General Purpose Timer (GPTimer)

Introduction

GPTimer (General Purpose Timer) is the driver of ESP32-H2 Timer Group peripheral. The hardware timer features high resolution and flexible alarm action. The behavior when the internal counter of a timer reaches a specific target value is called a timer alarm. When a timer alarms, a user registered per-timer callback would be called.

Typically, a general purpose timer can be used in scenarios like:

  • Free running as a wall clock, fetching a high-resolution timestamp at any time and any places

  • Generate period alarms, trigger events periodically

  • Generate one-shot alarm, respond in target time

Functional Overview

The following sections of this document cover the typical steps to install and operate a timer:

  • Resource Allocation - covers which parameters should be set up to get a timer handle and how to recycle the resources when GPTimer finishes working.

  • Set and Get Count Value - covers how to force the timer counting from a start point and how to get the count value at anytime.

  • Set up Alarm Action - covers the parameters that should be set up to enable the alarm event.

  • Register Event Callbacks - covers how to hook user specific code to the alarm event callback function.

  • Enable and Disable Timer - covers how to enable and disable the timer.

  • Start and Stop Timer - shows some typical use cases that start the timer with different alarm behavior.

  • ETM Event and Task - describes what the events and tasks can be connected to the ETM channel.

  • Power Management - describes how different source clock selections can affect power consumption.

  • IRAM Safe - describes tips on how to make the timer interrupt and IO control functions work better along with a disabled cache.

  • Thread Safety - lists which APIs are guaranteed to be thread safe by the driver.

  • Kconfig Options - lists the supported Kconfig options that can be used to make a different effect on driver behavior.

Resource Allocation

Different ESP chips might have different numbers of independent timer groups, and within each group, there could also be several independent timers. 1

A GPTimer instance is represented by gptimer_handle_t. The driver behind will manage all available hardware resources in a pool, so that you do not need to care about which timer and which group it belongs to.

To install a timer instance, there is a configuration structure that needs to be given in advance: gptimer_config_t:

With all the above configurations set in the structure, the structure can be passed to gptimer_new_timer() which will instantiate the timer instance and return a handle of the timer.

The function can fail due to various errors such as insufficient memory, invalid arguments, etc. Specifically, when there are no more free timers (i.e. all hardware resources have been used up), then ESP_ERR_NOT_FOUND will be returned. The total number of available timers is represented by the SOC_TIMER_GROUP_TOTAL_TIMERS and its value will depend on the ESP chip.

If a previously created GPTimer instance is no longer required, you should recycle the timer by calling gptimer_del_timer(). This will allow the underlying HW timer to be used for other purposes. Before deleting a GPTimer handle, please disable it by gptimer_disable() in advance or make sure it has not enabled yet by gptimer_enable().

Creating a GPTimer Handle with Resolution of 1 MHz

gptimer_handle_t gptimer = NULL;
gptimer_config_t timer_config = {
    .clk_src = GPTIMER_CLK_SRC_DEFAULT,
    .direction = GPTIMER_COUNT_UP,
    .resolution_hz = 1 * 1000 * 1000, // 1MHz, 1 tick = 1us
};
ESP_ERROR_CHECK(gptimer_new_timer(&timer_config, &gptimer));

Set and Get Count Value

When the GPTimer is created, the internal counter will be reset to zero by default. The counter value can be updated asynchronously by gptimer_set_raw_count(). The maximum count value is dependent on the bit width of the hardware timer, which is also reflected by the SOC macro SOC_TIMER_GROUP_COUNTER_BIT_WIDTH. When updating the raw count of an active timer, the timer will immediately start counting from the new value.

Count value can be retrieved by gptimer_get_raw_count(), at any time.

Set up Alarm Action

For most of the use cases of GPTimer, you should set up the alarm action before starting the timer, except for the simple wall-clock scenario, where a free running timer is enough. To set up the alarm action, you should configure several members of gptimer_alarm_config_t based on how you make use of the alarm event:

To make the alarm configurations take effect, you should call gptimer_set_alarm_action(). Especially, if gptimer_alarm_config_t is set to NULL, the alarm function will be disabled.

