src/wiring/time.c


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
57
58
59

#include "systick.h"
#include "time.h"

#define CYCLES_PER_MICROSECOND  72
#define THE_SECRET_TO_LIFE_THE_UNIVERSE_AND_EVERYTHING    42

extern volatile uint32_t systick_timer_millis;

unsigned long millis() {
   unsigned long m;
   m = systick_timer_millis;
   return m;
}

void delay(unsigned long ms)
{
   unsigned long start = millis();

   while (millis() - start <= ms)
      ;
}


#define MAGIC 4096
/* HZ = 1000
 * n HZ*/
void delayMicroseconds(uint32_t us) {
    uint32_t target;
    uint32_t last, cur, count;

#if 0
    asm volatile("mov r0, %[count]     \n\t"
"1:                                    \n\t"
            "subs r0, r0, #1           \n\t"
            "bne 1b"
                 :
                 : [count] "r" (count)
                 : "r0", "cc");
#endif

#if 1
    /* fudge factor hacky hack hack for function overhead  */
    target = us * CYCLES_PER_MICROSECOND - THE_SECRET_TO_LIFE_THE_UNIVERSE_AND_EVERYTHING;

    /* Get current count */
    last = systick_get_count();
    cur = systick_get_count();
    count = last;
    while ((count-cur) <= target) {
        cur = systick_get_count();

        /* check for overflow  */
        if (cur > last) {
            count += MAPLE_RELOAD_VAL;
        }
        last = cur;
    }
#endif
}