Configuring Timer0 for PWM generation

It is simple to configure PWM mode in Timer. We just need to set some bits in the TCCR0 register.

TCCR0: Timer Counter Control Register 0

Bit 7- FOC0: Force compare match

Write only bit, which can be used while generating a wave. Writing 1 to this bit will force the wave generator to act as if a compare match has occurred.

Bit 6, 3 - WGM00, WGM01: Waveform Generation Mode

WGM00	WGM01	Timer0 mode selection bit
0	0	Normal
0	1	CTC (Clear timer on Compare Match)
1	0	PWM, Phase correct
1	1	Fast PWM

Bit 5:4 - COM01:00:

1. When WGM00: WGM01= 11 i.e. Fast PWM. Compare Output Mode

waveform generator on OC0 pin

COM01	COM00	Mode Name	Description
0	0	Disconnected	The normal port operation, OC0 disconnected
0	1	Reserved	Reserved
1	0	Non-inverted	Clear OC0 on compare match, set OC0 at TOP
1	1	Inverted PWM	Set OC0 on compare match, clear OC0 at TOP

2. When WGM00: WGM01= 10 i.e. Phase correct PWM. Compare Output Mode

waveform generator on OC0 pin

COM01	COM00	Description
0	0	The normal port operation, OC0 disconnected
0	1	Reserved
1	0	Clear OC0 on compare match when up-counting, set OC0 on compare match when down-counting
1	1	Set OC0 on compare match when up-counting, Clear OC0 on compare match when down-counting

Bit 2:0 - CS02:CS00: Clock Source Select

These bits are used to select a clock source. When CS02: CS00 = 000, then timer is stopped. As it gets a value between 001 to 101, it gets a clock source and starts as the timer.

CS02	CS01	CS00	Description
0	0	0	No clock source (Timer / Counter stopped)
0	0	1	clk (no pre-scaling)
0	1	0	clk / 8
0	1	1	clk / 64
1	0	0	clk / 256
1	0	1	clk / 1024
1	1	0	External clock source on T0 pin. clock on falling edge
1	1	1	External clock source on T0 pin. clock on rising edge.

Fast PWM mode

To set Fast PWM mode, we have to set WGM00: 01= 11. To generate a PWM waveform on the OC0 pin, we need to set COM01:00= 10 or 11.

COM01:00= 10 will generate Noninverting PWM output waveform and COM01:00= 11 will generate Inverting PWM output waveform.

Setting Duty cycle: we have to load value in the OCR0 register to set the duty cycle.

255 value for 100% duty cycle and 0 for 0% duty cycle. Accordingly, if we load value 127 in OCR0, the Duty cycle will be 50%.

Code:

/*
* pwmmotorp1.c
*
* Created: 10-04-2022 16:52:25
* Author : SS
*/

#include <avr/io.h> //we are using I/O registers of AVR
#define F_CPU 16000000L // define the crystal frequency
#include "avr/interrupt.h" // we are using external interrupt pin
#include <util/delay.h> // delay function purpose
#define sw_dir (PIND & (1<<1)) // d1 pin is declared as push button for direction control.
#define sw_dspd (PIND & (1<<2)) // d2 pin is declared as push button for speed control.
#define pw (PINC & (1<<3)) // c3 is declared as push button for power ON/OFF

#define lcd_port PORTB //PORTB pins are for LCD data
#define RS_high PORTD |= (1<<5) // d5 pin is used for Register Select(RS)
#define RS_low PORTD &=~ (1<<5) // d5 pin is used for RS
#define EN_high PORTD |= (1<<6) // d6 pin is used for Enable
#define EN_low PORTD &=~ (1<<6) // d6 pin is used for En.
unsigned char i;

void lcd_cmd(char cmd) //command for lcd display
{
lcd_port = (cmd & 0xf0); //4 bits for 4 bit lcd mode
RS_low;
EN_low;
_delay_ms(1); //after 1ms disable lcd
EN_high; //enable the lcd
lcd_port = ((cmd<<4) & (0xf0)); //lcd port
RS_low;
EN_low;
_delay_ms(1); //after 1ms disable lcd
EN_high; //enable the lcd
}

void lcd_data (char data) //send the data to lcd
{
lcd_port = (data & 0xf0); //4 bits for 4 bit lcd mode
RS_high; //access data register
EN_low;
_delay_ms(1);
EN_high;
lcd_port = ((data<<4) & (0xf0)); //4 bits for 4 bit lcd mode
RS_high; //access data register
EN_low;
_delay_ms(1);
EN_high;
}