Note

If an alarm value is set and the timer has already exceeded this value, the alarm will be triggered immediately.

Register Event Callbacks

After the timer starts up, it can generate a specific event (e.g. the "Alarm Event") dynamically. If you have some functions that should be called when the event happens, please hook your function to the interrupt service routine by calling gptimer_register_event_callbacks(). All supported event callbacks are listed in gptimer_event_callbacks_t:

  • gptimer_event_callbacks_t::on_alarm sets a callback function for alarm events. As this function is called within the ISR context, you must ensure that the function does not attempt to block (e.g., by making sure that only FreeRTOS APIs with ISR suffix are called from within the function). The function prototype is declared in gptimer_alarm_cb_t.

You can save your own context to gptimer_register_event_callbacks() as well, via the parameter user_data. The user data will be directly passed to the callback function.

This function will lazy install the interrupt service for the timer but not enable it. So please call this function before gptimer_enable(), otherwise the ESP_ERR_INVALID_STATE error will be returned. See Section Enable and Disable Timer for more information.

Enable and Disable Timer

Before doing IO control to the timer, you needs to enable the timer first, by calling gptimer_enable(). This function will:

  • Switch the timer driver state from init to enable.

  • Enable the interrupt service if it has been lazy installed by gptimer_register_event_callbacks().

  • Acquire a proper power management lock if a specific clock source (e.g. APB clock) is selected. See Section Power Management for more information.

Calling gptimer_disable() will do the opposite, that is, put the timer driver back to the init state, disable the interrupts service and release the power management lock.

Start and Stop Timer

The basic IO operation of a timer is to start and stop. Calling gptimer_start() can make the internal counter work, while calling gptimer_stop() can make the counter stop working. The following illustrates how to start a timer with or without an alarm event. Calling gptimer_start() will transit the driver state from enable to run, and vice versa. You need to make sure the start and stop functions are used in pairs, otherwise, the functions may return ESP_ERR_INVALID_STATE. Most of the time, this error means that the timer is already stopped or in the "start protection" state (i.e. gptimer_start() is called but not finished).

Start Timer as a Wall Clock

ESP_ERROR_CHECK(gptimer_enable(gptimer));
ESP_ERROR_CHECK(gptimer_start(gptimer));
// Retrieve the timestamp at any time
uint64_t count;
ESP_ERROR_CHECK(gptimer_get_raw_count(gptimer, &count));

Trigger Period Events

typedef struct {
    uint64_t event_count;
} example_queue_element_t;

static bool example_timer_on_alarm_cb(gptimer_handle_t timer, const gptimer_alarm_event_data_t *edata, void *user_ctx)
{
    BaseType_t high_task_awoken = pdFALSE;
    QueueHandle_t queue = (QueueHandle_t)user_ctx;
    // Retrieve the count value from event data
    example_queue_element_t ele = {
        .event_count = edata->count_value
    };
    // Optional: send the event data to other task by OS queue
    // Do not introduce complex logics in callbacks
    // Suggest dealing with event data in the main loop, instead of in this callback
    xQueueSendFromISR(queue, &ele, &high_task_awoken);
    // return whether we need to yield at the end of ISR
    return high_task_awoken == pdTRUE;
}

gptimer_alarm_config_t alarm_config = {
    .reload_count = 0, // counter will reload with 0 on alarm event
    .alarm_count = 1000000, // period = 1s @resolution 1MHz
    .flags.auto_reload_on_alarm = true, // enable auto-reload
};
ESP_ERROR_CHECK(gptimer_set_alarm_action(gptimer, &alarm_config));

gptimer_event_callbacks_t cbs = {
    .on_alarm = example_timer_on_alarm_cb, // register user callback
};
ESP_ERROR_CHECK(gptimer_register_event_callbacks(gptimer, &cbs, queue));
ESP_ERROR_CHECK(gptimer_enable(gptimer));
ESP_ERROR_CHECK(gptimer_start(gptimer));

