Citat:
shadow-bg:
Kako meriti duzinu impulsa sa PIC-om?
Koristi pic sa CCP modulom. On je idealan za merenje duzene nekog impulsa. Pogledaj datasheet za ccp imas tamo primer.
evo ga neki deo koda za P16F690 koji meri duzinu nekog impulsa ... kod je sto godina star ali bi trebalo da je jasan
Code:
#define interrupt_on() PIR1 = 0x00; PIE1 = 0x04; INTCON = 0xC0
#define interrupt_off() INTCON = 0x00;
unsigned char pokupio;
unsigned char skupljaj;
unsigned int T1; //timer1 overflow
unsigned long T1_old;
unsigned long T1_new;
unsigned char bafer[25];
#define vd() Vdelay_ms(100)
#define blink() Vdelay_ms(100)
void Init(){
//init ports
ADCON0 = 0;
ADCON1 = 0;
ANSEL = 0;
ANSELH = 0;
TRISC = 1<<5; //RC5 is CCP1
PORTC = 0;
TRISB = 0;
PORTB = 0;
TRISA = 0;
PORTA = 0;
//init variables
pokupio=0;
skupljaj=0;
T1 = 0;
//init interrupts, timers
CCP1CON = 0x05; // 0000 0101 Capture mode every rising edge
T1CON = 0x01; // 00 00 (prescaler 1:1) 000 1(turn on the timer1)
T1_old = 0;
T1_new = 0;
}
void main(){
unsigned long daljina;
Init();
daljina = 0;
pokupio = 0;
while(1){
interrupt_off();
Vdelay_ms(200);
skupljaj = 1;
T1 = 0;
T1_old = (TMR1H << 8) | TMR1L;
T1_new = 0;
ping();
interrupt_on();
prikazi(daljina); // ovo traje neko vreme
interrupt_off();
if (pokupio){
pokupio = 0;
// 8MHz crystal -> 2000000 ticks in second
// speed of air at 20deg 340m/s
// noTicks * 340 / 2000000 = double distance in m
// (noTicks * 340 / 2000000)*100/2 = distance in cm
// distance in cm = noTicks * 34 / 4000 = noTicks *17/2000
if (T1_new < T1_old) continue;
daljina = T1_new - T1_old;
daljina *= 17;
daljina /=2000;
} else {
daljina = 32000;
//nothing();
continue;
}
}
}
void interrupt(){
if (PIR1 & (1<<TMR1IF)) { // timer1 overfow
PIR1 &= ~(1<<TMR1IF); // clear timer1 interrupt flag
T1++;
}
if (PIR1 & (1<<CCP1IF)) { // we captured the echo
PIR1 &= ~(1<<CCP1IF);
if (skupljaj){ // if we were waiting for the echo
skupljaj = 0; //we do not expect another one
pokupio = 1;
T1_new = (T1 << 16) | (CCPR1H << 8) | CCPR1L; // on capture TMR1x is copied into CCPR1x
}
}
}
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Merenje duzine impulsa na PIC?