通用定时器

[English]

简介

ESP32-S2 芯片提供两组硬件定时器，每组包含两个通用硬件定时器。

所有通用定时器均基于 16 位预分频器和 64 位可自动重新加载向上/向下计数器。

功能概述

下文介绍了配置和操作定时器的常规步骤：

定时器初始化 - 启动定时器前应设置的参数，以及每个设置提供的具体功能。
定时器控制 - 如何读取定时器的值，如何暂停/启动定时器以及如何改变定时器的操作方式。
警报 - 如何设置和使用警报。
处理中断事务- 如何使用中断提供的回调函数。

定时器初始化

两个 ESP32-S2 定时器组中，每组都有两个定时器，两组共有四个定时器供使用。ESP32-S2 定时器组的类型为 timer_group_t，每组中的个体定时器类型为 timer_idx_t。

首先调用 timer_init() 函数，并将 timer_config_t 结构体传递给此函数，用于定义定时器的工作方式，实现定时器初始化。特别注意以下定时器参数可设置为：

时钟源: 选择时钟源，与时钟分频器一起决定了定时器的分辨率。
分频器: 设置定时器中计数器计数的速度，divider 的设置将用作输入时钟源的除数。默认的时钟源是 APB_CLK (一般是 80 MHz)。更多有关 APB_CLK 时钟频率信息，请查看 ESP32-S2 技术参考手册 > 复位和时钟 [PDF] 章节。
模式: 设置计数器是递增还是递减。可通过从 timer_count_dir_t 中选取一个值，后使用 counter_dir 来选择模式。
计数器使能: 如果计数器已使能，则在调用 timer_init() 后计数器将立即开始递增/递减。您可通过从 timer_start_t 中选取一个值，后使用 counter_en 改变此行为。
报警使能: 可使用 alarm_en 设置。
自动重载: 设置计数器是否应该在定时器警报上使用 auto_reload 自动重载首个计数值，还是继续递增或递减。

要获取定时器设置的当前值，请使用函数 timer_get_config()。

定时器控制

定时器使能后便开始计数。要使能定时器，可首先设置 counter_en 为 true，然后调用函数 timer_init()，或者直接调用函数 timer_start()。您可通过调用函数 timer_set_counter_value() 来指定定时器的首个计数值。要检查定时器的当前值，调用函数 timer_get_counter_value() 或 timer_get_counter_time_sec()。

可通过调用函数 timer_pause() 随时暂停定时器。要再次启动它，调用函数 timer_start()。

要重新配置定时器，可调用函数 timer_init()，该函数详细介绍见定时器初始化。

除此之外，还可通过使用专有函数更改个别设置来重新配置定时器：

设置	专有函数	描述
分频器	`timer_set_divider()`	更改计数频率。为避免发生不可预测情况，更改分频器时应暂停定时器。如果定时器正在运行，则使用 `timer_set_divider()` 将其暂停并更改设置，然后重启定时器。
模式	`timer_set_counter_mode()`	设置计数器应递增还是递减
自动重载	`timer_set_auto_reload()`	设置是否应在定时器警报上重载首个计数值

警报

要设置警报，先调用函数 timer_set_alarm_value()，然后使用 timer_set_alarm() 使能警报。当调用函数 timer_init() 时，也可以在定时器初始化阶段使能警报。

警报已使能且定时器达到警报值后，根据配置，可能会出现以下两种行为：

如果先前已配置，此时将触发中断。有关如何配置中断，请参见处理中断事务。

如 auto_reload 已使能，定时器的计数器将重新加载，从先前配置好的值开始再次计数。应使用函数 timer_set_counter_value() 预先设置该值。

备注

如果已设置警报值且定时器已超过该值，则将立即触发警报。
一旦触发后，警报将自动关闭，需要重新使能以再次触发。

要检查某特定的警报值，调用函数 timer_get_alarm_value()。

处理中断事务

调用 timer_isr_callback_add() 函数可以给某个定时器注册一个中断回调函数，顾名思义，该函数会在中断上下文中被执行，因此用户不能在回调函数中调用任何会阻塞 CPU 的 API。相较于从头编写中断处理程序，使用中断回调函数的好处是，用户无需检测和处理中断的状态位，这些操作会由驱动中默认的中断处理程序替我们完成。

有关如何使用中断回调函数，请参考如下应用示例。

应用示例

64 位通用硬件定时器示例：peripherals/timer_group。

API 参考

Header File

components/driver/include/driver/timer.h

Functions

esp_err_t timer_get_counter_value(timer_group_t group_num, timer_idx_t timer_num, uint64_t *timer_val)

Read the counter value of hardware timer.

