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10880 Views 6 Replies Latest reply: Mar 30, 2012 8:59 AM by umadevi RSS
umadevi Novice
umadevi
Currently Being Moderated

Mar 18, 2012 11:02 AM

How to write a program for controlling the brightness of LED using ATMega8 ?

I tried so many times but thats not controling the LED brightness. please help me .....

  • Robert Nelson designspecialist-micro
    Robert Nelson
    68 posts since
    Mar 21, 2011
    Currently Being Moderated
    Mar 19, 2012 11:52 AM (in response to umadevi)
    How to write a program for controlling the brightness of LED using ATMega8 ?

    Hi Umadevi,

     

    What method's have you tried to control the brightness of an LED with the atmega8?

     

    With the atmega8, there's a couple options.. Using the PWM channels, or just using regular i/o with a timing loop turning on/off the port pins..

     

    Regards,

  • richcj10 Novice
    richcj10
    8 posts since
    Mar 26, 2012
    Currently Being Moderated
    Mar 26, 2012 10:29 PM (in response to umadevi)
    How to write a program for controlling the brightness of LED using ATMega8 ?

    Setting up timers are the best. Example code:

     

    #include <avr/io.h>
#include <util/delay.h>

/*
 * Assumptions:
 *      - LEDs connected to PORTB.7 and PORTB.6
 */

int main (void)
{
     /* Waveform Generation Mode 3 - Fast PWM */
     TCCR0A |= _BV(WGM01) | _BV(WGM00);

     /*
      * Compare Output Mode - fast PWM
      * Non-inverting mode drives the output high while the counter
      * is greater than OCRNx. Inverting mode drives the output low
      * while the counter is greater than OCRNx.
      */
     TCCR0A |= _BV(COM0A1) | _BV(COM0A0); /* inverting: fade down */
     TCCR0A |= _BV(COM0B1); /* non-inverting: fade up */

     /* reset all the timers and comparators */
     OCR0A = 0;
     OCR0B = 0;
     TCNT0 = 0;

     /*
      * Clock Source 1 - CLK. Setting this bit late allows us to
      * initialize the registers before the clocks start ticking
      */
     TCCR0B |= _BV(CS00);

     /*
      * Arduino pins 5 & 6 (PORTD.5 and PORTD.6) are PWM driven by TIMER0
      * "The setup of the OC0x should be performed before setting the Data
      * Direction Register for the port pin to output." -- S14.5.3
      */
     DDRD |= _BV(PORTD5) | _BV(PORTD6);

     while (1){
          /*
           * slowly crank up the compare register. since one output
           * is inverting, the net result is to fade from one channel
           * to the other.
           */
          OCR0A++;
          OCR0B++;
          _delay_ms(10); /* busy wait. could be done with timers too. */
     }
     return 0;
}
    • umadevi Novice
      umadevi
      4 posts since
      Mar 18, 2012
      Currently Being Moderated
      Mar 27, 2012 8:48 AM (in response to richcj10)
      How to write a program for controlling the brightness of LED using ATMega8 ?

      Thanking you Richcj,

        But when I executing this program in AVR Sudio4 software it shows 11 errors. I don't know that how we can solve this. Can you suggest me..for how to solve.

      I am sending the errors message what I got while executing..

       

      those are,

       

      Build started 27.3.2012 at 18:55:12

      avr-gcc  -mmcu=atmega8 -Wall -gdwarf-2 -Os -std=gnu99 -funsigned-char -funsigned-bitfields -fpack-struct -fshort-enums -MD -MP -MT control_brightness.o -MF dep/control_brightness.o.d  -c  ../control_brightness.c

      In file included from ../control_brightness.c:2:

      c:/winavr-20090313/lib/gcc/../../avr/include/util/delay.h:85:3: warning: #warning "F_CPU not defined for <util/delay.h>"

      ../control_brightness.c: In function 'main':

      ../control_brightness.c:12: error: 'TCCR0A' undeclared (first use in this function)

      ../control_brightness.c:12: error: (Each undeclared identifier is reported only once

      ../control_brightness.c:12: error: for each function it appears in.)

      ../control_brightness.c:12: error: 'WGM01' undeclared (first use in this function)

      ../control_brightness.c:12: error: 'WGM00' undeclared (first use in this function)

      ../control_brightness.c:20: error: 'COM0A1' undeclared (first use in this function)

      ../control_brightness.c:20: error: 'COM0A0' undeclared (first use in this function)

      ../control_brightness.c:21: error: 'COM0B1' undeclared (first use in this function)

      ../control_brightness.c:24: error: 'OCR0A' undeclared (first use in this function)

      ../control_brightness.c:25: error: 'OCR0B' undeclared (first use in this function)

      ../control_brightness.c:32: error: 'TCCR0B' undeclared (first use in this function)

      make: *** [control_brightness.o] Error 1

      Build failed with 11 errors and 1 warnings...

       

       

      thanking you,

       

      with Regards,

      G. Uma Devi

    • umadevi Novice
      umadevi
      4 posts since
      Mar 18, 2012
      Currently Being Moderated
      Mar 27, 2012 2:57 PM (in response to richcj10)
      How to write a program for controlling the brightness of LED using ATMega8 ?

      may I know which micro controller we can use for this program ? I am using Atmega 8. So I changed the Timer0 as Timer1. Now the program is working. Thank u.

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