# General Purpose Timer (GPTimer)

[中文]

This document introduces the features of the General Purpose Timer (GPTimer) driver in ESP-IDF. The table of contents is as follows:

## Overview

GPTimer is a dedicated driver for the ESP32-P4 [Timer Group peripheral]. This timer can select different clock sources and prescalers to meet the requirements of nanosecond-level resolution. Additionally, it has flexible timeout alarm functions and allows automatic updating of the count value at the alarm moment, achieving very precise timing cycles.

Based on the high resolution, high count range, and high response capabilities of the hardware timer, the main application scenarios of this driver include:

- Running freely as a calendar clock to provide timestamp services for other modules

- Generating periodic alarms to complete periodic tasks

- Generating one-shot alarms, which can be used to implement a monotonic software timer list with asynchronous updates of alarm values

- Working with the GPIO module to achieve PWM signal output and input capture

- etc.

## Quick Start

This section provides a concise overview of how to use the GPTimer driver. Through practical examples, it demonstrates how to initialize and start a timer, configure alarm events, and register callback functions. The typical usage flow is as follows:

GPTimer driver's general usage flow (click to enlarge)

### Creating and Starting a Timer

First, we need to create a timer instance. The following code shows how to create a timer with a resolution of 1 MHz:

    gptimer_handle_t gptimer = NULL;
    gptimer_config_t timer_config = {
        .clk_src = GPTIMER_CLK_SRC_DEFAULT, // Select the default clock source
        .direction = GPTIMER_COUNT_UP,      // Counting direction is up
        .resolution_hz = 1 * 1000 * 1000,   // Resolution is 1 MHz, i.e., 1 tick equals 1 microsecond
    };
    // Create a timer instance
    ESP_ERROR_CHECK(gptimer_new_timer(&timer_config, &gptimer));
    // Enable the timer
    ESP_ERROR_CHECK(gptimer_enable(gptimer));
    // Start the timer
    ESP_ERROR_CHECK(gptimer_start(gptimer));

When creating a timer instance, we need to configure parameters such as the clock source, counting direction, and resolution through `gptimer_config_t`. These parameters determine how the timer works. Then, call the `gptimer_new_timer()` function to create a new timer instance, which returns a handle pointing to the new instance. The timer handle is essentially a pointer to the timer memory object, of type `gptimer_handle_t`.

Here are the other configuration parameters of the `gptimer_config_t` structure and their explanations:

- `gptimer_config_t::clk_src` selects the clock source for the timer. Available clock sources are listed in `gptimer_clock_source_t`, and only one can be selected. Different clock sources vary in resolution, accuracy, and power consumption.

- `gptimer_config_t::direction` sets the counting direction of the timer. Supported directions are listed in `gptimer_count_direction_t`, and only one can be selected.

- `gptimer_config_t::resolution_hz` sets the resolution of the internal counter. Each tick is equivalent to 1 / resolution_hz seconds.

- `gptimer_config_t::intr_priority` sets the interrupt priority. If set to `0`, a default priority interrupt will be allocated; otherwise, the specified priority will be used.

- `gptimer_config_t::flags` is used to fine-tune some behaviors of the driver, including the following options:

  > - `gptimer_config_t::flags::allow_pd` configures whether the driver allows the system to power down the peripheral in sleep mode. Before entering sleep, the system will back up the GPTimer register context, which will be restored when the system wakes up. Note that powering down the peripheral can save power but will consume more memory to save the register context. You need to balance power consumption and memory usage. This configuration option depends on specific hardware features. If enabled on an unsupported chip, you will see an error message like `not able to power down in light sleep`.

Note

Note that if all hardware timers in the current chip have been allocated, `gptimer_new_timer()` will return the `ESP_ERR_NOT_FOUND` error.

Before starting the timer, it must be enabled. The enable function `gptimer_enable()` can switch the internal state machine of the driver to the active state, which includes some system service requests/registrations, such as applying for a power management lock. The corresponding disable function is `gptimer_disable()`, which releases all system services.

