counter Register 관련 Register

TCCRn : Timer/Counter Control Register

예 ) TCCR0 = 0x05 ftimer = fclk /128 = 7372800/128 = 57600 Hz

Ttimer = 1/57600



TCNTn : Timer/Counter Register

Overflow Interrupt예 ) TCNT0 = 0x27

구간 = 0xFF-0x27 = 0xD8 = 216 216 * Ttimer 마다 인터럽트 발생이 가능함

숫자세기구간

0 TCNTn

255


(초기값)



OCRn : Output Compare Register

Output Compare Interrupt예 ) OCR0 = 0xA2

구간 = 0xA2 = 162 162 * Ttimer 마다 인터럽트 발생이 가능함

숫자세기구간

0

OCRn

255


(한계값)



TIMSK : Timer/Counter Interrupt Mask Register

TOIE0 bit : Overflow Interrupt EnableOCIE0 bit : Output Compare Interrupt Enable

ETIMSK : Extended Timer/Counter Interrupt Mask Register


16-bit Timer/Counter Block Diagram



Timer/Counter Control RegisterTCCRnA

TCCRnB

TCCRnC



Clock Selection Bit : CSn0 ~ CSn2 in TCCRnB



TCNTnH & TCNTnL

숫자세기구간

0 TCNTn

ㅗㅗ

0xFFFF


(초기값)



Output Compare RegisterOCRnAH & OCRnAH OCRnBH & OCRnBHOCRnCH & OCRnCH

숫자세기구간

0

OCRn

0xFFFF


(한계값)


Timer Interrupt Example

Mode : normal mode (overflow interrupt)Interrupt 간격 : 500mSec

fclk = 7372800 Hz 0.5 초 : 3686400 16bit counter = 216 – 1 = 65535

prescale : 1024 3686400/1024 = 3600 => 0xE10 0xFFFF-0xE10 = 0xF1EF

TCCR1A = 0x00; TCCR1B = 0x05; TCCR1C = 0x00;TCNT1H = 0xF1; TCNT1L = 0xEF;TIMSK = 0x04;



#include <avr/io.h>#include <avr/interrupt.h>

int main(){DDRD = 0x18;

TCCR1A = 0x00; TCCR1B = 0x05; TCCR1C = 0x00;

TCNT1H = 0xF1; TCNT1L = 0xEF;

TIMSK = 0x04;sei();

while(1); return 0;}


Timer Interrupt Service Routine

ISR(TIMER1_OVF_vect){ static char cnt = 0; // static 은 이전 값을 유지 함

cnt++; cnt %= 2;

if( cnt == 0 ) PORTD &= 0xEF; else PORTD |= 0x10;

TCNT1H = 0xF1; TCNT1L = 0xEF;}


연습

다양한 시간으로 lamp 구동1 초 간격으로

left motor 전진 right motor 전진left motor 정지left motor 후진right motor 정지right motor 후진left motor 정지right motor 정지이하 반복


Timer Interrupt Example (II)

Mode : clear time on compare match (CTC) mode (output compare interrupt)Interrupt 간격 : 250mSec

fclk = 7372800 Hz 0.25 초 : 1843200 16bit counter = 216 – 1 = 65535

prescale : 1024 1843200 /1024 = 1800 => 0x0708

TCCR1A = 0x00; TCCR1B = 0x0D; TCCR1C = 0x00;OCR1A =0x0708; (OCR1AH = 0x07; OCR1AL = 0x08; )TIMSK = 0x10;


CTC mode (output compare interrupt)

Which counter ?TCNT0, TCNT1, TCNT2, TCNT3 ?

Timer/Counter Control RegisterTCCRnA / TCCRnB / TCCRnC = ?

Output Compare RegisterOCRnA / OCRnB / OCRnC = ?

Timer/Counter Interrupt Mask RegisterTIMSK ?

숫자세기구간

0

OCRn

0xFFFF


(한계값)



Timer/Counter Control RegisterTCCRnA

TCCRnB

TCCRnC

prescale

Timer/counter mode

0 0

0 1 1 0 1



Timer/counter Mode of Operation



Output Compare RegisterOCRnA / OCRnB / OCRnC = ?

