app/ticker.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
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88

#include "project.h"


static volatile uint32_t delay_ms_count;
volatile uint32_t ticks;
static uint32_t scale = 7;

void
delay_us (uint32_t d)
{
  d *= scale;
  while (d--)
    {
      __asm__ ("nop");
    }
}


void
sys_tick_handler (void)
{
  uint8_t d;

  if (delay_ms_count)
    delay_ms_count--;

  ticks++;

  while (!ring_read_byte (&rx1_ring, &d))
    kvm_recv (d);

  while (!ring_read_byte (&rx2_ring, &d))
    kvm_recv (d);

  led_tick ();

  usb_tick();
}


void
delay_ms (uint32_t d)
{
  delay_ms_count = d;
  while (delay_ms_count);
}

int
timed_out (uint32_t then, unsigned int ms)
{
  then = ticks - then;

  if (then > ms)
    return 1;
  return 0;
}


void
ticker_init (void)
{
  uint32_t v, w;

  /*Start periodic timer */

  systick_set_clocksource (STK_CSR_CLKSOURCE_AHB_DIV8);
  /* 48MHz / 8 = > 6Mhz */
  systick_set_reload (6000);
  /* 6MHz / 6000 => 1kHz */
  systick_interrupt_enable ();
  systick_counter_enable ();


  /*Calibrate the delay loop */
  do
    {
      scale--;
      v = ticks;
      while (v == ticks);
      delay_us (1000);
      w = ticks;
      v++;
      w -= v;
    }
  while (w);


}