参数

group_num – Timer group, 0 for TIMERG0 or 1 for TIMERG1
timer_num – Timer index, 0 for hw_timer[0] & 1 for hw_timer[1]
timer_val – Pointer to accept timer counter value.

返回

ESP_OK Success
ESP_ERR_INVALID_ARG Parameter error

esp_err_t timer_get_counter_time_sec(timer_group_t group_num, timer_idx_t timer_num, double *time)

Read the counter value of hardware timer, in unit of a given scale.

参数

group_num – Timer group, 0 for TIMERG0 or 1 for TIMERG1
timer_num – Timer index, 0 for hw_timer[0] & 1 for hw_timer[1]
time – Pointer, type of double*, to accept timer counter value, in seconds.

返回

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)

Set counter value to hardware timer.

参数

group_num – Timer group, 0 for TIMERG0 or 1 for TIMERG1
timer_num – Timer index, 0 for hw_timer[0] & 1 for hw_timer[1]
load_val – Counter value to write to the hardware timer.

返回

ESP_OK Success
ESP_ERR_INVALID_ARG Parameter error

esp_err_t timer_start(timer_group_t group_num, timer_idx_t timer_num)

Start the counter of hardware timer.

参数

group_num – Timer group number, 0 for TIMERG0 or 1 for TIMERG1
timer_num – Timer index, 0 for hw_timer[0] & 1 for hw_timer[1]

返回

ESP_OK Success
ESP_ERR_INVALID_ARG Parameter error

esp_err_t timer_pause(timer_group_t group_num, timer_idx_t timer_num)

Pause the counter of hardware timer.

参数

group_num – Timer group number, 0 for TIMERG0 or 1 for TIMERG1
timer_num – Timer index, 0 for hw_timer[0] & 1 for hw_timer[1]

返回

ESP_OK Success
ESP_ERR_INVALID_ARG Parameter error

esp_err_t timer_set_counter_mode(timer_group_t group_num, timer_idx_t timer_num, timer_count_dir_t counter_dir)

Set counting mode for hardware timer.

参数

group_num – Timer group number, 0 for TIMERG0 or 1 for TIMERG1
timer_num – Timer index, 0 for hw_timer[0] & 1 for hw_timer[1]
counter_dir – Counting direction of timer, count-up or count-down

返回

ESP_OK Success
ESP_ERR_INVALID_ARG Parameter error

esp_err_t timer_set_auto_reload(timer_group_t group_num, timer_idx_t timer_num, timer_autoreload_t reload)

Enable or disable counter reload function when alarm event occurs.

参数

group_num – Timer group number, 0 for TIMERG0 or 1 for TIMERG1
timer_num – Timer index, 0 for hw_timer[0] & 1 for hw_timer[1]
reload – Counter reload mode.

返回

ESP_OK Success
ESP_ERR_INVALID_ARG Parameter error

esp_err_t timer_set_divider(timer_group_t group_num, timer_idx_t timer_num, uint32_t divider)

Set hardware divider of the source clock to the timer group. By default, the source clock is APB clock running at 80 MHz. For more information, please check Chapter Reset and Clock in Chip Technical Reference Manual.

参数

group_num – Timer group number, 0 for TIMERG0 or 1 for TIMERG1
timer_num – Timer index, 0 for hw_timer[0] & 1 for hw_timer[1]
divider – Timer clock divider value. The divider’s range is from from 2 to 65536.

返回

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)

Set timer alarm value.

参数

group_num – Timer group, 0 for TIMERG0 or 1 for TIMERG1
timer_num – Timer index, 0 for hw_timer[0] & 1 for hw_timer[1]
alarm_value – A 64-bit value to set the alarm value.