TIMSK : Timer/Counter Interrupt Mask Register



#include <avr/io.h>#include <avr/interrupt.h>

int main(){DDRD = 0x18;

TCCR1A = 0x00; TCCR1B = 0x0D; TCCR1C = 0x00;

OCR1A = 0x0708

TIMSK = 0x10;sei();

while(1); return 0;}


Timer Interrupt Service Routine

ISR(TIMER1_COMPA_vect){ static char cnt = 0; // static 은 이전 값을 유지 함

cnt++; cnt %= 2;

if( cnt == 0 ) PORTD &= 0xEF; else PORTD |= 0x10;

}


Timer/Counter 의 Input & Output

InputCounter : asynchronous pulseTimer : external clock

OutputWaveform PWM : Pulse Width Modulation

External Input/OutputI/O Port 에 배정


Timer/Counter 의 Input & Output

TCNT0 : 8bit CounterNo inputOutput : OC0 (PB4)

TCNT1 : 16bit CounterInput : T1 (PD6)Output : OC1A(PB5), OC1B (PB6), OC1C(PB7)

TCNT2 : 8bit CounterInput : T2(PD7)Output : OC2 (PB7)

TCNT3 : 16bit CounterInput : T3 (PE6)Output : OC3A(PE3), OC3B (PE4), OC3C(PE5)


Timer/Count Mode

normal mode : overflow interruptclear time on compare match (CTC) mode : output compare interruptFast PWM Mode

숫자세기구간

0

OCRn

255


(한계값)


Timer/Count Mode

Phase Correct PWM Mode

숫자세기구간

0

OCRn

255


(한계값)



DC 모터의 가감속 제어

DC 모터의 속도제어DC 모터의 전달함수

정상 상태 속도는 입력 전압에 비례

Ks

K

sV

s

a

gain DC1)(

)(

+V

DC모터

0V

Vce가높다+

-


Pulse Width Modulation (PWM, 펄스폭 변조 )

commonly used technique for controlling power to an electrical device

power delivery, voltage regulation, telecommunication, …

신호 크기에 비례하는 pulse width or duty cycle

(%)duty 100TtW

0

0duty

V max25.0

%25duty

VV

max5.0

%50duty

VV

max75.0

%75duty

VV

max

%100duty

VV


Pulse Width Modulation (PWM, 펄스폭 변조 )

Why PWM ?difficult to amplify a voltage with appropriate powercompact and low cost means for applying adjustable power for many devices

Principle of PWM전달되는 power 는 duty cycle 에 비례

PWM frequency

2max

2

max0

2max0

2 1)(

1

VT

tV

VT

tdtV

Tdttv

TV

Wrms

WtT

rms

W

Tf pwm /1


PWM in ATmega128

Fast PWM mode/Phase Correct PWM ModeTCNT0

OC0 (PB4)TCNT1

OC1A(PB5), OC1B (PB6), OC1C(PB7)TCNT2

OC2 (PB7)TCNT3 : 16bit Counter

OC3A(PE3), OC3B (PE4), OC3C(PE5)

OC1B (PB6) : Left Motor EnableOC1C (PB7) : Right Motor EnableTCNT1 => PWM 으로 사용


PWM Example

PWM mode : Fast PWM 10 bit modePWM frequency

motor 와 motor driver 의 주파수 특성 : ?fclk = 7372800 Hz

N(prescale) = 8 TOP = 210-1

숫자세기구간

0

OCRn

255


(한계값)

HzTOPN

ff clkpwm 900

)1(


PWM Example


PWM Example

Timer/Counter Control Register

TCCRnA

TCCRnB

TCCRnC

prescale

Timer/counter mode

1 1

0 1 0 1 0

1 0 1 0


PWM Example


PWM Example

#include <avr/io.h>

int main(){

DDRB = 0xCF; PORTB = 0x06;

TCCR1A = 0x2B; TCCR1B = 0x0A; TCCR1C = 0x00;

OCR1B = 0x00; /* 원하는 속도를 기입 0x000 ~ 0x3FF */OCR1C = 0x00; /* 원하는 속도를 기입 0x000 ~ 0x3FF */

while(1);return 0;

}


실습 과제

좌우 모터에 대해저속 /중속 /고속을 정의전진 /후진 /정지를 정의Left/Right Switch 를 이용하여 Motor Disable (Interrupt)USART 통신을 이용하여 제어 (Interrupt)

Date post:	13-Jan-2016
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Counter/Timer/PWM

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