Touch Element

[中文]

Overview

The Touch Element Library is a highly abstracted element library designed on the basis of the touch sensor driver. The library provides a unified and user-friendly software interface to quickly build capacitive touch sensor applications.

Warning

The Touch Element Library currently is still based on the legacy touch driver. Please refer to the new driver of Capacitive Touch Sensor if you don't need the Touch Element Library.

Architecture

The Touch Element library configures touch sensor peripherals via the touch sensor driver. However, some necessary hardware parameters should be passed to touch_element_install() and will be configured automatically only after calling touch_element_start(). This sequential order is essential because configuring these parameters has a significant impact on the run-time system. Therefore, they must be configured after calling the start function to ensure the system functions properly.

These parameters include touch channel threshold, driver-level of waterproof shield sensor, etc. The Touch Element library sets the touch sensor interrupt and the esp_timer routine up, and the hardware information of the touch sensor (channel state, channel number) will be obtained in the touch sensor interrupt service routine. When the specified channel event occurs, the hardware information is passed to the esp_timer callback routine, which then dispatches the touch sensor channel information to the touch elements (such as button, slider, etc.). The library then runs a specified algorithm to update the touch element's state or calculate its position and dispatches the result accordingly.

So when using the Touch Element library, you are relieved from the implementation details of the touch sensor peripheral. The library handles most of the hardware information and passes the more meaningful messages to the event handler routine.

The workflow of the Touch Element library is illustrated in the picture below.

../../_images/te_architecture.svg

Touch Element architecture

The features in relation to the Touch Element library in ESP32-S2 are given in the table below.

Features

ESP32S2

Touch Element waterproof

✔

Touch Element button

✔

Touch Element slider

✔

Touch Element matrix button

✔

Peripheral

ESP32-S2 integrates one touch sensor peripheral with several physical channels.

  • 14 physical capacitive touch channels

  • Timer or software FSM trigger mode

  • Up to 5 kinds of interrupt (Upper threshold and lower threshold interrupt, measure one channel finish and measure all channels finish interrupt, measurement timeout interrupt)

  • Sleep mode wakeup source

  • Hardware internal de-noise

  • Hardware filter

  • Hardware waterproof sensor

  • Hardware proximity sensor

The channels are located as follows:

Channel

ESP32-S2

Channel 0

GPIO 0 (reserved)

Channel 1

GPIO 1

Channel 2

GPIO 2

Channel 3

GPIO 3

Channel 4

GPIO 4

Channel 5

GPIO 5

Channel 6

GPIO 6

Channel 7

GPIO 7

Channel 8

GPIO 8

Channel 9

GPIO 9

Channel 10

GPIO 10

Channel 11

GPIO 11

Channel 12

GPIO 12

Channel 13

GPIO 13

Channel 14

GPIO 14

The channels are located as follows:

Channel

ESP32-S2

Channel 0

GPIO 0 (effective)

Channel 1

GPIO 1

Channel 2

GPIO 2

Channel 3

GPIO 3

Channel 4

GPIO 4

Channel 5

GPIO 5

Channel 6

GPIO 6

Channel 7

GPIO 7

Channel 8

GPIO 8

Channel 9

GPIO 9

Terminology

The terms used in relation to the Touch Element library are given below.

Term

Definition

Touch sensor

Touch sensor peripheral inside the chip

Touch channel

Touch sensor channels inside the touch sensor peripheral

Touch pad

Off-chip physical solder pad, generally inside the PCB

De-noise channel

Internal de-noise channel, which is always Channel 0 and is reserved

Shield sensor

One of the waterproof sensors for detecting droplets in small areas and compensating for the influence of water drops on measurements

Guard sensor

One of the waterproof sensors for detecting extensive wading and to temporarily disable the touch sensor

Shield channel

The channel that waterproof shield sensor connected to, which is always Channel 14

Guard channel

The channel that waterproof guard sensor connected to

Shield pad

Off-chip physical solder pad, generally is grids, and is connected to shield the sensor

Guard pad

Off-chip physical solder pad, usually a ring, and is connected to the guard sensor
../../_images/te_component.svg

Touch sensor application system components

Touch Sensor Signal

Each touch sensor is able to provide the following types of signals:

  • Raw: The Raw signal is the unfiltered signal from the touch sensor.