返回

ESP_OK Success
ESP_ERR_INVALID_ARG Parameter error

esp_err_t timer_get_alarm_value(timer_group_t group_num, timer_idx_t timer_num, uint64_t *alarm_value)

Get timer alarm value.

参数

group_num – Timer group, 0 for TIMERG0 or 1 for TIMERG1
timer_num – Timer index, 0 for hw_timer[0] & 1 for hw_timer[1]
alarm_value – Pointer of A 64-bit value to accept the alarm value.

返回

ESP_OK Success
ESP_ERR_INVALID_ARG Parameter error

esp_err_t timer_set_alarm(timer_group_t group_num, timer_idx_t timer_num, timer_alarm_t alarm_en)

Enable or disable generation of timer alarm events.

参数

group_num – Timer group, 0 for TIMERG0 or 1 for TIMERG1
timer_num – Timer index, 0 for hw_timer[0] & 1 for hw_timer[1]
alarm_en – To enable or disable timer alarm function.

返回

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)

Add ISR handle callback for the corresponding timer.

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.

备注

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.

参数

group_num – Timer group number
timer_num – Timer index of timer group
isr_handler – Interrupt handler function, it is a callback function.
arg – Parameter for handler function
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.

返回

ESP_OK Success
ESP_ERR_INVALID_ARG Parameter error

esp_err_t timer_isr_callback_remove(timer_group_t group_num, timer_idx_t timer_num)

Remove ISR handle callback for the corresponding timer.

参数

group_num – Timer group number
timer_num – Timer index of timer group

返回

ESP_OK Success
ESP_ERR_INVALID_ARG Parameter error

esp_err_t timer_isr_register(timer_group_t group_num, timer_idx_t timer_num, void (*fn)(void*), void *arg, int intr_alloc_flags, timer_isr_handle_t *handle)

Register Timer interrupt handler, the handler is an ISR. The handler will be attached to the same CPU core that this function is running on.

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. Use direct register access to configure timers from inside the ISR in this case.

备注

If use this function to reigster ISR, you need to write the whole ISR. In the interrupt handler, you need to call timer_spinlock_take(..) before your handling, and call timer_spinlock_give(…) after your handling.

参数

group_num – Timer group number
timer_num – Timer index of timer group
fn – Interrupt handler function.
arg – Parameter for handler function
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.
handle – Pointer to return handle. If non-NULL, a handle for the interrupt will be returned here.

返回

ESP_OK Success
ESP_ERR_INVALID_ARG Parameter error

esp_err_t timer_init(timer_group_t group_num, timer_idx_t timer_num, const timer_config_t *config)

Initializes and configure the timer.

参数

group_num – Timer group number, 0 for TIMERG0 or 1 for TIMERG1
timer_num – Timer index, 0 for hw_timer[0] & 1 for hw_timer[1]
config – Pointer to timer initialization parameters.

返回

ESP_OK Success
ESP_ERR_INVALID_ARG Parameter error

esp_err_t timer_deinit(timer_group_t group_num, timer_idx_t timer_num)

Deinitializes the timer.

参数

group_num – Timer group number, 0 for TIMERG0 or 1 for TIMERG1
timer_num – Timer index, 0 for hw_timer[0] & 1 for hw_timer[1]

返回

ESP_OK Success
ESP_ERR_INVALID_ARG Parameter error

esp_err_t timer_get_config(timer_group_t group_num, timer_idx_t timer_num, timer_config_t *config)

Get timer configure value.

参数

group_num – Timer group number, 0 for TIMERG0 or 1 for TIMERG1
timer_num – Timer index, 0 for hw_timer[0] & 1 for hw_timer[1]
config – Pointer of struct to accept timer parameters.

返回

ESP_OK Success
ESP_ERR_INVALID_ARG Parameter error

esp_err_t timer_group_intr_enable(timer_group_t group_num, timer_intr_t intr_mask)

Enable timer group interrupt, by enable mask.

