DIY -Drive RGB Led Using ATmega8
Hi…
Here is another experiment to share. An RGB led is a electroluminescent device capable of creating any color by some combination of Red, Green and Blue LED. Actually it is a LED with 3 led’s (red, green & blue) inside one package. RGB led has 4 Legs. The one i have, has one leg for Vcc (Positive Supply) and other three terminals corresponding to R, G and B values. Different color patterns can be generated by controlled PWM Pulses on respective terminals.
From left to right in above picture - 1. RED 2. Vcc 3. GREEN 4. BLUE
Now lets move onto the main part that is How to control using Microcontroller. I am going to use ATmega8l from AVR family for demo. You can use any controller the concept will remain same.
Schematic shown below is just showing the LED connections other connections (Xtal etc) are explicit.
And here is the code that generates almost all combination’s of R G B using PWM over three pins of Mega8l.
PORTC_0 —-Controlling RED
PORTC_1 —-Controlling GREEN
PORTC_2 —-Controlling BLUE
#include"avr/io.h"
#include"util/delay.h"
#include"compat/deprecated.h"
#include"avr/interrupt.h"
unsigned char r=255,g=0,b=0;
ISR(TIMER0_OVF_vect)
{
sbi(PORTC,0);
_delay_ms(255-r);
cbi(PORTC,0);
_delay_ms(r);
sbi(PORTC,1);
_delay_ms(255-g);
cbi(PORTC,1);
_delay_ms(g);
sbi(PORTC,2);
_delay_ms(255-b);
cbi(PORTC,2);
_delay_ms(b);
}
int main(void)
{
DDRC=0xFF; // PORTC as output
PORTC=0xFF; // Initially all leds off no color
TCCR0=0x01; // No prescaling of timer clock
TIMSK=0x01; // Timer Overflow interrupt enable
TCNT0=0;
sei(); // Global interrupt enable
while(1==1) // Infinite loop
{
if(r==255 && g==0 && b==0)
{
r=r-1;g=g+1;
if(g==255 && b==0 && r==0)
{
g=g-1; b=b+1;
if(b==255 && r==0 && g==0)
{
b=b-1;r=r+1;
}
}
}
}
return (0);
}
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