Nano100的定时器写延时函数

1万 · 2017-5-4 17:42



/******************************************************************************

 * [url=home.php?mod=space&uid=288409]@file[/url]     main.c

 * [url=home.php?mod=space&uid=895143]@version[/url]  V1.00

 * $Revision: 3 $

 * $Date: 14/09/11 7:17p $

 * [url=home.php?mod=space&uid=247401]@brief[/url]    Demonstrate the usage of TIMER_Delay() API to generate a 1 second delay

 *

 * @note

 * Copyright (C) 2013 Nuvoton Technology Corp. All rights reserved.

*****************************************************************************/

#include <stdio.h>

#include "Nano100Series.h"



void SYS_Init(void)

{

    /*---------------------------------------------------------------------------------------------------------*/

    /* Init System Clock                                                                                       */

    /*---------------------------------------------------------------------------------------------------------*/

    /* Unlock protected registers */

    SYS_UnlockReg();



    /* Enable External XTAL (4~24 MHz) */

    CLK_EnableXtalRC(CLK_PWRCTL_HXT_EN_Msk);



    /* Waiting for 12MHz clock ready */

    CLK_WaitClockReady( CLK_CLKSTATUS_HXT_STB_Msk);



    /* Switch HCLK clock source to HXT */

    CLK_SetHCLK(CLK_CLKSEL0_HCLK_S_HXT,CLK_HCLK_CLK_DIVIDER(1));



    /* Enable IP clock */

    CLK_EnableModuleClock(UART0_MODULE);

    CLK_EnableModuleClock(TMR0_MODULE);





    /* Select IP clock source */

    CLK_SetModuleClock(UART0_MODULE, CLK_CLKSEL1_UART_S_HXT, CLK_UART_CLK_DIVIDER(1));

    CLK_SetModuleClock(TMR0_MODULE, CLK_CLKSEL1_TMR0_S_HXT, 0);



    /* Update System Core Clock */

    /* User can use SystemCoreClockUpdate() to calculate SystemCoreClock. */

    SystemCoreClockUpdate();





    /*---------------------------------------------------------------------------------------------------------*/

    /* Init I/O Multi-function                                                                                 */

    /*---------------------------------------------------------------------------------------------------------*/

    /* Set GPB multi-function pins for UART0 RXD and TXD */

    SYS->PB_L_MFP &= ~(SYS_PB_L_MFP_PB0_MFP_Msk | SYS_PB_L_MFP_PB1_MFP_Msk);

    SYS->PB_L_MFP |= (SYS_PB_L_MFP_PB1_MFP_UART0_TX | SYS_PB_L_MFP_PB0_MFP_UART0_RX);





    /* Lock protected registers */

    SYS_LockReg();

}



int main(void)

{

    /* Init System, IP clock and multi-function I/O

       In the end of SYS_Init() will issue SYS_LockReg()

       to lock protected register. If user want to write

       protected register, please issue SYS_UnlockReg()

       to unlock protected register if necessary */

    SYS_Init();



    /* Init UART to 115200-8n1 for print message */

    UART_Open(UART0, 115200);



    printf("\nThis sample code use timer to create a small delay \n");

    while(1) {

        printf("Delay 1 second\n");

        TIMER_Delay(TIMER0, 1000000);

    }



}



/*** (C) COPYRIGHT 2013 Nuvoton Technology Corp. ***/

1万 · 2017-5-4 17:44

void TIMER_Delay(TIMER_T *timer, uint32_t u32Usec);
这个是定时器延时函数的原型

1万 · 2017-5-4 17:45

复制

/**

  * @brief This API is used to create a delay loop for u32usec micro seconds

  * @param[in] timer The base address of Timer module

  * @param[in] u32Usec Delay period in micro seconds with 10 usec every step. Valid values are between 10~1000000 (10 micro second ~ 1 second)

  * [url=home.php?mod=space&uid=266161]@return[/url] None

  * @note This API overwrites the register setting of the timer used to count the delay time.

  * @note This API use polling mode. So there is no need to enable interrupt for the timer module used to generate delay

  */

void TIMER_Delay(TIMER_T *timer, uint32_t u32Usec)

{

    uint32_t u32Clk = TIMER_GetModuleClock(timer);

    uint32_t u32Prescale = 0, delay = SystemCoreClock / u32Clk;

    long long u64Cmpr;



    // Clear current timer configuration

    timer->CTL = 0;



    if(u32Clk == 10000) {         // min delay is 100us if timer clock source is LIRC 10k

        u32Usec = ((u32Usec + 99) / 100) * 100;

    } else {    // 10 usec every step

        u32Usec = ((u32Usec + 9) / 10) * 10;

    }



    if(u32Clk >= 0x2000000) {

        u32Prescale = 3;    // real prescaler value is 4

        u32Clk >>= 2;

    } else if(u32Clk >= 0x1000000) {

        u32Prescale = 1;    // real prescaler value is 2

        u32Clk >>= 1;

    }



    // u32Usec * u32Clk might overflow if using uint32_t

    u64Cmpr = ((long long)u32Usec * (long long)u32Clk) / (long long)1000000;



    timer->CMPR = (uint32_t)u64Cmpr;

    timer->PRECNT = u32Prescale;

    timer->CTL = TIMER_CTL_TMR_EN_Msk; // one shot mode



    // When system clock is faster than timer clock, it is possible timer active bit cannot set in time while we check it.

    // And the while loop below return immediately, so put a tiny delay here allowing timer start counting and raise active flag.

    for(; delay > 0; delay--) {

        __NOP();

    }



    while(timer->CTL & TIMER_CTL_TMR_ACT_Msk);



}

这个是定时器延时函数的实现
实现的过程是复杂的，我们是不是该考虑这个实现过程消耗掉的时间呢？

只看该作者 · 2017-5-4 23:14

通过查询定时器做到延时的效果

1万 · 2017-5-5 14:40

关于那个实现过程，感觉好复杂，没看懂。

只看该作者 · 2017-5-5 16:21

看了一下，基本上那个系统初始化代码都是可以拿来主义的。

1万 · 2017-5-6 20:52

如果跑系统，那么系统是如何管理这些中断和定时器的？

只看该作者 · 2017-5-7 16:17

u32Usec Delay period in micro seconds with 10 usec every step. Valid values are between 10~1000000 (10 micro second ~ 1 second)
这个是延时的范围，还是很大呢，那个最小的是10，可能就是考虑到了实现部分的其他代码。