参数

group_num – Timer group number, 0 for TIMERG0 or 1 for TIMERG1
intr_mask – Timer interrupt enable mask.
- TIMER_INTR_T0: t0 interrupt
- TIMER_INTR_T1: t1 interrupt
- TIMER_INTR_WDT: watchdog interrupt

返回

ESP_OK Success
ESP_ERR_INVALID_ARG Parameter error

esp_err_t timer_group_intr_disable(timer_group_t group_num, timer_intr_t intr_mask)

Disable timer group interrupt, by disable mask.

参数

group_num – Timer group number, 0 for TIMERG0 or 1 for TIMERG1
intr_mask – Timer interrupt disable mask.
- TIMER_INTR_T0: t0 interrupt
- TIMER_INTR_T1: t1 interrupt
- TIMER_INTR_WDT: watchdog interrupt

返回

ESP_OK Success
ESP_ERR_INVALID_ARG Parameter error

esp_err_t timer_enable_intr(timer_group_t group_num, timer_idx_t timer_num)

Enable timer interrupt.

参数

group_num – Timer group number, 0 for TIMERG0 or 1 for TIMERG1
timer_num – Timer index.

返回

ESP_OK Success
ESP_ERR_INVALID_ARG Parameter error

esp_err_t timer_disable_intr(timer_group_t group_num, timer_idx_t timer_num)

Disable timer interrupt.

参数

group_num – Timer group number, 0 for TIMERG0 or 1 for TIMERG1
timer_num – Timer index.

返回

ESP_OK Success
ESP_ERR_INVALID_ARG Parameter error

void timer_group_intr_clr_in_isr(timer_group_t group_num, timer_idx_t timer_num)

Clear timer interrupt status, just used in ISR.

参数

group_num – Timer group number, 0 for TIMERG0 or 1 for TIMERG1
timer_num – Timer index.

void timer_group_clr_intr_status_in_isr(timer_group_t group_num, timer_idx_t timer_num)

Clear timer interrupt status, just used in ISR.

参数

group_num – Timer group number, 0 for TIMERG0 or 1 for TIMERG1
timer_num – Timer index.

void timer_group_enable_alarm_in_isr(timer_group_t group_num, timer_idx_t timer_num)

Enable alarm interrupt, just used in ISR.

参数

group_num – Timer group number, 0 for TIMERG0 or 1 for TIMERG1
timer_num – Timer index.

uint64_t timer_group_get_counter_value_in_isr(timer_group_t group_num, timer_idx_t timer_num)

Get the current counter value, just used in ISR.

参数

group_num – Timer group number, 0 for TIMERG0 or 1 for TIMERG1
timer_num – Timer index.

返回

Counter value

void timer_group_set_alarm_value_in_isr(timer_group_t group_num, timer_idx_t timer_num, uint64_t alarm_val)

Set the alarm threshold for the timer, just used in ISR.

参数

group_num – Timer group number, 0 for TIMERG0 or 1 for TIMERG1
timer_num – Timer index.
alarm_val – Alarm threshold.

void timer_group_set_counter_enable_in_isr(timer_group_t group_num, timer_idx_t timer_num, timer_start_t counter_en)

Enable/disable a counter, just used in ISR.

参数

group_num – Timer group number, 0 for TIMERG0 or 1 for TIMERG1
timer_num – Timer index.
counter_en – Enable/disable.

timer_intr_t timer_group_intr_get_in_isr(timer_group_t group_num)

Get the masked interrupt status, just used in ISR.

参数

group_num – Timer group number, 0 for TIMERG0 or 1 for TIMERG1

返回

Interrupt status

uint32_t timer_group_get_intr_status_in_isr(timer_group_t group_num)

Get interrupt status, just used in ISR.

参数

group_num – Timer group number, 0 for TIMERG0 or 1 for TIMERG1

返回

Interrupt status

void timer_group_clr_intr_sta_in_isr(timer_group_t group_num, timer_intr_t intr_mask)

Clear the masked interrupt status, just used in ISR.

参数

group_num – Timer group number, 0 for TIMERG0 or 1 for TIMERG1
intr_mask – Masked interrupt.

bool timer_group_get_auto_reload_in_isr(timer_group_t group_num, timer_idx_t timer_num)

Get auto reload enable status, just used in ISR.