  • Smooth: The Smooth signal is a filtered version of the Raw signal via an internal hardware filter.

  • Benchmark: The Benchmark signal is also a filtered signal that filters out extremely low-frequency noise.

All of these signals can be obtained using touch sensor driver API.

../../_images/te_signal.png

Touch sensor signals

Touch Sensor Signal Threshold

The Touch Sensor Threshold value is a configurable threshold value used to determine when a touch sensor is touched or not. When the difference between the Smooth signal and the Benchmark signal becomes greater than the threshold value (i.e., (smooth - benchmark) > threshold), the touch channel's state will be changed and a touch interrupt will be triggered simultaneously.

../../_images/te_threshold.svg

Touch sensor signal threshold

Sensitivity

Important performance parameter of the touch sensor, the larger it is, the better touch the sensor performs. It could be calculated by the format below:

\[Sensitivity = \frac{Signal_{press} - Signal_{release}}{Signal_{release}} = \frac{Signal_{delta}}{Signal_{benchmark}}\]

Waterproof

Waterproof is the hardware feature of a touch sensor which has a guard sensor and shield sensor (always connect to Channel 14) that has the ability to resist a degree of influence of water drop and detect the water stream.

Touch Button

The touch button consumes one channel of the touch sensor, and it looks like as the picture below:

../../_images/te_button.svg

Touch button

Touch Slider

The touch slider consumes several channels (at least three channels) of the touch sensor, the more channels consumed, the higher resolution and accuracy position it performs. The touch slider looks like as the picture below:

../../_images/te_slider.svg

Touch slider

Touch Matrix

The touch matrix button consumes several channels (at least 2 + 2 = 4 channels), and it gives a solution to use fewer channels and get more buttons. ESP32-S2 supports up to 49 buttons. The touch matrix button looks like as the picture below:

../../_images/te_matrix.svg

Touch matrix

Touch Element Library Usage

Using this library should follow the initialization flow below:

  1. To initialize the Touch Element library by calling touch_element_install().

  2. To initialize touch elements (button/slider etc) by calling touch_xxxx_install().

  3. To create a new element instance by calling touch_xxxx_create().

  4. To subscribe events by calling touch_xxxx_subscribe_event().

  5. To choose a dispatch method by calling touch_xxxx_set_dispatch_method() that tells the library how to notify you while the subscribed event occurs.

  6. If dispatch by callback, call touch_xxxx_set_callback() to set the event handler function.

  7. To start the Touch Element library by calling touch_element_start().

  8. If dispatch by callback, the callback will be called by the driver core when an event happens, no need to do anything; If dispatch by event task, create an event task and call touch_element_message_receive() to obtain messages in a loop.

  9. (Optional) If you want to suspend the Touch Element run-time system or for some reason that could not obtain the touch element message, touch_element_stop() should be called to suspend the Touch Element system and then resume it by calling touch_element_start() again.

In code, the flow above may look like as follows:

static touch_xxx_handle_t element_handle; //Declare a touch element handle

//Define the subscribed event handler
void event_handler(touch_xxx_handle_t out_handle, touch_xxx_message_t out_message, void *arg)
{
    //Event handler logic
}

void app_main()
{
    //Using the default initializer to config Touch Element library
    touch_elem_global_config_t global_config = TOUCH_ELEM_GLOBAL_DEFAULT_CONFIG();
    touch_element_install(&global_config);

    //Using the default initializer to config Touch elements
    touch_xxx_global_config_t elem_global_config = TOUCH_XXXX_GLOBAL_DEFAULT_CONFIG();
    touch_xxx_install(&elem_global_config);