Note

When calling the `gptimer_enable()` and `gptimer_disable()` functions, they need to be used in pairs. This means you cannot call `gptimer_enable()` or `gptimer_disable()` twice in a row. This pairing principle ensures the correct management and release of resources.

The `gptimer_start()` function is used to start the timer. After starting, the timer will begin counting and will automatically overflow and restart from 0 when it reaches the maximum or minimum value (depending on the counting direction). The `gptimer_stop()` function is used to stop the timer. Note that stopping a timer does not clear the current value of the counter. To clear the counter, use the `gptimer_set_raw_count()` function introduced later. The `gptimer_start()` and `gptimer_stop()` functions follow the idempotent principle. This means that if the timer is already started, calling the `gptimer_start()` function again will have no effect. Similarly, if the timer is already stopped, calling the `gptimer_stop()` function again will have no effect.

Note

However, note that when the timer is in the intermediate state of starting (the start has begun but not yet completed), if another thread calls the `gptimer_start()` or `gptimer_stop()` function, it will return the `ESP_ERR_INVALID_STATE` error to avoid triggering uncertain behavior.

### Setting and Getting the Count Value

When a timer is newly created, its internal counter value defaults to zero. You can set other count values using the `gptimer_set_raw_count()` function. The maximum count value depends on the bit width of the hardware timer (usually no less than `54 bits`).

Note

If the timer is already running, `gptimer_set_raw_count()` will make the timer immediately jump to the new value and start counting from the newly set value.

The `gptimer_get_raw_count()` function is used to get the current count value of the timer. This count value is the accumulated count since the timer started (assuming it started from 0). Note that the returned value has not been converted to any unit; it is a pure count value. You need to convert the count value to time units based on the actual resolution of the timer. The timer's resolution can be obtained using the `gptimer_get_resolution()` function.

    // Check the timer's resolution
    uint32_t resolution_hz;
    ESP_ERROR_CHECK(gptimer_get_resolution(gptimer, &resolution_hz));
    // Read the current count value
    uint64_t count;
    ESP_ERROR_CHECK(gptimer_get_raw_count(gptimer, &count));
    // (Optional) Convert the count value to time units (seconds)
    double time = (double)count / resolution_hz;

### Triggering Periodic Alarm Events

In addition to the timestamp function, the general-purpose timer also supports alarm functions. The following code shows how to set a periodic alarm that triggers once per second:

    gptimer_handle_t gptimer = NULL;
    gptimer_config_t timer_config = {
        .clk_src = GPTIMER_CLK_SRC_DEFAULT, // Select the default clock source
        .direction = GPTIMER_COUNT_UP,      // Counting direction is up
        .resolution_hz = 1 * 1000 * 1000,   // Resolution is 1 MHz, i.e., 1 tick equals 1 microsecond
    };
    // Create a timer instance
    ESP_ERROR_CHECK(gptimer_new_timer(&timer_config, &gptimer));

    static bool example_timer_on_alarm_cb(gptimer_handle_t timer, const gptimer_alarm_event_data_t *edata, void *user_ctx)
    {
        // General process for handling event callbacks:
        // 1. Retrieve user context data from user_ctx (passed in from gptimer_register_event_callbacks)
        // 2. Get alarm event data from edata, such as edata->count_value
        // 3. Perform user-defined operations
        // 4. Return whether a high-priority task was awakened during the above operations to notify the scheduler to switch tasks
        return false;
    }

    gptimer_alarm_config_t alarm_config = {
        .reload_count = 0,      // When the alarm event occurs, the timer will automatically reload to 0
        .alarm_count = 1000000, // Set the actual alarm period, since the resolution is 1us, 1000000 represents 1s
        .flags.auto_reload_on_alarm = true, // Enable auto-reload function
    };
    // Set the timer's alarm action
    ESP_ERROR_CHECK(gptimer_set_alarm_action(gptimer, &alarm_config));

    gptimer_event_callbacks_t cbs = {
        .on_alarm = example_timer_on_alarm_cb, // Call the user callback function when the alarm event occurs
    };
    // Register timer event callback functions, allowing user context to be carried
    ESP_ERROR_CHECK(gptimer_register_event_callbacks(gptimer, &cbs, NULL));
    // Enable the timer
    ESP_ERROR_CHECK(gptimer_enable(gptimer));
    // Start the timer
    ESP_ERROR_CHECK(gptimer_start(gptimer));

The `gptimer_set_alarm_action()` function is used to configure the timer's alarm action. When the timer count value reaches the specified alarm value, an alarm event will be triggered. Users can choose to automatically reload the preset count value when the alarm event occurs, thereby achieving periodic alarms.