参数

group_num – Timer group number, 0 for TIMERG0 or 1 for TIMERG1
timer_num – Timer index

返回

True Auto reload enabled
False Auto reload disabled

esp_err_t timer_spinlock_take(timer_group_t group_num)

Take timer spinlock to enter critical protect.

备注

Deprecated, the recommended way is to use ISR callbacks instead, see timer_group_example_main

参数

group_num – Timer group number, 0 for TIMERG0 or 1 for TIMERG1

返回

ESP_OK Success
ESP_ERR_INVALID_ARG Parameter error

esp_err_t timer_spinlock_give(timer_group_t group_num)

Give timer spinlock to exit critical protect.

备注

Deprecated, the recommended way is to use ISR callbacks instead, see timer_group_example_main

参数

group_num – Timer group number, 0 for TIMERG0 or 1 for TIMERG1

返回

ESP_OK Success
ESP_ERR_INVALID_ARG Parameter error

Macros

TIMER_BASE_CLK: Frequency of the clock on the input of the timer groups

Type Definitions

typedef bool (*timer_isr_t)(void*)

Interrupt handle callback function. User need to retrun a bool value in callback.

备注

If you called FreeRTOS functions in callback, you need to return true or false based on the retrun value of argument pxHigherPriorityTaskWoken. For example, xQueueSendFromISR is called in callback, if the return value pxHigherPriorityTaskWoken of any FreeRTOS calls is pdTRUE, return true; otherwise return false.

Return

True Do task yield at the end of ISR
False Not do task yield at the end of ISR

typedef intr_handle_t timer_isr_handle_t: Interrupt handle, used in order to free the isr after use. Aliases to an int handle for now.

Header File

components/hal/include/hal/timer_types.h

Structures

struct timer_config_t

Data structure with timer’s configuration settings.

Public Members

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.

timer_src_clk_t clk_src: Use XTAL as source clock.

Enumerations

enum timer_group_t

Selects a Timer-Group out of 2 available groups.

Values:

enumerator TIMER_GROUP_0: Hw timer group 0

enumerator TIMER_GROUP_1: Hw timer group 1

enumerator TIMER_GROUP_MAX

enum timer_idx_t

Select a hardware timer from timer groups.

Values:

enumerator TIMER_0: Select timer0 of GROUPx

enumerator TIMER_1: Select timer1 of GROUPx

enumerator TIMER_MAX

enum timer_count_dir_t

Decides the direction of counter.

Values:

enumerator TIMER_COUNT_DOWN: Descending Count from cnt.high|cnt.low

enumerator TIMER_COUNT_UP: Ascending Count from Zero

enumerator TIMER_COUNT_MAX

enum timer_start_t

Decides whether timer is on or paused.

Values:

enumerator TIMER_PAUSE: Pause timer counter

enumerator TIMER_START: Start timer counter

enum timer_intr_t

Interrupt types of the timer.

Values:

enumerator TIMER_INTR_T0: interrupt of timer 0

enumerator TIMER_INTR_T1: interrupt of timer 1

enumerator TIMER_INTR_WDT: interrupt of watchdog

enumerator TIMER_INTR_NONE

enum timer_alarm_t

Decides whether to enable alarm mode.

Values:

enumerator TIMER_ALARM_DIS: Disable timer alarm

enumerator TIMER_ALARM_EN: Enable timer alarm

enumerator TIMER_ALARM_MAX

enum timer_intr_mode_t

Select interrupt type if running in alarm mode.

Values:

enumerator TIMER_INTR_LEVEL: Interrupt mode: level mode

enumerator TIMER_INTR_MAX

enum timer_autoreload_t

Select if Alarm needs to be loaded by software or automatically reload by hardware.

Values:

enumerator TIMER_AUTORELOAD_DIS: Disable auto-reload: hardware will not load counter value after an alarm event

enumerator TIMER_AUTORELOAD_EN: Enable auto-reload: hardware will load counter value after an alarm event

enumerator TIMER_AUTORELOAD_MAX

enum timer_src_clk_t

Select timer source clock.

Values:

enumerator TIMER_SRC_CLK_APB: Select APB as the source clock

enumerator TIMER_SRC_CLK_XTAL: Select XTAL as the source clock

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