Trigger One-Shot Event

typedef struct {
    uint64_t event_count;
} example_queue_element_t;

static bool example_timer_on_alarm_cb(gptimer_handle_t timer, const gptimer_alarm_event_data_t *edata, void *user_ctx)
{
    BaseType_t high_task_awoken = pdFALSE;
    QueueHandle_t queue = (QueueHandle_t)user_ctx;
    // Stop timer the sooner the better
    gptimer_stop(timer);
    // Retrieve the count value from event data
    example_queue_element_t ele = {
        .event_count = edata->count_value
    };
    // Optional: send the event data to other task by OS queue
    xQueueSendFromISR(queue, &ele, &high_task_awoken);
    // return whether we need to yield at the end of ISR
    return high_task_awoken == pdTRUE;
}

gptimer_alarm_config_t alarm_config = {
    .alarm_count = 1 * 1000 * 1000, // alarm target = 1s @resolution 1MHz
};
ESP_ERROR_CHECK(gptimer_set_alarm_action(gptimer, &alarm_config));

gptimer_event_callbacks_t cbs = {
    .on_alarm = example_timer_on_alarm_cb, // register user callback
};
ESP_ERROR_CHECK(gptimer_register_event_callbacks(gptimer, &cbs, queue));
ESP_ERROR_CHECK(gptimer_enable(gptimer));
ESP_ERROR_CHECK(gptimer_start(gptimer));

Dynamic Alarm Update

Alarm value can be updated dynamically inside the ISR handler callback, by changing gptimer_alarm_event_data_t::alarm_value. Then the alarm value will be updated after the callback function returns.

typedef struct {
    uint64_t event_count;
} example_queue_element_t;

static bool example_timer_on_alarm_cb(gptimer_handle_t timer, const gptimer_alarm_event_data_t *edata, void *user_ctx)
{
    BaseType_t high_task_awoken = pdFALSE;
    QueueHandle_t queue = (QueueHandle_t)user_data;
    // Retrieve the count value from event data
    example_queue_element_t ele = {
        .event_count = edata->count_value
    };
    // Optional: send the event data to other task by OS queue
    xQueueSendFromISR(queue, &ele, &high_task_awoken);
    // reconfigure alarm value
    gptimer_alarm_config_t alarm_config = {
        .alarm_count = edata->alarm_value + 1000000, // alarm in next 1s
    };
    gptimer_set_alarm_action(timer, &alarm_config);
    // return whether we need to yield at the end of ISR
    return high_task_awoken == pdTRUE;
}

gptimer_alarm_config_t alarm_config = {
    .alarm_count = 1000000, // initial alarm target = 1s @resolution 1MHz
};
ESP_ERROR_CHECK(gptimer_set_alarm_action(gptimer, &alarm_config));

gptimer_event_callbacks_t cbs = {
    .on_alarm = example_timer_on_alarm_cb, // register user callback
};
ESP_ERROR_CHECK(gptimer_register_event_callbacks(gptimer, &cbs, queue));
ESP_ERROR_CHECK(gptimer_enable(gptimer));
ESP_ERROR_CHECK(gptimer_start(gptimer));

ETM Event and Task

GPTimer is able to generate various events that can interact with the ETM module. The supported events are listed in the gptimer_etm_event_type_t. You can call gptimer_new_etm_event() to get the corresponding ETM event handle. Likewise, GPTimer exposes several tasks that can be triggered by other ETM events. The supported tasks are listed in the gptimer_etm_task_type_t. You can call gptimer_new_etm_task() to get the corresponding ETM task handle.

For how to connect the event and task to an ETM channel, please refer to the ETM documentation.

Power Management

There're some power management strategies, which might turn off or change the frequency of GPTimer's source clock to save power consumption. For example, during DFS, APB clock will be scaled down. If light-sleep is also enabled, PLL and XTAL clocks will be powered off. Both of them can result in an inaccurate time keeping.

The driver can prevent the above situation from happening by creating different power management lock according to different clock source. The driver will increase the reference count of that power management lock in the gptimer_enable() and decrease it in the gptimer_disable(). So we can ensure the clock source is stable between gptimer_enable() and gptimer_disable().