    //Create a new instance
    touch_xxx_config_t element_config = {
        ...
        ...
    };
    touch_xxx_create(&element_config, &element_handle);

    //Subscribe the specified events by using the event mask
    touch_xxx_subscribe_event(element_handle, TOUCH_ELEM_EVENT_ON_PRESS | TOUCH_ELEM_EVENT_ON_RELEASE, NULL);

    //Choose CALLBACK as the dispatch method
    touch_xxx_set_dispatch_method(element_handle, TOUCH_ELEM_DISP_CALLBACK);

    //Register the callback routine
    touch_xxx_set_callback(element_handle, event_handler);

    //Start Touch Element library processing
    touch_element_start();
}

Initialization

  1. To initialize the Touch Element library, you have to configure the touch sensor peripheral and Touch Element library by calling touch_element_install() with touch_elem_global_config_t, the default initializer is available in TOUCH_ELEM_GLOBAL_DEFAULT_CONFIG() and this default configuration is suitable for the most general application scene, and it is suggested not to change the default configuration before fully understanding Touch Sensor peripheral because some changes might bring several impacts to the system.

  2. To initialize the specified element, all the elements will not work before its constructor touch_xxxx_install() is called so as to save memory, so you have to call the constructor of each used touch element respectively, to set up the specified element.

Touch Element Instance Startup

  1. To create a new touch element instance, call touch_xxxx_create(), select a channel, and provide its Sensitivity value for the new element instance.

  2. To subscribe to events, call touch_xxxx_subscribe_event(). The Touch Element library offers several events, and the event mask is available in components/touch_element/include/touch_element/touch_element.h. You can use these event masks to subscribe to specific events individually or combine them to subscribe to multiple events.

  3. To configure the dispatch method, use touch_xxxx_set_dispatch_method(). The Touch Element library provides two dispatch methods: TOUCH_ELEM_DISP_EVENT and TOUCH_ELEM_DISP_CALLBACK. These methods allow you to obtain the touch element message and handle it using different approaches.

Events Processing

If TOUCH_ELEM_DISP_EVENT dispatch method is configured, you need to start up an event handler task to obtain the touch element message, all the elements' raw message could be obtained by calling touch_element_message_receive(), then extract the element-class-specific message by calling the corresponding message decoder with touch_xxxx_get_message() to get the touch element's extracted message; If TOUCH_ELEM_DISP_CALLBACK dispatch method is configured, you need to pass an event handler by calling touch_xxxx_set_callback() before the touch element starts working, all the element's extracted message will be passed to the event handler function.

Warning

Since the event handler function runs on the core of the element library, i.e., in the esp_timer callback routine, please avoid performing operations that may cause blocking or delays, such as calling vTaskDelay().

In code, the events handle procedure may look like as follows:

/* ---------------------------------------------- TOUCH_ELEM_DISP_EVENT ----------------------------------------------- */
void element_handler_task(void *arg)
{
    touch_elem_message_t element_message;
    while(1) {
        if (touch_element_message_receive(&element_message, Timeout) == ESP_OK) {
            const touch_xxxx_message_t *extracted_message = touch_xxxx_get_message(&element_message); //Decode message
            ... //Event handler logic
        }
    }
}
void app_main()
{
    ...

    touch_xxxx_set_dispatch_method(element_handle, TOUCH_ELEM_DISP_EVENT);  //Set TOUCH_ELEM_DISP_EVENT as the dispatch method
    xTaskCreate(&element_handler_task, "element_handler_task", 2048, NULL, 5, NULL);  //Create a handler task

    ...
}
/* -------------------------------------------------------------------------------------------------------------- */

...
/* ---------------------------------------------- TOUCH_ELEM_DISP_CALLBACK ----------------------------------------------- */
void element_handler(touch_xxxx_handle_t out_handle, touch_xxxx_message_t out_message, void *arg)
{
    //Event handler logic
}

void app_main()
{
    ...