Here are the necessary members of the `gptimer_alarm_config_t` structure and their functions. By configuring these parameters, users can flexibly control the timer's alarm behavior to meet different application needs.

- `gptimer_alarm_config_t::alarm_count` sets the target count value that triggers the alarm event. When the timer count value reaches this value, an alarm event will be triggered. When setting the alarm value, consider the counting direction of the timer. If the current count value has exceeded the alarm value, the alarm event will be triggered immediately.

- `gptimer_alarm_config_t::reload_count` sets the count value to be reloaded when the alarm event occurs. This configuration only takes effect when the `gptimer_alarm_config_t::flags::auto_reload_on_alarm` flag is `true`. The actual alarm period will be determined by `|alarm_count - reload_count|`. From a practical application perspective, it is not recommended to set the alarm period to less than 5us.

Note

Specifically, `gptimer_set_alarm_action(gptimer, NULL);` means disabling the timer's alarm function.

The `gptimer_register_event_callbacks()` function is used to register the timer event callback functions. When the timer triggers a specific event (such as an alarm event), the user-defined callback function will be called. Users can perform custom operations in the callback function, such as sending signals, to achieve more flexible event handling mechanisms. Since the callback function is executed in the interrupt context, avoid performing complex operations (including any operations that may cause blocking) in the callback function to avoid affecting the system's real-time performance. The `gptimer_register_event_callbacks()` function also allows users to pass a context pointer to access user-defined data in the callback function.

The supported event callback functions for GPTimer are as follows:

- `gptimer_alarm_cb_t` alarm event callback function, which has a corresponding data structure `gptimer_alarm_event_data_t` for passing alarm event-related data: - `gptimer_alarm_event_data_t::alarm_value` stores the alarm value, which is the target count value that triggers the alarm event. - `gptimer_alarm_event_data_t::count_value` stores the count value when entering the interrupt handler after the alarm occurs. This value may differ from the alarm value due to interrupt handler delays, and the count value may have been automatically reloaded when the alarm occurred.

Note

Be sure to register the callback function before calling `gptimer_enable()`, otherwise the timer event will not correctly trigger the interrupt service.

### Triggering One-Shot Alarm Events

Some application scenarios only require triggering a one-shot alarm interrupt. The following code shows how to set a one-shot alarm that triggers after 1 second:

    gptimer_handle_t gptimer = NULL;
    gptimer_config_t timer_config = {
        .clk_src = GPTIMER_CLK_SRC_DEFAULT, // Select the default clock source
        .direction = GPTIMER_COUNT_UP,      // Counting direction is up
        .resolution_hz = 1 * 1000 * 1000,   // Resolution is 1 MHz, i.e., 1 tick equals 1 microsecond
    };
    // Create a timer instance
    ESP_ERROR_CHECK(gptimer_new_timer(&timer_config, &gptimer));

    static bool example_timer_on_alarm_cb(gptimer_handle_t timer, const gptimer_alarm_event_data_t *edata, void *user_ctx)
    {
        // This is just a demonstration of how to stop the timer when the alarm occurs for the first time
        gptimer_stop(timer);
        // General process for handling event callbacks:
        // 1. Retrieve user context data from user_ctx (passed in from gptimer_register_event_callbacks)
        // 2. Get alarm event data from edata, such as edata->count_value
        // 3. Perform user-defined operations
        // 4. Return whether a high-priority task was awakened during the above operations to notify the scheduler to switch tasks
        return false;
    }

