92 lines
1.4 KiB
C
92 lines
1.4 KiB
C
#include "stm32f4xx.h"
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#include "core_delay.h"
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#include "rtthread.h"
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#include <rthw.h>
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#define DWT_CR *(__IO uint32_t *)0xE0001000
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#define DWT_CYCCNT *(__IO uint32_t *)0xE0001004
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#define DEM_CR *(__IO uint32_t *)0xE000EDFC
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#define DEM_CR_TRCENA (1 << 24)
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#define DWT_CR_CYCCNTENA (1 << 0)
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//获取系统主频
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static uint32_t get_sys_clocks_freq (void)
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{
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RCC_ClocksTypeDef t={0};
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RCC_GetClocksFreq (&t);
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return t.SYSCLK_Frequency;
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}
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int delay_init(void)
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{
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DEM_CR |= (uint32_t)DEM_CR_TRCENA;
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DWT_CYCCNT = (uint32_t)0u;
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DWT_CR |= (uint32_t)DWT_CR_CYCCNTENA;
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return 0;
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}
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static uint32_t delay_get_cnt(void)
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{
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return ((uint32_t)DWT_CYCCNT);
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}
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static uint32_t delay_get_tick(void)
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{
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return ((uint32_t)DWT_CYCCNT*1000/get_sys_clocks_freq());
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}
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// 低于1ms的精确延时
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void delay_us(uint32_t us)
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{
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uint32_t ticks;
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uint32_t told, tnow, tcnt=0;
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/* 需要的节拍数 */
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ticks = us * (get_sys_clocks_freq() / 1000000);
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tcnt = 0;
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told = (uint32_t)delay_get_cnt();
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while (1)
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{
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tnow = (uint32_t)delay_get_cnt();
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if (tnow != told)
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{
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/* 32 位计数器是递增计数器 */
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if (tnow > told)
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{
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tcnt += tnow - told;
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}
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/* 重新装载 */
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else
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{
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tcnt += UINT32_MAX - told + tnow;
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}
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told = tnow;
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/*时间超过/等于要延迟的时间,则退出 */
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if (tcnt >= ticks)break;
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}
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}
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}
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// 实现rt_thread 的us级延时
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void rt_hw_us_delay(rt_uint32_t us)
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{
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delay_us(us);
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}
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