75 lines
1.5 KiB
C
75 lines
1.5 KiB
C
/*
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* S32K144开发板
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* 感谢原子哥的延时函数
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*/
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#include"cpu.h"
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#include"delay.h"
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#include"uart.h"
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static uint32_t fac_us;
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/*延迟函数致敬原子哥*/
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void SysTick_Init(void) //systick 走 core_clk 48mhz 重装载寄存器 FFFFFF 为16 777 215hz 16.77mhz/48mhz 约等于333毫秒
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{
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S32_SysTick->RVR = 0xFFFFFFul; //重装载寄存器
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S32_SysTick->CVR = 0ul; //当前计数
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S32_SysTick->CSR = 0u; //控制寄存器
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}
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/* Enable SysTick counter and interrupt */
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void SysTick_Enable(void)
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{
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S32_SysTick->CSR = S32_SysTick_CSR_TICKINT(1u) | S32_SysTick_CSR_ENABLE(1);
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}
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/* Disable SysTick */
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void SysTick_Disable(void)
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{
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S32_SysTick->CSR = 0ul;
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}
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static uint32_t fac_us;
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void delay_us(uint32_t nus)
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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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uint32_t reload=S32_SysTick->RVR; //LOAD的值
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ticks=nus*fac_us; //需要的节拍数
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told= S32_SysTick->CVR ; //刚进入时的计数器值
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while(1)
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{
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tnow= S32_SysTick->CVR ;
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if(tnow!=told)
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{
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if(tnow<told)tcnt+=told-tnow; //这里注意一下SYSTICK是一个递减的计数器就可以了.
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else tcnt+=reload-tnow+told;
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told=tnow;
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if(tcnt>=ticks)break; //时间超过/等于要延迟的时间,则退出.
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}
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};
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}
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void delay_ms(uint32_t nms)
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{
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uint32_t i;
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for(i=0;i<nms;i++) delay_us(1000);
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}
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int delay_init(void)
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{
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uint32_t frequency;
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CLOCK_SYS_GetFreq(CORE_CLK, &frequency);
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fac_us = frequency / 1000000;// 得到的频率是mhz 如果想知道1us多少个节拍,需要除 1 000 000
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SysTick_Init(); //systick 走 core_clk 48mhz 重装载寄存器 FFFFFF 为16 777 215hz 16.77mhz/48mhz 0.333秒 约等于333毫秒
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SysTick_Enable();
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return fac_us;
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}
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