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comparison delay.c @ 40:a38003b97de6

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Use debug cycle counter to handle delays.
author Daniel O'Connor <darius@dons.net.au>
date Mon, 01 Apr 2013 20:06:03 +1030
parents 891841f5f785
children cecb0506f4b8
comparison
equal deleted inserted replaced
39:969bb070b181 40:a38003b97de6
1 #include <assert.h>
1 #include <stdint.h> 2 #include <stdint.h>
2 #include "stm32f10x.h" 3 #include "stm32f10x.h"
3 #include "delay.h" 4 #include "delay.h"
4 5
5 /* Sleep for nCount usec 6 /* Sleep for nCount usec
6 * TDS1012 on 2.5usec/div shows...
7 * 30usec = 29.60usec
8 * 60usec = 59.20usec
9 *
10 * XXX: not sure disable IRQ stuff is working as I see occasional (small) extra delays
11 */ 7 */
12 void 8 void
13 delay(uint32_t nCount) { 9 delay(uint32_t nCount) {
10 uint32_t dly, cnt, clk_per_usec, max_dly;
11 volatile uint32_t *DWT_CYCCNT = (uint32_t *)0xe0001004;
12
14 __disable_irq(); 13 __disable_irq();
15 for(; nCount != 0; nCount--) { 14
16 #ifdef SYSCLK_FREQ_72MHz 15 #ifdef SYSCLK_FREQ_72MHz
17 __asm__("nop"); 16 clk_per_usec = 72;
18 __asm__("nop"); 17 max_dly = (1<<31) / clk_per_usec; /* Really half the maximum (still ~30 seconds at 72MHz) */
19 __asm__("nop");
20 __asm__("nop");
21 __asm__("nop");
22 __asm__("nop");
23 __asm__("nop");
24 __asm__("nop");
25
26 __asm__("nop");
27 __asm__("nop");
28 __asm__("nop");
29 __asm__("nop");
30 __asm__("nop");
31 __asm__("nop");
32 __asm__("nop");
33 __asm__("nop");
34
35 __asm__("nop");
36 __asm__("nop");
37 __asm__("nop");
38 __asm__("nop");
39 __asm__("nop");
40 __asm__("nop");
41 __asm__("nop");
42 __asm__("nop");
43
44 __asm__("nop");
45 __asm__("nop");
46 __asm__("nop");
47 __asm__("nop");
48 __asm__("nop");
49 __asm__("nop");
50 __asm__("nop");
51
52 __asm__("nop");
53 __asm__("nop");
54 __asm__("nop");
55 __asm__("nop");
56 __asm__("nop");
57 __asm__("nop");
58 __asm__("nop");
59 __asm__("nop");
60
61 __asm__("nop");
62 __asm__("nop");
63 __asm__("nop");
64 __asm__("nop");
65 __asm__("nop");
66 __asm__("nop");
67 __asm__("nop");
68
69 __asm__("nop");
70 __asm__("nop");
71 __asm__("nop");
72 __asm__("nop");
73 __asm__("nop");
74 __asm__("nop");
75 __asm__("nop");
76 __asm__("nop");
77 #else 18 #else
78 #error Unknown clock frequency 19 #error "Unknown clock frequency"
79 #endif 20 #endif
80 } 21 assert(nCount < max_dly);
22
23 cnt = *DWT_CYCCNT; /* Get current cycle count */
24 dly = nCount * clk_per_usec;
25 dly += cnt; /* Compute cycle count to stop at */
26 if (dly < cnt)
27 /* Stop count wrapped, wait until the counter wraps around */
28 while (*DWT_CYCCNT > cnt)
29 ;
30 /* Wait until we get to the stop count */
31 while (*DWT_CYCCNT < dly)
32 ;
33
81 __enable_irq(); 34 __enable_irq();
82 } 35 }
83 36