ESPIDF-定时器

概述

ESP32 内置 4 个 64-bit 通用定时器。每个定时器包含一个 16-bit 预分频器和一个 64-bit 可自动重新加载向上／向下计数器。
ESP32 的定时器分为 2 组，每组 2 个。TIMGn_Tx 的 n 代表组别，x 代表定时器编号。

功能描述

16-bit 预分频器

每个定时器都以 APB 时钟（缩写 APB_CLK，频率通常为 80 MHz）作为基础时钟。16-bit 预分频器对 APB 时钟进
行分频，产生时基计数器时钟（TB_clk）。TB_clk 每过一个周期，时基计数器会向上数一或者向下数一。在使用寄存
器 TIMGn_Tx_DIVIDER 配置分频器除数前，必须关闭定时器（清零 TIMGn_Tx_DIVIDER）。定时器使能时配置预分
频器会导致不可预知的结果。预分频器可以对 APB 时钟进行 2 到 65536 的分频。具体来说，TIMGn_Tx_DIVIDER
为 1 或 2 时，时钟分频器是 2；TIMGn_Tx_DIVIDER 为 0 时，时钟分频器是 65536。如 TIMGn_Tx_DIVIDER 为
其他任意值，时钟会被相同数值分频。

64-bit 时基计数器

TIMGn_Tx_INCREASE 置 1 或清零可以将 64-bit 时基计数器分别配置为向上计数或向下计数。同时，64-bit 时基计数器支持自动重新加载和软件即时重新加载，计数器达到软件设定值时会触发报警事件。
TIMGn_Tx_EN 置 1 或清零可以使能或关闭计数。清零后计数器暂停计数，并会在 TIMGn_Tx_ EN 重新置 1 前保持其值不变。清零 TIMGn_Tx _EN 会重新加载计数器并改变计数器的值，但在设置 TIMGn_Tx_EN 前计数不会恢复。

timer_config_t

Data structure with timer’s configuration settings

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typedef struct {
    timer_alarm_t alarm_en;      /*!< Timer alarm enable */
    timer_start_t counter_en;    /*!< Counter enable */
    timer_intr_mode_t intr_type; /*!< Interrupt mode */
    timer_count_dir_t counter_dir; /*!< Counter direction  */
    timer_autoreload_t auto_reload;   /*!< Timer auto-reload */
    uint32_t divider;   /*!< Counter clock divider. The divider's range is from from 2 to 65536. */
#if SOC_TIMER_GROUP_SUPPORT_XTAL
    timer_src_clk_t clk_src;  /*!< Use XTAL as source clock. */
#endif
} timer_config_t;

timer_set_counter_value

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/**
 * @brief Set counter value to hardware timer.
 *
 * @param group_num Timer group, 0 for TIMERG0 or 1 for TIMERG1
 * @param timer_num Timer index, 0 for hw_timer[0] & 1 for hw_timer[1]
 * @param load_val Counter value to write to the hardware timer.
 *
 * @return
 *     - ESP_OK Success
 *     - ESP_ERR_INVALID_ARG Parameter error
 */
esp_err_t timer_set_counter_value(timer_group_t group_num, timer_idx_t timer_num, uint64_t load_val);

timer_set_alarm_value

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/**
 * @brief Set timer alarm value.
 *
 * @param group_num Timer group, 0 for TIMERG0 or 1 for TIMERG1
 * @param timer_num Timer index, 0 for hw_timer[0] & 1 for hw_timer[1]
 * @param alarm_value A 64-bit value to set the alarm value.
 *
 * @return
 *     - ESP_OK Success
 *     - ESP_ERR_INVALID_ARG Parameter error
 */
esp_err_t timer_set_alarm_value(timer_group_t group_num, timer_idx_t timer_num, uint64_t alarm_value);

timer_isr_callback_add

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/**
 * @brief Add ISR handle callback for the corresponding timer.
 *
 * @param group_num Timer group number
 * @param timer_num Timer index of timer group
 * @param isr_handler Interrupt handler function, it is a callback function.
 * @param arg Parameter for handler function
 * @param intr_alloc_flags Flags used to allocate the interrupt. One or multiple (ORred)
 *        ESP_INTR_FLAG_* values. See esp_intr_alloc.h for more info.
 *
 * @note This ISR handler will be called from an ISR.
 *       This ISR handler do not need to handle interrupt status, and should be kept short.
 *       If you want to realize some specific applications or write the whole ISR, you can
 *       call timer_isr_register(...) to register ISR.
 *
 *       The callback should return a bool value to determine whether need to do YIELD at
 *       the end of the ISR.
 *
 *       If the intr_alloc_flags value ESP_INTR_FLAG_IRAM is set,
 *       the handler function must be declared with IRAM_ATTR attribute
 *       and can only call functions in IRAM or ROM. It cannot call other timer APIs.
 *
 * @return
 *     - ESP_OK Success
 *     - ESP_ERR_INVALID_ARG Parameter error
 */
esp_err_t timer_isr_callback_add(timer_group_t group_num, timer_idx_t timer_num, timer_isr_t isr_handler, void *arg, int intr_alloc_flags);