    gptimer_alarm_config_t alarm_config = {
        .alarm_count = 1000000, // Set the actual alarm period, since the resolution is 1us, 1000000 represents 1s
        .flags.auto_reload_on_alarm = false; // Disable auto-reload function
    };
    // Set the timer's alarm action
    ESP_ERROR_CHECK(gptimer_set_alarm_action(gptimer, &alarm_config));

    gptimer_event_callbacks_t cbs = {
        .on_alarm = example_timer_on_alarm_cb, // Call the user callback function when the alarm event occurs
    };
    // Register timer event callback functions, allowing user context to be carried
    ESP_ERROR_CHECK(gptimer_register_event_callbacks(gptimer, &cbs, NULL));
    // Enable the timer
    ESP_ERROR_CHECK(gptimer_enable(gptimer));
    // Start the timer
    ESP_ERROR_CHECK(gptimer_start(gptimer));

Unlike periodic alarms, the above code disables the auto-reload function when configuring the alarm behavior. This means that after the alarm event occurs, the timer will not automatically reload to the preset count value but will continue counting until it overflows. If you want the timer to stop immediately after the alarm, you can call `gptimer_stop()` in the callback function.

### Resource Recycling

When the timer is no longer needed, you should call the `gptimer_delete_timer()` function to release software and hardware resources. Before deleting, ensure that the timer is already stopped.

## Advanced Features

After understanding the basic usage, we can further explore more features of the GPTimer driver.

### Dynamic Alarm Value Update

The GPTimer driver supports dynamically updating the alarm value in the interrupt callback function by calling the `gptimer_set_alarm_action()` function, thereby implementing a monotonic software timer list. The following code shows how to reset the next alarm trigger time when the alarm event occurs:

    gptimer_handle_t gptimer = NULL;
    gptimer_config_t timer_config = {
        .clk_src = GPTIMER_CLK_SRC_DEFAULT, // Select the default clock source
        .direction = GPTIMER_COUNT_UP,      // Counting direction is up
        .resolution_hz = 1 * 1000 * 1000,   // Resolution is 1 MHz, i.e., 1 tick equals 1 microsecond
    };
    // Create a timer instance
    ESP_ERROR_CHECK(gptimer_new_timer(&timer_config, &gptimer));

    static bool example_timer_on_alarm_cb(gptimer_handle_t timer, const gptimer_alarm_event_data_t *edata, void *user_ctx)
    {
        gptimer_alarm_config_t alarm_config = {
            .alarm_count = edata->alarm_value + 1000000, // Next alarm in 1s from the current alarm
        };
        // Update the alarm value
        gptimer_set_alarm_action(timer, &alarm_config);
        return false;
    }

    gptimer_alarm_config_t alarm_config = {
        .alarm_count = 1000000, // Set the actual alarm period, since the resolution is 1us, 1000000 represents 1s
        .flags.auto_reload_on_alarm = false, // Disable auto-reload function
    };
    // Set the timer's alarm action
    ESP_ERROR_CHECK(gptimer_set_alarm_action(gptimer, &alarm_config));

    gptimer_event_callbacks_t cbs = {
        .on_alarm = example_timer_on_alarm_cb, // Call the user callback function when the alarm event occurs
    };
    // Register timer event callback functions, allowing user context to be carried
    ESP_ERROR_CHECK(gptimer_register_event_callbacks(gptimer, &cbs, NULL));
    // Enable the timer
    ESP_ERROR_CHECK(gptimer_enable(gptimer));
    // Start the timer
    ESP_ERROR_CHECK(gptimer_start(gptimer));

### GPTimer's ETM Events and Tasks

GPTimer can generate various events that can be connected to the ETM module. The event types are listed in `gptimer_etm_event_type_t`. Users can create an `ETM event` handle by calling `gptimer_new_etm_event()`. GPTimer also supports some tasks that can be triggered by other events and executed automatically. The task types are listed in `gptimer_etm_task_type_t`. Users can create an `ETM task` handle by calling `gptimer_new_etm_task()`.

