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Problems with PWM measuring using ICP in ATMega328

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feluma

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Hello,

I'm new to PWM techniques and I can't find a simple code to compare mine to get a PW mesure using my ATMega328.

The problem is that right now I get measures, but they are not consistent, they present a very wide range of values for the same input signal; I don't know if this is because some asyncronous problem wrong set of registers or other thing.

If somebady could help me would be nice.

Code:
#include <avr\io.h>
#include <avr\interrupt.h>
#include <stdio.h>
#include <string.h>
#define F_CPU 8000000
#include <util/delay.h>



//Asynchronous serial communication

#define BAUD 9600
#define MYUBRR ((F_CPU/BAUD/16)-1)



//ICP measuring

#define ICP PINB0

//define ovrflow counter
uint16_t ov_counter;

//define times for start and end of signal
uint16_t rising, falling;

//define overall counts
uint32_t counts;


//overflow counter interrupts service routine
ISR(TIMER1_OVF_vect){
  ov_counter++;
}

//Timer1 capture interrupt service subroutine
ISR(TIMER1_CAPT_vect){

	// This subroutine checks was it start of pulse (rising edge) 
    // or was it end (fallingedge) and performs required operations

	if (ICP){ //if high level

            //save start time

            rising=ICR1;

            //set to trigger on falling edge

            TCCR1B=TCCR1B&0xBF;

            //reset overflow counter

            ov_counter=0;

	}
	else{

            //save falling time

            falling=ICR1;

            //rising edge triggers next

            TCCR1B=TCCR1B|0x40;

            counts=(uint32_t)falling-(uint32_t)rising+(uint32_t)ov_counter;

			//you can convert coutns to seconds and send to LCD
			printf("%lu\n", (unsigned long)counts); //Values variates from 800 to 62000 for the same input signal.
            }
	_delay_ms(100);
}



//Define functions
//======================

void ioinit(void); // Initializes IO
static int uart_putchar(char c, FILE *stream);
uint8_t uart_getchar(void);

static FILE mystdout = FDEV_SETUP_STREAM(uart_putchar, NULL, _FDEV_SETUP_WRITE);


int main(void) {

	ioinit(); //Setup IO pins and defaults

	//PWM
	TIMSK1=0x24; //Enable overflow and input capture interrupts
	TCCR1B=0xC1; //Noise canceller, without prescaler, rising edge
	sei(); //Enable interrupts

    while(1) {  // Loop forever timer does the job
	}


return(0);
}




void ioinit (void)
{
    //1 = output, 0 = input
    DDRB = 0b11111110; //PORTB (yP on PB0 / Accelerometer)
    DDRC = 0b11111111; //
    DDRD = 0b11111110; //PORTD (RX on PD0)

    UBRR0H = 0b00000000;
    UBRR0L = 0b00110011;

	UCSR0A = 0b00100000;
	UCSR0B = 0b00011000;
	UCSR0C = 0b00110110;

    
    stdout = &mystdout; //Required for printf init



	
}


static int uart_putchar(char c, FILE *stream)
{
    if (c == '\n') uart_putchar('\r', stream);
  
    loop_until_bit_is_set(UCSR0A, UDRE0);
    UDR0 = c;
    
    return 0;
}

uint8_t uart_getchar(void)
{
    while( !(UCSR0A & (1<<RXC0)) );
    return(UDR0);
}
 

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