some problem in the rpm code for gettting the dutycycle in the OCR

[sangeetha sangu]

hi, can any one please help me with this code we are not able to sortout were the overflow is happening we have tried a lot to sort it out.
/*******************************************************
This program was created by the
CodeWizardAVR V2.60 Evaluation
Automatic Program Generator
© Copyright 1998-2012 Pavel Haiduc, HP InfoTech s.r.l.
http://www.hpinfotech.com

Project :
Version :
Date : 4/23/2013
Author :
Company :
Comments:


Chip type : ATmega8L
Program type : Application
AVR Core Clock frequency: 1.000000 MHz
Memory model : Small
External RAM size : 0
Data Stack size : 256
*******************************************************/

#include <mega8.h>
#define P_GAIN
#define I_GAIN
#define D_GAIN
#define dt
#define tim_freq 1000000
#define teeth 12


// Declare your global variables here
int set_rpm=0,previous_error=0;
int error, feedback_rpm,output;
int D_error=0,I_error=0;
int j,rpm;
unsigned int c_rpm,p_rpm=0;
unsigned long int count;

// Timer1 overflow interrupt service routine
interrupt [TIM1_OVF] void timer1_ovf_isr(void)
{
// Place your code here
j++;
return;
}

// Timer1 input capture interrupt service routine
interrupt [TIM1_CAPT] void timer1_capt_isr(void)
{
// Place your code here
c_rpm= ICR1;
if(j)
{
count=(int)((65535 - p_rpm)+((j-1)*65535)+c_rpm);
}
else
{
count=(c_rpm - p_rpm);
}
rpm = (60*tim_freq);
rpm = (rpm/(teeth * count));
feedback_rpm=rpm;
j=0;
p_rpm=c_rpm;

}

// Timer2 overflow interrupt service routine
interrupt [TIM2_OVF] void timer2_ovf_isr(void)
{
// Place your code here
PORTC = 0x0ff;
}

// Timer2 output compare interrupt service routine
interrupt [TIM2_COMP] void timer2_comp_isr(void)
{
// Place your code here
OCR2=(5*count/1000)*255;
PORTC =0x00;
}

void main(void)
{
// Declare your local variables here

// Input/Output Ports initialization
// Port B initialization
// Function: Bit7=In Bit6=In Bit5=In Bit4=In Bit3=Out Bit2=In Bit1=In Bit0=In
DDRB=(0<<DDB7) | (0<<DDB6) | (0<<DDB5) | (0<<DDB4) | (1<<DDB3) | (0<<DDB2) | (0<<DDB1) | (0<<DDB0);
// State: Bit7=T Bit6=T Bit5=T Bit4=T Bit3=0 Bit2=T Bit1=T Bit0=T
PORTB=(0<<PORTB7) | (0<<PORTB6) | (0<<PORTB5) | (0<<PORTB4) | (0<<PORTB3) | (0<<PORTB2) | (0<<PORTB1) | (0<<PORTB0);

// Port C initialization
// Function: Bit6=In Bit5=In Bit4=In Bit3=In Bit2=In Bit1=In Bit0=In
DDRC=(0<<DDC6) | (0<<DDC5) | (0<<DDC4) | (0<<DDC3) | (0<<DDC2) | (0<<DDC1) | (0<<DDC0);
// State: Bit6=T Bit5=T Bit4=T Bit3=T Bit2=T Bit1=T Bit0=T
PORTC=(0<<PORTC6) | (0<<PORTC5) | (0<<PORTC4) | (0<<PORTC3) | (0<<PORTC2) | (0<<PORTC1) | (0<<PORTC0);

// Port D initialization
// Function: Bit7=In Bit6=In Bit5=In Bit4=In Bit3=In Bit2=In Bit1=In Bit0=In
DDRD=(0<<DDD7) | (0<<DDD6) | (0<<DDD5) | (0<<DDD4) | (0<<DDD3) | (0<<DDD2) | (0<<DDD1) | (0<<DDD0);
// State: Bit7=T Bit6=T Bit5=T Bit4=T Bit3=T Bit2=T Bit1=T Bit0=T
PORTD=(0<<PORTD7) | (0<<PORTD6) | (0<<PORTD5) | (0<<PORTD4) | (0<<PORTD3) | (0<<PORTD2) | (0<<PORTD1) | (0<<PORTD0);

// Timer/Counter 0 initialization
// Clock source: System Clock
// Clock value: Timer 0 Stopped
TCCR0=(0<<CS02) | (0<<CS01) | (0<<CS00);
TCNT0=0x00;