IRAM Safe

By default, the GPTimer interrupt will be deferred when the cache is disabled because of writing or erasing the flash. Thus the alarm interrupt will not get executed in time, which is not expected in a real-time application.

There is a Kconfig option CONFIG_GPTIMER_ISR_IRAM_SAFE that will:

  • Enable the interrupt being serviced even when the cache is disabled

  • Place all functions that used by the ISR into IRAM 2

  • Place driver object into DRAM (in case it is mapped to PSRAM by accident)

This will allow the interrupt to run while the cache is disabled, but will come at the cost of increased IRAM consumption.

There is another Kconfig option CONFIG_GPTIMER_CTRL_FUNC_IN_IRAM that can put commonly used IO control functions into IRAM as well. So, these functions can also be executable when the cache is disabled. These IO control functions are as follows:

Thread Safety

All the APIs provided by the driver are guaranteed to be thread safe, which means you can call them from different RTOS tasks without protection by extra locks. The following functions are allowed to run under ISR context.

Kconfig Options

Application Examples

API Reference

Header File

Functions

esp_err_t gptimer_new_timer(const gptimer_config_t *config, gptimer_handle_t *ret_timer)

Create a new General Purpose Timer, and return the handle.

Note

The newly created timer is put in the "init" state.

Parameters

  • config -- [in] GPTimer configuration

  • ret_timer -- [out] Returned timer handle

Returns

  • ESP_OK: Create GPTimer successfully

  • ESP_ERR_INVALID_ARG: Create GPTimer failed because of invalid argument

  • ESP_ERR_NO_MEM: Create GPTimer failed because out of memory

  • ESP_ERR_NOT_FOUND: Create GPTimer failed because all hardware timers are used up and no more free one

  • ESP_FAIL: Create GPTimer failed because of other error

esp_err_t gptimer_del_timer(gptimer_handle_t timer)

Delete the GPTimer handle.

Note

A timer must be in the "init" state before it can be deleted.

Parameters

timer -- [in] Timer handle created by gptimer_new_timer

Returns

  • ESP_OK: Delete GPTimer successfully

  • ESP_ERR_INVALID_ARG: Delete GPTimer failed because of invalid argument

  • ESP_ERR_INVALID_STATE: Delete GPTimer failed because the timer is not in init state

  • ESP_FAIL: Delete GPTimer failed because of other error

esp_err_t gptimer_set_raw_count(gptimer_handle_t timer, uint64_t value)

Set GPTimer raw count value.

Note

When updating the raw count of an active timer, the timer will immediately start counting from the new value.

Note

This function is allowed to run within ISR context

Note

If CONFIG_GPTIMER_CTRL_FUNC_IN_IRAM is enabled, this function will be placed in the IRAM by linker, makes it possible to execute even when the Flash Cache is disabled.

Parameters

  • timer -- [in] Timer handle created by gptimer_new_timer

  • value -- [in] Count value to be set

Returns

  • ESP_OK: Set GPTimer raw count value successfully

  • ESP_ERR_INVALID_ARG: Set GPTimer raw count value failed because of invalid argument

  • ESP_FAIL: Set GPTimer raw count value failed because of other error

esp_err_t gptimer_get_raw_count(gptimer_handle_t timer, uint64_t *value)

Get GPTimer raw count value.

Note

This function will trigger a software capture event and then return the captured count value.

Note

With the raw count value and the resolution returned from gptimer_get_resolution, you can convert the count value into seconds.

Note

This function is allowed to run within ISR context

Note

If CONFIG_GPTIMER_CTRL_FUNC_IN_IRAM is enabled, this function will be placed in the IRAM by linker, makes it possible to execute even when the Flash Cache is disabled.

Parameters

  • timer -- [in] Timer handle created by gptimer_new_timer

  • value -- [out] Returned GPTimer count value

Returns

  • ESP_OK: Get GPTimer raw count value successfully

  • ESP_ERR_INVALID_ARG: Get GPTimer raw count value failed because of invalid argument

  • ESP_FAIL: Get GPTimer raw count value failed because of other error

esp_err_t gptimer_get_resolution(gptimer_handle_t timer, uint32_t *out_resolution)

Return the real resolution of the timer.