    touch_xxxx_set_dispatch_method(element_handle, TOUCH_ELEM_DISP_CALLBACK);  //Set TOUCH_ELEM_DISP_CALLBACK as the dispatch method
    touch_xxxx_set_callback(element_handle, element_handler);  //Register an event handler function

    ...
}
/* -------------------------------------------------------------------------------------------------------------- */

Waterproof Usage

  1. The waterproof shield sensor is always-on after Touch Element waterproof is initialized, however, the waterproof guard sensor is optional, hence if the you do not need the guard sensor, TOUCH_WATERPROOF_GUARD_NOUSE has to be passed to touch_element_waterproof_install() by the configuration struct.

  2. To associate the touch element with the guard sensor, pass the touch element's handle to the Touch Element waterproof's masked list by calling touch_element_waterproof_add(). By associating a touch element with the Guard sensor, the touch element will be disabled when the guard sensor is triggered by a stream of water so as to protect the touch element.

The Touch Element Waterproof example is available in peripherals/touch_sensor/touch_element/touch_element_waterproof directory.

In code, the waterproof configuration may look as follows:

void app_main()
{
    ...

    touch_xxxx_install();                 //Initialize instance (button, slider, etc)
    touch_xxxx_create(&element_handle);  //Create a new Touch element

    ...

    touch_element_waterproof_install();              //Initialize Touch Element waterproof
    touch_element_waterproof_add(element_handle);   //Let an element associate with the guard sensor

    ...
}

Wakeup from Light/Deep-sleep Mode

Only Touch Button can be configured as a wake-up source.

Light- or Deep-sleep modes are both supported to be wakened up by a touch sensor. For the Light-sleep mode, any installed touch button can wake it up. But only the sleep button can wake up from Deep-sleep mode, and the touch sensor will do a calibration immediately, the reference value will be calibrated to a wrong value if our finger does not remove timely. Though the wrong reference value recovers after the finger removes away and has no effect on the driver logic, if you do not want to see a wrong reference value while waking up from Deep-sleep mode, you can call touch_element_sleep_enable_wakeup_calibration() to disable the wakeup calibration.

The Touch Element Wakeup example is available in system/light_sleep directory.

void app_main()
{
    ...
    touch_element_install();
    touch_button_install();                 //Initialize the touch button
    touch_button_create(&element_handle);  //Create a new Touch element

    ...

    // ESP_ERROR_CHECK(touch_element_enable_light_sleep(&sleep_config));
    ESP_ERROR_CHECK(touch_element_enable_deep_sleep(button_handle[0], &sleep_config));
    // ESP_ERROR_CHECK(touch_element_sleep_enable_wakeup_calibration(button_handle[0], false)); // (optional) Disable wakeup calibration to prevent updating the benchmark to a wrong value

    touch_element_start();

    ...
}

Application Examples

API Reference - Touch Element Core

Header File

  • components/touch_element/include/touch_element/touch_element.h

  • This header file can be included with:

    #include "touch_element/touch_element.h"

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

    REQUIRES touch_element

    or

    PRIV_REQUIRES touch_element

Functions

esp_err_t touch_element_install(const touch_elem_global_config_t *global_config)

Touch element processing initialization.

Note

To reinitialize the touch element object, call touch_element_uninstall() first

Parameters

global_config -- [in] Global initialization configuration structure

Returns

  • ESP_OK: Successfully initialized

  • ESP_ERR_INVALID_ARG: Invalid argument

  • ESP_ERR_NO_MEM: Insufficient memory

  • ESP_ERR_INVALID_STATE: Touch element is already initialized

  • Others: Unknown touch driver layer or lower layer error

esp_err_t touch_element_start(void)

Touch element processing start.

This function starts the touch element processing system

Note

This function must only be called after all the touch element instances finished creating

Returns

  • ESP_OK: Successfully started to process

  • Others: Unknown touch driver layer or lower layer error

esp_err_t touch_element_stop(void)

Touch element processing stop.