For how to connect the timer events and tasks to the ETM channel, please refer to the ETM documentation.

### Power Management

When power management CONFIG_PM_ENABLE is enabled, the system may adjust or disable the clock source before entering sleep mode, causing the GPTimer to lose accuracy.

To prevent this, the GPTimer driver creates a power management lock internally. When the `gptimer_enable()` function is called, the lock is activated to ensure the system does not enter sleep mode, thus maintaining the timer's accuracy. To reduce power consumption, you can call the `gptimer_disable()` function to release the power management lock, allowing the system to enter sleep mode. However, this will stop the timer, so you need to restart the timer after waking up.

Besides disabling the clock source, the system can also power down the GPTimer before entering sleep mode to further reduce power consumption. To achieve this, set `gptimer_config_t::allow_pd` to `true`. Before the system enters sleep mode, the GPTimer register context will be backed up to memory and restored after the system wakes up. Note that enabling this option reduces power consumption but increases memory usage. Therefore, you need to balance power consumption and memory usage when using this feature.

### Thread Safety

The driver uses critical sections to ensure atomic operations on registers. Key members in the driver handle are also protected by critical sections. The driver's internal state machine uses atomic instructions to ensure thread safety, with state checks preventing certain invalid concurrent operations (e.g., conflicts between start and stop). Therefore, GPTimer driver APIs can be used in a multi-threaded environment without extra locking.

The following functions can also be used in an interrupt context:

- `gptimer_start()`

- `gptimer_stop()`

- `gptimer_get_raw_count()`

- `gptimer_set_raw_count()`

- `gptimer_get_captured_count()`

- `gptimer_set_alarm_action()`

### Cache Safety

When the file system performs Flash read/write operations, the system temporarily disables the Cache function to avoid errors when loading instructions and data from Flash. This causes the GPTimer interrupt handler to be unresponsive during this period, preventing the user callback function from executing in time. If you want the interrupt handler to run normally when the Cache is disabled, you can enable the CONFIG_GPTIMER_ISR_CACHE_SAFE option.

Note

Note that when this option is enabled, all interrupt callback functions and their context data must be placed in internal storage. This is because the system cannot load data and instructions from Flash when the Cache is disabled.

### Performance

To improve the real-time responsiveness of interrupt handling, the GPTimer driver provides the CONFIG_GPTIMER_ISR_HANDLER_IN_IRAM option. Once enabled, the interrupt handler is placed in internal RAM, reducing delays caused by potential cache misses when loading instructions from Flash.

Note

However, the user callback function and its context data called by the interrupt handler may still reside in Flash. Cache misses are still possible, so users must manually place the callback function and data in internal RAM, for example by using `IRAM_ATTR` and `DRAM_ATTR`.

As mentioned above, the GPTimer driver allows some functions to be called in an interrupt context. By enabling the CONFIG_GPTIMER_CTRL_FUNC_IN_IRAM option, these functions can also be placed in IRAM, which helps avoid performance loss caused by cache misses and allows them to be used when the Cache is disabled.

### Other Kconfig Options

- The CONFIG_GPTIMER_ENABLE_DEBUG_LOG option forces the GPTimer driver to enable all debug logs, regardless of the global log level settings. Enabling this option helps developers obtain more detailed log information during debugging, making it easier to locate and solve problems.

### Resource Consumption

Use the IDF Size tool to check the code and data consumption of the GPTimer driver. The following are the test conditions (using ESP32-C2 as an example):

- Compiler optimization level set to `-Os` to ensure minimal code size.

- Default log level set to `ESP_LOG_INFO` to balance debug information and performance.

- Disable the following driver optimization options:

    - CONFIG_GPTIMER_ISR_HANDLER_IN_IRAM - Do not place the interrupt handler in IRAM.

    - CONFIG_GPTIMER_CTRL_FUNC_IN_IRAM - Do not place control functions in IRAM.

    - CONFIG_GPTIMER_ISR_CACHE_SAFE - Do not enable Cache safety options.

Note that the following data are not exact values and are for reference only; they may differ on different chip models.