Note

usually the timer resolution is same as what you configured in the gptimer_config_t::resolution_hz, but some unstable clock source (e.g. RC_FAST) will do a calibration, the real resolution can be different from the configured one.

Parameters

  • timer -- [in] Timer handle created by gptimer_new_timer

  • out_resolution -- [out] Returned timer resolution, in Hz

Returns

  • ESP_OK: Get GPTimer resolution successfully

  • ESP_ERR_INVALID_ARG: Get GPTimer resolution failed because of invalid argument

  • ESP_FAIL: Get GPTimer resolution failed because of other error

esp_err_t gptimer_get_captured_count(gptimer_handle_t timer, uint64_t *value)

Get GPTimer captured count value.

Note

The capture action can be issued either by ETM event or by software (see also gptimer_get_raw_count).

Note

This function is allowed to run within ISR context

Note

If CONFIG_GPTIMER_CTRL_FUNC_IN_IRAM is enabled, this function will be placed in the IRAM by linker, makes it possible to execute even when the Flash Cache is disabled.

Parameters

  • timer -- [in] Timer handle created by gptimer_new_timer

  • value -- [out] Returned captured count value

Returns

  • ESP_OK: Get GPTimer captured count value successfully

  • ESP_ERR_INVALID_ARG: Get GPTimer captured count value failed because of invalid argument

  • ESP_FAIL: Get GPTimer captured count value failed because of other error

esp_err_t gptimer_register_event_callbacks(gptimer_handle_t timer, const gptimer_event_callbacks_t *cbs, void *user_data)

Set callbacks for GPTimer.

Note

User registered callbacks are expected to be runnable within ISR context

Note

The first call to this function needs to be before the call to gptimer_enable

Note

User can deregister a previously registered callback by calling this function and setting the callback member in the cbs structure to NULL.

Parameters

  • timer -- [in] Timer handle created by gptimer_new_timer

  • cbs -- [in] Group of callback functions

  • user_data -- [in] User data, which will be passed to callback functions directly

Returns

  • ESP_OK: Set event callbacks successfully

  • ESP_ERR_INVALID_ARG: Set event callbacks failed because of invalid argument

  • ESP_ERR_INVALID_STATE: Set event callbacks failed because the timer is not in init state

  • ESP_FAIL: Set event callbacks failed because of other error

esp_err_t gptimer_set_alarm_action(gptimer_handle_t timer, const gptimer_alarm_config_t *config)

Set alarm event actions for GPTimer.

Note

This function is allowed to run within ISR context, so that user can set new alarm action immediately in the ISR callback.

Note

If CONFIG_GPTIMER_CTRL_FUNC_IN_IRAM is enabled, this function will be placed in the IRAM by linker, makes it possible to execute even when the Flash Cache is disabled.

Parameters

  • timer -- [in] Timer handle created by gptimer_new_timer

  • config -- [in] Alarm configuration, especially, set config to NULL means disabling the alarm function

Returns

  • ESP_OK: Set alarm action for GPTimer successfully

  • ESP_ERR_INVALID_ARG: Set alarm action for GPTimer failed because of invalid argument

  • ESP_FAIL: Set alarm action for GPTimer failed because of other error

esp_err_t gptimer_enable(gptimer_handle_t timer)

Enable GPTimer.

Note

This function will transit the timer state from "init" to "enable".

Note

This function will enable the interrupt service, if it's lazy installed in gptimer_register_event_callbacks.

Note

This function will acquire a PM lock, if a specific source clock (e.g. APB) is selected in the gptimer_config_t, while CONFIG_PM_ENABLE is enabled.

Note

Enable a timer doesn't mean to start it. See also gptimer_start for how to make the timer start counting.

Parameters

timer -- [in] Timer handle created by gptimer_new_timer

Returns

  • ESP_OK: Enable GPTimer successfully

  • ESP_ERR_INVALID_ARG: Enable GPTimer failed because of invalid argument

  • ESP_ERR_INVALID_STATE: Enable GPTimer failed because the timer is already enabled

  • ESP_FAIL: Enable GPTimer failed because of other error

esp_err_t gptimer_disable(gptimer_handle_t timer)

Disable GPTimer.