void lcd_init()
{
lcd_cmd(0x28);// used for 4 bit lcd mode
_delay_ms(5);
lcd_cmd(0x02); // return home
_delay_ms(5);
lcd_cmd(0x01); // clear screen
_delay_ms(5);
lcd_cmd(0x0C); // display on cursor off
_delay_ms(5);
lcd_cmd(0x06); // increment the display cursor
_delay_ms(5);
lcd_cmd(0x80); // force cursor to begin from 1st line
_delay_ms(5);
}

void cursorpos(char x,char y)
{
if((x<1 || x>2) || (y>16 || y<1 )) //condition will checks the 2 rows and 16 columns
{
x=1; //x= row
y=1; //y= column
}
if(x==1)
{
lcd_cmd(0x7F + y); //{ 80-1 = 7F} for starting the 1st line hex decimal value (80) {y we r using the 7F+y means we need to dtart from that column}
}
else //(x==2)
{

lcd_cmd(0xBF + y); //{0C-1 = 0B} for starting the 2nd line, 2nd row.
}
}

void lcd_out(char x, char y, char *str) //here we are checking which position we want to print
{
cursorpos(x,y);
while(*str)
{
lcd_data(*str);
str++;
}
}

int adc_read(char channel) // we r configuring the adc value
{
unsigned int a, result;
ADMUX = channel; // here we r going to use which channel we need to select in mux here using 2 bit
ADCSRA = 0X80; //control & status register to enable the adc conversion ,enable the interrupt flag, adc interrupt. ADEN=1
ADCH = 0X00; // showing the value 0 or clearing the adc register
ADCL = 0x00; // showing the value 0
ADCSRA |= (1<<6); // to start the conversion 6 bit ADSC high
while((ADCSRA & 0x40) != 0); // when the conversion become zero means conversion of adc (0x40 means interrupted pin )
a= ADCL; //dummy data type a and ais stored the ADCL register (ADC0-ADC7)
result = ADCH; // Store the high value (ADC8-ADC9)
result = result<<8; //to get proper result or alined value we need to do left shift
result = result | a ; // we r adding the ADCL + ADCH to get the 16 bits
return result;
}

int main(void)
{
DDRB = 0XFF; //Declaring all 8-pins as output.
DDRA |= ((1<<0)| (1<<1)); //Declaring A0 & A1 pins as output.
DDRD &=~ (1<<1); //Declaring D1 pin as input.
DDRD &=~ (1<<2); //Declaring D2 pin as input.
DDRD |= (1<<5); //Declaring D5 pin as output.
DDRD |= (1<<6); //Declaring D6 pin as output.
DDRC &=~ (1<<3); //Declaring C3 pin as input.
PORTD |= (1<<2); //enabling internal pull up resistor for D2.
PORTC |= (1<<3); //enabling internal pull up resistor for D3.
i=64; //initializing i=64 because we are running the motor with 25% duty cycle.
TCCR0=0X61; //Non-Inverting mode, PWM phase correct mode,NO prescalar.
GICR=(1<<INT0); //using INT0 for interrupt
MCUCR=0X02; //make interrupt negative edge triggered
sei(); //Enable global interrupt
lcd_init(); //Initialize lcd
/* Replace with your application code */
while (1)
{
while(pw==0) //continue till the push button is released.
{
if(sw_dir == 0) //if the direction control push button is released.
{
PORTA = 0b00000001; // 1 0 to respective 1A 2A pins to rotate in clockwise direction.
lcd_out(1,1,"Motor ON- CL "); //Running clock wise direction

}
else
{
PORTA = 0b00000010; // 1 0 to respective 1A 2A pins to rotate in Anti-Clockwise direction.
lcd_out(1,1,"Motor ON- ACL");

}
OCR0 = i; //i increases in ISR, the corresponding value is to be loaded into OCR0.

}

PORTA = 0x00; // 0 0 to respective 1A 2A pins to Stop rotation.
lcd_out(1,1,"Motor is TURNOFF");
}
}
ISR(INT0_vect) //interrupt service routine
{
i=i+20; // as i increases the duty cycle also increases. i increases by 20 in each push//
// and the corresponding value is to be loaded into OCR0 in while loop//
}

Motor in CLOCKWISE DIRECTION AT25 % DUTY CYCLE

Motor in ANTICLOCKWISE DIRECTION

Dutycycle =60

Duty cycle above 70%