blob: 5830b38d43d36eb0c90b4f76fc2585f08a85f725 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
|
#include <avr/io.h>
#include <avr/interrupt.h>
#include "timer.h"
volatile unsigned char count = 0;
volatile unsigned char hit = 0;
ISR(TIMER0_OVF_vect) {
/* there seems to be no mode of operation which disconnects pin OC0A _and_
* clears the value */
++count;
switch (count) {
case 1:
case 2:
TCNT0 = 0;
break;
/* three overflows happened, next one is a little shorter:
* F_CPU/prescaler-3*256=208.5625 -> 256-208=48 -> zero-based=47 */
case 3:
TCNT0 = 47;
break;
/* one second elapsed */
case 4:
TCNT0 = 0;
count = 0;
++hit;
break;
}
}
bool timerHit () {
bool ret = hit != 0;
hit = 0;
return ret;
}
void timerStart () {
count = 0;
/* reset timer value */
TCNT0 = 0;
/* set normal mode timer0 */
TCCR0A = 0;
/* enable overflow interrupt */
TIMSK0 = (1 << TOIE0);
/* io clock with 1024 prescaler */
TCCR0B = (TCCR0B & ~((1 << CS01)) | (1 << CS02) | (1 << CS00));
}
void timerStop () {
/* zero clock source */
TCCR0B = 0;
}
|