Note

This function will transit the timer state from "enable" to "init".

Note

This function will disable the interrupt service if it's installed.

Note

This function will release the PM lock if it's acquired in the gptimer_enable.

Note

Disable a timer doesn't mean to stop it. See also gptimer_stop for how to make the timer stop counting.

Parameters

timer -- [in] Timer handle created by gptimer_new_timer

Returns

  • ESP_OK: Disable GPTimer successfully

  • ESP_ERR_INVALID_ARG: Disable GPTimer failed because of invalid argument

  • ESP_ERR_INVALID_STATE: Disable GPTimer failed because the timer is not enabled yet

  • ESP_FAIL: Disable GPTimer failed because of other error

esp_err_t gptimer_start(gptimer_handle_t timer)

Start GPTimer (internal counter starts counting)

Note

This function will transit the timer state from "enable" to "run".

Note

This function is allowed to run within ISR context

Note

If CONFIG_GPTIMER_CTRL_FUNC_IN_IRAM is enabled, this function will be placed in the IRAM by linker, makes it possible to execute even when the Flash Cache is disabled.

Parameters

timer -- [in] Timer handle created by gptimer_new_timer

Returns

  • ESP_OK: Start GPTimer successfully

  • ESP_ERR_INVALID_ARG: Start GPTimer failed because of invalid argument

  • ESP_ERR_INVALID_STATE: Start GPTimer failed because the timer is not enabled or is already in running

  • ESP_FAIL: Start GPTimer failed because of other error

esp_err_t gptimer_stop(gptimer_handle_t timer)

Stop GPTimer (internal counter stops counting)

Note

This function will transit the timer state from "run" to "enable".

Note

This function is allowed to run within ISR context

Note

If CONFIG_GPTIMER_CTRL_FUNC_IN_IRAM is enabled, this function will be placed in the IRAM by linker, makes it possible to execute even when the Flash Cache is disabled.

Parameters

timer -- [in] Timer handle created by gptimer_new_timer

Returns

  • ESP_OK: Stop GPTimer successfully

  • ESP_ERR_INVALID_ARG: Stop GPTimer failed because of invalid argument

  • ESP_ERR_INVALID_STATE: Stop GPTimer failed because the timer is not in running.

  • ESP_FAIL: Stop GPTimer failed because of other error

Structures

struct gptimer_config_t

General Purpose Timer configuration.

Public Members

gptimer_clock_source_t clk_src

GPTimer clock source

gptimer_count_direction_t direction

Count direction

uint32_t resolution_hz

Counter resolution (working frequency) in Hz, hence, the step size of each count tick equals to (1 / resolution_hz) seconds

int intr_priority

GPTimer interrupt priority, if set to 0, the driver will try to allocate an interrupt with a relative low priority (1,2,3)

uint32_t intr_shared

Set true, the timer interrupt number can be shared with other peripherals

struct gptimer_config_t::[anonymous] flags

GPTimer config flags

struct gptimer_event_callbacks_t

Group of supported GPTimer callbacks.

Note

The callbacks are all running under ISR environment

Note

When CONFIG_GPTIMER_ISR_IRAM_SAFE is enabled, the callback itself and functions called by it should be placed in IRAM.

Public Members

gptimer_alarm_cb_t on_alarm

Timer alarm callback

struct gptimer_alarm_config_t

General Purpose Timer alarm configuration.

Public Members

uint64_t alarm_count

Alarm target count value

uint64_t reload_count

Alarm reload count value, effect only when auto_reload_on_alarm is set to true

uint32_t auto_reload_on_alarm

Reload the count value by hardware, immediately at the alarm event

struct gptimer_alarm_config_t::[anonymous] flags

Alarm config flags

Header File

Functions

esp_err_t gptimer_new_etm_event(gptimer_handle_t timer, const gptimer_etm_event_config_t *config, esp_etm_event_handle_t *out_event)

Get the ETM event for GPTimer.

