问i.MX 8M EVK :如何计算1ms定时器的频率值？

EN

/*
 * Copyright (c) 2016, Freescale Semiconductor, Inc.
 * Copyright 2016-2017 NXP
 * All rights reserved.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

#include "fsl_debug_console.h"
#include "pin_mux.h"
#include "clock_config.h"
#include "board.h"
#include "fsl_gpt.h"
#include "fsl_gpio.h"

#include "fsl_common.h"
/*******************************************************************************
 * Definitions
 ******************************************************************************/
#define GPT_IRQ_ID  GPT1_IRQn
#define EXAMPLE_GPT GPT1
//#define EXAMPLE_GPT_CLK_FREQ                                                                \
//    (CLOCK_GetPllFreq(kCLOCK_SystemPll1Ctrl) / (CLOCK_GetRootPreDivider(kCLOCK_RootGpt1)) / \
//     (CLOCK_GetRootPostDivider(kCLOCK_RootGpt1)) / 2) /* SYSTEM PLL1 DIV2 */
#define EXAMPLE_GPT_CLK_FREQ    100000
#define EXAMPLE_GPT_IRQHandler GPT1_IRQHandler

#define EXAMPLE_LED_GPIO     GPIO3
#define EXAMPLE_LED_GPIO_PIN 23U

/*******************************************************************************
 * Prototypes
 ******************************************************************************/

/*******************************************************************************
 * Variables
 ******************************************************************************/

volatile bool gptIsrFlag = false;
/* The PIN status */
volatile bool g_pinSet = false;

/*******************************************************************************
 * Code
 ******************************************************************************/
void EXAMPLE_GPT_IRQHandler(void)
{
    /* Clear interrupt flag.*/
    GPT_ClearStatusFlags(EXAMPLE_GPT, kGPT_OutputCompare1Flag);

    gptIsrFlag = true;
/* Add for ARM errata 838869, affects Cortex-M4, Cortex-M4F, Cortex-M7, Cortex-M7F Store immediate overlapping
  exception return operation might vector to incorrect interrupt */
#if defined __CORTEX_M && (__CORTEX_M == 4U || __CORTEX_M == 7U)
    __DSB();
#endif
}

/*!
 * @brief Main function
 */
int main(void)
{
    uint32_t gptFreq;
    gpt_config_t gptConfig;

    /* Define the init structure for the output LED pin*/
    gpio_pin_config_t led_config = {kGPIO_DigitalOutput, 0, kGPIO_NoIntmode};

    /* Board pin, clock, debug console init */
    /* Board specific RDC settings */
    BOARD_RdcInit();

    BOARD_InitBootPins();
    BOARD_BootClockRUN();
    BOARD_InitDebugConsole();
    BOARD_InitMemory();

    CLOCK_SetRootMux(kCLOCK_RootGpt1, kCLOCK_GptRootmuxSysPll1Div2); /* Set GPT1 source to SYSTEM PLL1 DIV2 400MHZ */
    CLOCK_SetRootDivider(kCLOCK_RootGpt1, 1U, 4U);                   /* Set root clock to 400MHZ / 4 = 100MHZ */

    GPT_GetDefaultConfig(&gptConfig);

    /* Initialize GPT module */
    GPT_Init(EXAMPLE_GPT, &gptConfig);

    /* Divide GPT clock source frequency by 3 inside GPT module */
    GPT_SetClockDivider(EXAMPLE_GPT, 1);

    /* Get GPT clock frequency */
    gptFreq = EXAMPLE_GPT_CLK_FREQ;

    /* GPT frequency is divided by 3 inside module */
    gptFreq /= 1;

    /* Set both GPT modules to 1 second duration */
    GPT_SetOutputCompareValue(EXAMPLE_GPT, kGPT_OutputCompare_Channel1, gptFreq);

    /* Enable GPT Output Compare1 interrupt */
    GPT_EnableInterrupts(EXAMPLE_GPT, kGPT_OutputCompare1InterruptEnable);

    /* Enable at the Interrupt */
    EnableIRQ(GPT_IRQ_ID);

    PRINTF("\r\nPress any key to start the example");
    GETCHAR();

    /* Init output LED GPIO. */
    GPIO_PinInit(EXAMPLE_LED_GPIO, EXAMPLE_LED_GPIO_PIN, &led_config);

    /* Start Timer */
    PRINTF("\r\nStarting GPT timer ...");
    GPT_StartTimer(EXAMPLE_GPT);

    while (true)
    {
        /* Check whether occur interupt and toggle LED */
        if (true == gptIsrFlag)
        {
            PRINTF("\r\n GPT interrupt is occurred !");
            gptIsrFlag = false;
            if (g_pinSet)
            {
                GPIO_PinWrite(EXAMPLE_LED_GPIO, EXAMPLE_LED_GPIO_PIN, 0U);
                g_pinSet = false;
            }
            else
            {
                GPIO_PinWrite(EXAMPLE_LED_GPIO, EXAMPLE_LED_GPIO_PIN, 1U);
                g_pinSet = true;
            }
        }
        else
        {
            __WFI();
        }
    }
}