di3011.txt
;*******************************************************************************************************
;
; LISTING 1 - MOTOR-CONTROL C LISTING
;
; "AVR microcontroller makes improved motor controller," EDN, October 17, 2002, pg 98
;
;*******************************************************************************************************

#include <io.h>
#include <interrupt.h>
#include <signal.h>

unsigned char c17;			//Used to indicate the present direction of motion.
unsigned short s23;			//Used to hold the 16 bit Timer 1 count.

SIGNAL(SIG_INTERRUPT4)
{
volatile unsigned char ptr;
unsigned char lower_byte;
unsigned char upper_byte;

	lower_byte = 0;		//Clear bytes in anticipation of receiving
	upper_byte = 0;		//new data.
	c17 |= 0x04;			//Set global for control is with receiver.
	ptr = inp(EICR);		//Get present state of EICR.
	if ((ptr & 0x01) == 0)		//If falling edge capture enabled, then ...
	{
		c17 |= 0x08;			//Indicate arithmetic operation can proceed
		lower_byte = inp(TCNT1L);	//Move low part of count to low byte.
		upper_byte = inp(TCNT1H);	//Move high part to high byte.
		s23 = upper_byte;		//Create 16 bit word that represents period
		s23 <<= 8;			//of pulse.
		s23 += lower_byte;
	}
	else					//If rising edge capture enabled, then ...
	{
		c17 &= 0xF7;			//Indicate arithmetic operation should wait
		outp(0,TCNT1H);		//Reset timer counter register.
		outp(0,TCNT1L);		//When writing to 16 bit timer, must write
	}					//to upper register first.
	ptr = inp(EICR);			//Change state of last bit of EICR 
	ptr ^= 1;				//in order to be able to trap on the 
	outp(ptr,EICR);			//opposite edge.
}

int initialize(void);
int receiver_cntrl(void);

int main(void)
{

	initialize();				//Call initialize in order to set
						//up registers and peripherals.
	s23 = 0;				//Initialize useful variables,
	c17 = 0;				//some that are global and some
						//that are local to main.		
	while (1)
	{
		receiver_cntrl();		
	}
}
int initialize(void)
{
	//Timer 0 Setup Code
	outp(0x61,TCCR0);	//No prescale to clk, enable PWM, clear PWM output
	outp(0,OCR0);		//Set output compare register to 0.
	outp(0,TCNT0);		//Set timer counter to 0.
	//Timer 1 Setup Code		
	outp(0,TCCR1A);	//Set clk source as clk/8, compare timer to overflow
	outp(0x0A, TCCR1B);	//Set output compare register to 0xFF00.
	outp(0xFF, OCR1AH);	//Not used, however.
	outp(0,OCR1AL);	//Set output compare register to 0.
	outp(0,TCNT1H);	//Set timer 1 counter to 0.
	outp(0,TCNT1L);		
	outp(0x10,TIMSK);	//Enable timer overflow interrupt.
	//Timer 2 Setup Code
	outp(0x61,TCCR2);	//No prescale to clk, enable PWM, clear PWM output
	outp(0,OCR2);		//Set output compare register to 0.
	outp(0,TCNT2);		//Set timer counter to 0.
	//External Interrupts Setup Code
	outp(0x10,EIMSK);	//Enable interrupts for externals 0 through 4.
	outp(0x03,EICR);	//The rising edge between two samples of INT4 
				//generates an interrupt.
	outp(0x80,ACSR);	//Disable comparator.
	//Port B Setup Code	
	outp(0xff,DDRB);	//Set initial direction of port pins to output.
	outp(0,PORTB);		//Set initial state of pins.
	//Port D Setup Code
	outp(0x0,DDRD);	//Set initial direction of port pins to input.
	outp(0xff,PORTD);	//Set initial state of pins.
	//Port E Setup Code
	outp(0,DDRE);		//Set initial direction of port pins to input.
	outp(0,PORTE);		//Set initial state of pins.
	
	sei();			//Globally enable all active interrupts.
	
	return(0);
}
int receiver_cntrl(void)
{
volatile unsigned char ptr;

	c17 &= 0xF7;		//Enable receiver mode
	s23 -= 0x01EE;		//Set up map range
	if ((s23 >= 0xF0) && (s23 <= 0x110))	//See if s23 is in the deadband.
	{				//If so, then stop the motor.
		ptr = inp(PORTB);	//Get present state of output drivers.
		ptr &= 0xDB;	//Block movement by setting PB:2 and PB:5 to 0
		outp(ptr,PORTB);	//Update state of driver.
		outp(0,OCR0);	//Set PWM0 to 0% disabling forward.
		outp(0,OCR2);	//Set PWM2 to 0% disabling reverse.
		c17 &= 0xFC;	//Modify global to indicate direction is stop.
	}
	else if ((s23 > 0x110) && (s23 <= 0x1FF))	//See if s23 is in fwd range	
	{						//If so, then proceed with fwd.
		if ((c17 | 0xFD) == 0xFD)		//If global indicates present 
		{				//direction is not reverse. then ...
			outp(0,OCR2); 	//Block reverse by shutting down PWM2.
			ptr = inp(PORTB);	//Get present value of port B.
			ptr &= 0xDF;	//Stop reverse by setting driver to 0.
			outp(ptr, PORTB);	//Update value of port B.
			ptr = (volatile unsigned char)s23; //Assign movement to ptr.
			outp(ptr, OCR0);	//Assign PWM to new movement value.
			ptr = inp(PORTB);	//Get present state of port B.
			ptr |= 0x04;	//Indicate that the direction is forward.
			outp(ptr,PORTB);	//Update the value of the port.
			c17 |= 0x01;	//Set global bit to indicate forward.
			c17 &= 0xFD;	//Set global bit to not indicate reverse.
		}
	}
	else if ((s23 >= 0) && (s23 < 0xF0))	//See if s23 is in rev range
	{					//If so, then proceed with rev.
		if ((c17 | 0xFE) == 0xFE)	//If global indicates present
		{				//direction is not forward, then ...
			outp(0,OCR0); 	//Block forward by shutting down PWM0.
			ptr = inp(PORTB);	//Get present value of port B.
			ptr &= 0xFB;	//Stop forward by setting driver to 0.
			outp(ptr,PORTB);	//Update value of port B.
			ptr = -(volatile unsigned char)s23;//Assign movement to ptr.
			outp(ptr, OCR2);	//Assign PWM to new movement value.
			ptr = inp(PORTB);	//Get present state of port B.
			ptr |= 0x20;	//Indicate that the direction is forward.
			outp(ptr,PORTB);	//Update the value of the port.
			c17 |= 0x02;	//Set global bit to indicate reverse.
			c17 &= 0xFE;	//Set global bit to not indicate reverse.
		}
	}
	return(0);
}