PWM control LED source code

// Cpu ATTiny13

// Frequency: Internal 9.6000Mhz without frequency division

// winavr gcc optimization level O0

#include

#define nop() __asm__ __volatile__("nop") //Empty statement

unsigned char PWM[]={0x20,0x40,0x60,0x80,0xA0,0xC0,0xE0,0xFF};

unsigned char PWMON;

unsigned char PWMVal;

//IO pin initialization　

void port_init(void)

{

PORTB = 0x08; //PB3 connected button is set to output pull-up

DDRB = 0x37; //PB0 is set to 0 when the PWM output is powered on

}

//Timer0 initialization

//Fast PWM mode frequency 37.500KHz

void timer0_init(void)

{

OCR0A = 0x00;

TCNT0 = 0x01; //Design number

TCCR0A = 0x03; //Set Timer0 to fast PWM mode

TCCR0B = 0x01; //Start Timer0

}

//Delay N milliseconds

void delay_ms(void)

{

unsigned char TempCycA;

unsigned char TempCycB;

for (TempCycA=0; TempCycA<10; TempCycA++)

for (TempCycB=0; TempCycB<90; TempCycB++)

nop();

}

//Main function

int main(void)

{

unsigned int tempval=0;

unsigned int keytime=0;

port_init();

timer0_init();

PWMON = 1; //Initially PWM is on

PWMVal = 0; //First gear

OCR0A = PWM[PWMVal]; //Change the duty cycle

TCCR0A = 0x83; //Turn on PWM

while(1)

{

if (!(PINB&0x08))

{

keytime = 0;

for (tempval=0; tempval<4000; tempval++)

{

if (!(PINB&0x08)) //Key sampling, anti-shake

{

keytime++;

delay_ms();

}

else

break;

}

}

if (PWMON) //When PWM is on

{

if ((keytime>100)&&(keytime<1000)) //Short press 100-1000ms to adjust

{

PWMVal++;

if (PWMVal>7) //Loop

PWMVal = 0;

keytime = 0;

OCR0A = PWM[PWMVal]; //Change the duty cycle

}

if (keytime>2999) //Long press for 3 seconds to turn off

{

PWMON = 0;

keytime = 0;

TCCR0A = 0x03; //Turn off PWM

delay_ms(); //Delay

}

}

else //When PWM is turned off

{

if (keytime>2999) //Long press for 3 seconds to turn on

{

PWMON = 1;

keytime = 0;

TCCR0A = 0x83; //Turn on PWM

}

}

}

}