This function stops the touch element processing system

Note

This function must be called before changing the system (hardware, software) parameters

Returns

  • ESP_OK: Successfully stopped to process

  • Others: Unknown touch driver layer or lower layer error

void touch_element_uninstall(void)

Release resources allocated using touch_element_install.

esp_err_t touch_element_message_receive(touch_elem_message_t *element_message, uint32_t ticks_to_wait)

Get current event message of touch element instance.

This function will receive the touch element message (handle, event type, etc...) from te_event_give(). It will block until a touch element event or a timeout occurs.

Parameters

  • element_message -- [out] Touch element event message structure

  • ticks_to_wait -- [in] Number of FreeRTOS ticks to block for waiting event

Returns

  • ESP_OK: Successfully received touch element event

  • ESP_ERR_INVALID_STATE: Touch element library is not initialized

  • ESP_ERR_INVALID_ARG: element_message is null

  • ESP_ERR_TIMEOUT: Timed out waiting for event

esp_err_t touch_element_waterproof_install(const touch_elem_waterproof_config_t *waterproof_config)

Touch element waterproof initialization.

This function enables the hardware waterproof, then touch element system uses Shield-Sensor and Guard-Sensor to mitigate the influence of water-drop and water-stream.

Note

If the waterproof function is used, Shield-Sensor can not be disabled and it will use channel 14 as it's internal channel. Hence, the user can not use channel 14 for another propose. And the Guard-Sensor is not necessary since it is optional.

Note

Shield-Sensor: It always uses channel 14 as the shield channel, so user must connect the channel 14 and Shield-Layer in PCB since it will generate a synchronous signal automatically

Note

Guard-Sensor: This function is optional. If used, the user must connect the guard channel and Guard-Ring in PCB. Any channels user wants to protect should be added into Guard-Ring in PCB.

Parameters

waterproof_config -- [in] Waterproof configuration

Returns

  • ESP_OK: Successfully initialized

  • ESP_ERR_INVALID_STATE: Touch element library is not initialized

  • ESP_ERR_INVALID_ARG: waterproof_config is null or invalid Guard-Sensor channel

  • ESP_ERR_NO_MEM: Insufficient memory

void touch_element_waterproof_uninstall(void)

Release resources allocated using touch_element_waterproof_install()

esp_err_t touch_element_waterproof_add(touch_elem_handle_t element_handle)

Add a masked handle to protect while Guard-Sensor has been triggered.

This function will add an application handle (button, slider, etc...) as a masked handle. While Guard-Sensor has been triggered, waterproof function will start working and lock the application internal state. While the influence of water is reduced, the application will be unlock and reset into IDLE state.

Note

The waterproof protection logic must follow the real circuit in PCB, it means that all of the channels inside the input handle must be inside the Guard-Ring in real circuit.

Parameters

element_handle -- [in] Touch element instance handle

Returns

  • ESP_OK: Successfully added a masked handle

  • ESP_ERR_INVALID_STATE: Waterproof is not initialized

  • ESP_ERR_INVALID_ARG: element_handle is null

esp_err_t touch_element_waterproof_remove(touch_elem_handle_t element_handle)

Remove a masked handle to protect.

This function will remove an application handle from masked handle table.

Parameters

element_handle -- [in] Touch element instance handle

Returns

  • ESP_OK: Successfully removed a masked handle

  • ESP_ERR_INVALID_STATE: Waterproof is not initialized

  • ESP_ERR_INVALID_ARG: element_handle is null

  • ESP_ERR_NOT_FOUND: Failed to search element_handle from waterproof mask_handle list

esp_err_t touch_element_enable_light_sleep(const touch_elem_sleep_config_t *sleep_config)

Touch element light sleep initialization.