Component Layer | Total Size | DIRAM | .bss | .data | .text | Flash Code | .text | Flash Data | .rodata
--- | --- | --- | --- | --- | --- | --- | --- | --- | ---
soc | 8 | 0 | 0 | 0 | 0 | 0 | 0 | 8 | 8
hal | 206 | 0 | 0 | 0 | 0 | 206 | 206 | 0 | 0
driver | 4251 | 12 | 12 | 0 | 0 | 4046 | 4046 | 193 | 193

Additionally, each GPTimer handle dynamically allocates about `100` bytes of memory from the heap. If the `gptimer_config_t::flags::allow_pd` option is enabled, each timer will also consume approximately `30` extra bytes of memory during sleep to store the register context.

## Application Examples

- peripherals/timer_group/gptimer demonstrates how to use the general-purpose timer APIs on ESP SOC chips to generate periodic alarm events and trigger different alarm actions.

- peripherals/timer_group/wiegand_interface uses two timers (one in one-shot alarm mode and the other in periodic alarm mode) to trigger interrupts and change the GPIO output state in the alarm event callback function, simulating the output waveform of the Wiegand protocol.

- peripherals/timer_group/gptimer_capture_hc_sr04 demonstrates how to use the general-purpose timer and Event Task Matrix (ETM) to accurately capture timestamps of ultrasonic sensor events and convert them into distance information.

## API Reference

### GPTimer Driver APIs

#### Header File

- components/esp_driver_gptimer/include/driver/gptimer.h

- This header file can be included with:

  >     #include "driver/gptimer.h"

- This header file is a part of the API provided by the `esp_driver_gptimer` component. To declare that your component depends on `esp_driver_gptimer`, add the following to your CMakeLists.txt:

  >     REQUIRES esp_driver_gptimer

  > or

  >     PRIV_REQUIRES esp_driver_gptimer

#### 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

  Different from `gptimer_get_raw_count`, this function won't trigger a software capture event. It just returns the last captured count value. It's especially useful when the capture has already been triggered by an external event and you want to read the captured 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 -- [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 you can update new alarm action immediately in any 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. In this case, please also ensure the `gptimer_alarm_config_t` instance is placed in the static data section instead of in the read-only data section. e.g.: `static gptimer_alarm_config_t alarm_config = { ... };`

  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

  uint32_t allow_pd

    If set, driver allows the power domain to be powered off when system enters sleep mode. This can save power, but at the expense of more RAM being consumed to save register context.

  struct gptimer_config_t 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_CACHE_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 flags

    Alarm config flags

### GPTimer Driver Types

#### Header File

- components/esp_driver_gptimer/include/driver/gptimer_types.h

- This header file can be included with:

  >     #include "driver/gptimer_types.h"

- This header file is a part of the API provided by the `esp_driver_gptimer` component. To declare that your component depends on `esp_driver_gptimer`, add the following to your CMakeLists.txt:

  >     REQUIRES esp_driver_gptimer

  > or

  >     PRIV_REQUIRES esp_driver_gptimer

#### 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

### GPTimer HAL Types

#### Header File

- components/esp_hal_timg/include/hal/timer_types.h

- This header file can be included with:

  >     #include "hal/timer_types.h"

- This header file is a part of the API provided by the `esp_hal_timg` component. To declare that your component depends on `esp_hal_timg`, add the following to your CMakeLists.txt:

  >     REQUIRES esp_hal_timg

  > or

  >     PRIV_REQUIRES esp_hal_timg

#### 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

### GPTimer ETM APIs

#### Header File

- components/esp_driver_gptimer/include/driver/gptimer_etm.h

- This header file can be included with:

  >     #include "driver/gptimer_etm.h"

- This header file is a part of the API provided by the `esp_driver_gptimer` component. To declare that your component depends on `esp_driver_gptimer`, add the following to your CMakeLists.txt:

  >     REQUIRES esp_driver_gptimer

  > or

  >     PRIV_REQUIRES esp_driver_gptimer

#### 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

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