AVR Freaks

#include 

/*
PWM_Servo_ver2
Using PWM to operate HiTec HS-311 Servo
Author:  R. P. Hintze
Date:  16Jan10
Program to operate cause Servo to rotate to extreme positions and 0 degrees
Version 2
Input on P5 thru push button (with debouncing amd interrupt)
Pushing button toggles thru sero settings OFF->FCCW->Center->FCW->OFF
Uses an Atmega8 MCU
*/

//Set includes

#include 
#include 		// need "--std=c99"

//Declare and initialize some variables

typedef unsigned char	u8;

#define KEY_PIN		PINC

#define PC0		0
#define	PC1		1
#define	PC2		2
#define	PC3		3
#define	PC4		4
#define	PC5		5

enum { OFF, FCCW, CENTER, FCW };//for servo_command;
								//OFF->0
								//FCCW->1
								//CENTER->2
								//FCW->3

								
								
u8 key_state;//state of key 1->pressed (active low)
u8 key_press;//detects key press 1->key pressed
u8 key_press_mask;//mask to clear key_press					
u8 servo_command;//holds setting for action servo should take
u8 ct0 = 0xFF; //holder to counter debounce states
u8 ct1 = 0xFF; //holder to counter debounce states

//Declare and define functions

void init_timer1(void);//sets up timer parameters other than OCR1A and CS12:0
void init_timer2(void);//sets up timer parameters other than OCR1A and CS12:0
u8 need_action(u8 key_mask);//determine if key has been pressed

//Start main function

int main (void)
{

//Configure input and output pins

	DDRB |= (1 << 1); //pin PB1(OC1A) set to output
	PORTB &= ~(1 << 1); //initialize as low

	DDRC = 0; //pins PC3, PC4 and PC5 set as input
	PORTC = (1 << PC5) | (1 << PC4) | (1 << PC3); //enable internal pull-up resistors
	
	DDRC |= (1 << PC2); //pin PC2 set to output
	PORTC &= ~(1 << PC2); //initialize as low
	
//Initialize timer1 (OCR1A and CS12:0 not set at this point) and timer2

	init_timer1();
	init_timer2();

//Set up interrupt on timer2

	TIMSK |= (1 << OCIE2); // Enable CTC interrupt on timer2
	sei(); //  Enable global interrupts 


	while (1) //loop to determine if button attached to PC5 pressed and if pressed advance servo_command and trake requisite action
	{		  

		if(need_action((1<<PC5))) //has PC5 been pressed?
		{
			
			servo_command++;  //advance servo_command
			
			servo_command &= ~(0xFC);//if servo_command ->4, resets servo_command to 0
						
		}//end if(need_action...)
		
		switch(servo_command)
		{
			
			case OFF:
			
				TCCR1B &= ~(1 << CS10);//servo is OFF; clear timer
				PORTC |= (1 << PC2); //turn on LED
				break;
				
			case FCCW:
			
				TCCR1B |= (1 << CS10);//servo is on; set up timer1 with no prescaler (Internal RC Oscillator at 1Mhz)
				PORTC &= ~(1 << PC2); //turn off LED
				OCR1A = 0x258; //600 equates into a duty cycle of approx 3% (rotate to -90 degress (left))
				break;
				
			case CENTER:
			
				OCR1A = 0x5DC; //1500 equates into a duty cycle of approx 7.5% (rotate to 0 degress (center))
				break;

			case FCW:
			
				OCR1A = 0x960; //2400 equates into a duty cycle of approx 7.5% (rotate to 0 degress (center))
				break;	
				
		} //end swtich

	} //end while

} //end main
/*********************************/
/*********************************/

//Declare and define functions

/*********************************/
void init_timer1(void)//set all Timer parameters other than OCRA1 and CS12:0 (which are set in main based on input) 
{
	
	TCCR1A |= (1 << COM1A1);//set OC1A (PB1) to clear on Compare Match, and set at BOTTOM (non-iverting mode)
	TCCR1A |= (1 << WGM11);// Configure timer1 for Fast PWM mode (Mode 14)
	TCCR1B |= ((1 << WGM12) | (1 << WGM13));
	ICR1 = 0x4E20; ////Set frequency of timer1 and PWM; 19,999 give a count of 20,000 (TOP +1) which equates into a frequency of 50hz

}//end init_timer1()

/*********************************/
void init_timer2(void)//set all Timer parameters other than OCRA1 and CS12:0 (which are set in main based on input) 
{
	
	TCCR2 |= (1 << WGM21);// Configure timer2 in CTC mode (non-PWM)
	TCCR2 |= ((1 << CS22) | (1 << CS21));//set up timer2 with 256 prescaler (Internal RC Oscillator at 1Mhz)
	OCR2 = 0x27; ////Set caomapre to 39, equates to slightly more than 10ms at prescale of 256
	
}//end init_timer2()

/*********************************/
u8 need_action(u8 key_mask)//determine if key has been pressed
{

	ATOMIC_BLOCK(ATOMIC_FORCEON)
	{
			
		key_press_mask = key_mask;//mask to clear key_press
		key_mask &= key_state & key_press; //read key; has key been pressed?
		key_press &= ~key_press_mask; //reset key_toggle 
						
	}//end ATOMIC_BLOCK(ATOMIC_FORCEON)

	return key_mask;
	
}//end need_action()

/*********************************/
ISR( TIMER2_COMP_vect )
{

	u8 i;

	i = key_state ^ ~KEY_PIN;		// key changed ?
	ct0 = ~( ct0 & i );			// reset or count ct0
	ct1 = ct0 ^ (ct1 & i);		// reset or count ct1
	i &= ct0 & ct1;			// count until roll over ?
	key_state ^= i;			// then toggle debounced state
	key_press |= key_state & i;		// 0->1: key press detect
	
  
}//end ISR()