// Timer/Counter 1 initialization
// Clock source: System Clock
// Clock value: 1000.000 kHz
// Mode: Normal top=0xFFFF
// OC1A output: Disconnected
// OC1B output: Disconnected
// Noise Canceler: Off
// Input Capture on Rising Edge
// Timer Period: 65.536 ms
// Timer1 Overflow Interrupt: On
// Input Capture Interrupt: On
// Compare A Match Interrupt: Off
// Compare B Match Interrupt: Off
TCCR1A=(0<<COM1A1) | (0<<COM1A0) | (0<<COM1B1) | (0<<COM1B0) | (0<<WGM11) | (0<<WGM10);
TCCR1B=(0<<ICNC1) | (1<<ICES1) | (0<<WGM13) | (0<<WGM12) | (0<<CS12) | (0<<CS11) | (1<<CS10);
TCNT1H=0x00;
TCNT1L=0x00;
ICR1H=0x00;
ICR1L=0x00;
OCR1AH=0x00;
OCR1AL=0x00;
OCR1BH=0x00;
OCR1BL=0x00;

// Timer/Counter 2 initialization
// Clock source: System Clock
// Clock value: 1000.000 kHz
// Mode: Fast PWM top=0xFF
// OC2 output: Non-Inverted PWM
// Timer Period: 0.256 ms
// Output Pulse(s):
// OC2 Period: 0.256 ms Width: 0 us
ASSR=0<<AS2;
TCCR2=(1<<PWM2) | (1<<COM21) | (0<<COM20) | (1<<CTC2) | (0<<CS22) | (0<<CS21) | (1<<CS20);
TCNT2=0x00;
OCR2=0x00;

// Timer(s)/Counter(s) Interrupt(s) initialization
TIMSK=(1<<OCIE2) | (1<<TOIE2) | (1<<TICIE1) | (0<<OCIE1A) | (0<<OCIE1B) | (1<<TOIE1) | (0<<TOIE0);

// External Interrupt(s) initialization
// INT0: Off
// INT1: Off
MCUCR=(0<<ISC11) | (0<<ISC10) | (0<<ISC01) | (0<<ISC00);

// USART initialization
// USART disabled
UCSRB=(0<<RXCIE) | (0<<TXCIE) | (0<<UDRIE) | (0<<RXEN) | (0<<TXEN) | (0<<UCSZ2) | (0<<RXB8) | (0<<TXB8);

// Analog Comparator initialization
// Analog Comparator: Off
ACSR=(1<<ACD) | (0<<ACBG) | (0<<ACO) | (0<<ACI) | (0<<ACIE) | (0<<ACIC) | (0<<ACIS1) | (0<<ACIS0);
SFIOR=(0<<ACME);

// ADC initialization
// ADC disabled
ADCSRA=(0<<ADEN) | (0<<ADSC) | (0<<ADFR) | (0<<ADIF) | (0<<ADIE) | (0<<ADPS2) | (0<<ADPS1) | (0<<ADPS0);

// SPI initialization
// SPI disabled
SPCR=(0<<SPIE) | (0<<SPE) | (0<<DORD) | (0<<MSTR) | (0<<CPOL) | (0<<CPHA) | (0<<SPR1) | (0<<SPR0);

// TWI initialization
// TWI disabled
TWCR=(0<<TWEA) | (0<<TWSTA) | (0<<TWSTO) | (0<<TWEN) | (0<<TWIE);

// Global enable interrupts
#asm("sei")
set_rpm =100;
previous_error=set_rpm-feedback_rpm;
while (1)
{
// Place your code here
error = (set_rpm - feedback_rpm);
D_error = (error - previous_error)/dt;
I_error +=(error)*dt;
output = (P_GAIN * error)+(I_GAIN * I_error)+(D_GAIN *D_error);
previous_error = error;


}
}

 

[BradtheRad]

You declare some variables as unsigned. I don't know for certain if this is the cause of your overflow, but my experience is that it is less confusing when I stick with signed variables.

This means that when I have a one-byte variable ranging between zero and +127, and one day I realize its value could possibly go over 127, then I bump it up to a two byte variable.

The same if its value could ever go negative, accidentally or deliberately. I forget whether that causes an error, but it ought to.

From what I understand, the calculating routines handle signed variables in a more straightforward manner. On the other hand, mixing signed and unsigned may conceivably have a bug somewhere.