Note

The created ETM event object can be deleted later by calling esp_etm_del_event

Parameters

  • timer -- [in] Timer handle created by gptimer_new_timer

  • config -- [in] GPTimer ETM event configuration

  • out_event -- [out] Returned ETM event handle

Returns

  • ESP_OK: Get ETM event successfully

  • ESP_ERR_INVALID_ARG: Get ETM event failed because of invalid argument

  • ESP_FAIL: Get ETM event failed because of other error

esp_err_t gptimer_new_etm_task(gptimer_handle_t timer, const gptimer_etm_task_config_t *config, esp_etm_task_handle_t *out_task)

Get the ETM task for GPTimer.

Note

The created ETM task object can be deleted later by calling esp_etm_del_task

Parameters

  • timer -- [in] Timer handle created by gptimer_new_timer

  • config -- [in] GPTimer ETM task configuration

  • out_task -- [out] Returned ETM task handle

Returns

  • ESP_OK: Get ETM task successfully

  • ESP_ERR_INVALID_ARG: Get ETM task failed because of invalid argument

  • ESP_FAIL: Get ETM task failed because of other error

Structures

struct gptimer_etm_event_config_t

GPTimer ETM event configuration.

Public Members

gptimer_etm_event_type_t event_type

GPTimer ETM event type

struct gptimer_etm_task_config_t

GPTimer ETM task configuration.

Public Members

gptimer_etm_task_type_t task_type

GPTimer ETM task type

Header File

Structures

struct gptimer_alarm_event_data_t

GPTimer alarm event data.

Public Members

uint64_t count_value

Current count value

uint64_t alarm_value

Current alarm value

Type Definitions

typedef struct gptimer_t *gptimer_handle_t

Type of General Purpose Timer handle.

typedef bool (*gptimer_alarm_cb_t)(gptimer_handle_t timer, const gptimer_alarm_event_data_t *edata, void *user_ctx)

Timer alarm callback prototype.

Param timer

[in] Timer handle created by gptimer_new_timer

Param edata

[in] Alarm event data, fed by driver

Param user_ctx

[in] User data, passed from gptimer_register_event_callbacks

Return

Whether a high priority task has been waken up by this function

Header File

Type Definitions

typedef soc_periph_gptimer_clk_src_t gptimer_clock_source_t

GPTimer clock source.

Note

User should select the clock source based on the power and resolution requirement

Enumerations

enum gptimer_count_direction_t

GPTimer count direction.

Values:

enumerator GPTIMER_COUNT_DOWN

Decrease count value

enumerator GPTIMER_COUNT_UP

Increase count value

enum gptimer_etm_task_type_t

GPTimer specific tasks that supported by the ETM module.

Values:

enumerator GPTIMER_ETM_TASK_START_COUNT

Start the counter

enumerator GPTIMER_ETM_TASK_STOP_COUNT

Stop the counter

enumerator GPTIMER_ETM_TASK_EN_ALARM

Enable the alarm

enumerator GPTIMER_ETM_TASK_RELOAD

Reload preset value into counter

enumerator GPTIMER_ETM_TASK_CAPTURE

Capture current count value into specific register

enumerator GPTIMER_ETM_TASK_MAX

Maximum number of tasks

enum gptimer_etm_event_type_t

GPTimer specific events that supported by the ETM module.

Values:

enumerator GPTIMER_ETM_EVENT_ALARM_MATCH

Count value matches the alarm target value

enumerator GPTIMER_ETM_EVENT_MAX

Maximum number of events

1

Different ESP chip series might have different numbers of GPTimer instances. For more details, please refer to ESP32-H2 Technical Reference Manual > Chapter Timer Group (TIMG) [PDF]. The driver will not forbid you from applying for more timers, but it will return error when all available hardware resources are used up. Please always check the return value when doing resource allocation (e.g. gptimer_new_timer()).

2

gptimer_event_callbacks_t::on_alarm callback and the functions invoked by the callback should also be placed in IRAM, please take care of them by yourself.

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