roboforum.ru

#include <stdlib.h>
#include <avr/io.h>
#include <avr/interrupt.h>

//global variables: encoder position and direction of rotation
unsigned int enc_pos;
unsigned char enc_dir;

/*
PORTC Pin change interrupt service routine. Decodes the encoder.
For algorithm, see Scott Edwards article from Nuts&Volts V1 Oct. 1995
(righthand bit of old A,B) xor (lefthand bit of new A,B) => dir.
Increment or decrement encoder position accordingly
*/

ISR (PCINT1_vect) {
static unsigned char enc_last=0,enc_now;
enc_now = (PINC & (3<<4))>>4; //read the port pins and shift result to bottom bits
enc_dir = (enc_last & 1)^((enc_now & 2) >> 1);   //determine direction of rotation
if(enc_dir==0) enc_pos++; else enc_pos--;    //update encoder position
enc_last=enc_now;    //remember last state
}

#include "lcd.c"

int main(void)
{
unsigned char buf[8];

enc_pos=0;    //Initialize encoder position

LCDInit();    //Initialize LCD display

DDRC &=~(3<<4); //Port C pins 4 and 5 as input
PCMSK1 |= (3<<PCINT12);    //enable interrupt on pin change, bits 4&5 PORTC
PCICR |= 1<<PCIE1;    //enable interrupt on pin change, PORTC
sei();    //enable global interrupts

while (1){
LCDSendCommand(LCD_Line1);    //display current direction of rotation on line 1
itoa(enc_dir,buf,10);
LCDPrintString(buf);
LCDSendCommand(LCD_Line2);    //display current encoder position on line 2
itoa(enc_pos,buf,10);
LCDPrintString(buf);
}
}