Note

It should be called after touch button element installed. Any of installed touch element can wake up from the light sleep

Parameters

sleep_config -- [in] Sleep configurations, set NULL to use default config

Returns

  • ESP_OK: Successfully initialized touch sleep

  • ESP_ERR_INVALID_STATE: Touch element is not installed or touch sleep has been installed

  • ESP_ERR_INVALID_ARG: inputted argument is NULL

  • ESP_ERR_NO_MEM: no memory for touch sleep struct

  • ESP_ERR_NOT_SUPPORTED: inputted wakeup_elem_handle is not touch_button_handle_t type, currently only touch_button_handle_t supported

esp_err_t touch_element_disable_light_sleep(void)

Release the resources that allocated by touch_element_enable_deep_sleep()

This function will also disable the touch sensor to wake up the device

Returns

  • ESP_OK: uninstall success

  • ESP_ERR_INVALID_STATE: touch sleep has not been installed

esp_err_t touch_element_enable_deep_sleep(touch_elem_handle_t wakeup_elem_handle, const touch_elem_sleep_config_t *sleep_config)

Touch element deep sleep initialization.

This function will enable the device wake-up from deep sleep or light sleep by touch sensor

Note

It should be called after touch button element installed. Only one touch button can be registered as the deep sleep wake-up button

Parameters

  • wakeup_elem_handle -- [in] Touch element instance handle for waking up the device, only support button element

  • sleep_config -- [in] Sleep configurations, set NULL to use default config

Returns

  • ESP_OK: Successfully initialized touch sleep

  • ESP_ERR_INVALID_STATE: Touch element is not installed or touch sleep has been installed

  • ESP_ERR_INVALID_ARG: inputted argument is NULL

  • ESP_ERR_NO_MEM: no memory for touch sleep struct

  • ESP_ERR_NOT_SUPPORTED: inputted wakeup_elem_handle is not touch_button_handle_t type, currently only touch_button_handle_t supported

esp_err_t touch_element_disable_deep_sleep(void)

Release the resources that allocated by touch_element_enable_deep_sleep()

This function will also disable the touch sensor to wake up the device

Returns

  • ESP_OK: uninstall success

  • ESP_ERR_INVALID_STATE: touch sleep has not been installed

esp_err_t touch_element_sleep_enable_wakeup_calibration(touch_elem_handle_t element_handle, bool en)

Touch element wake up calibrations.

This function will also disable the touch sensor to wake up the device

Returns

  • ESP_OK: uninstall success

  • ESP_ERR_INVALID_STATE: touch sleep has not been installed

Structures

struct touch_elem_sw_config_t

Touch element software configuration.

Public Members

float waterproof_threshold_divider

Waterproof guard channel threshold divider.

uint8_t processing_period

Processing period(ms)

uint8_t intr_message_size

Interrupt message queue size.

uint8_t event_message_size

Event message queue size.

struct touch_elem_hw_config_t

Touch element hardware configuration.

Public Members

touch_high_volt_t upper_voltage

Touch sensor channel upper charge voltage.

touch_volt_atten_t voltage_attenuation

Touch sensor channel upper charge voltage attenuation (Diff voltage is upper - attenuation - lower)

touch_low_volt_t lower_voltage

Touch sensor channel lower charge voltage.

touch_pad_conn_type_t suspend_channel_polarity

Suspend channel polarity (High Impedance State or GND)

touch_pad_denoise_grade_t denoise_level

Internal de-noise level.

touch_pad_denoise_cap_t denoise_equivalent_cap

Internal de-noise channel (Touch channel 0) equivalent capacitance.

touch_smooth_mode_t smooth_filter_mode

Smooth value filter mode (This only apply to touch_pad_filter_read_smooth())

touch_filter_mode_t benchmark_filter_mode

Benchmark filter mode.

uint16_t sample_count

The count of sample in each measurement of touch sensor.

uint16_t sleep_cycle

The cycle (RTC slow clock) of sleep.

uint8_t benchmark_debounce_count

Benchmark debounce count.

uint8_t benchmark_calibration_threshold

Benchmark calibration threshold.

uint8_t benchmark_jitter_step

Benchmark jitter filter step (This only works at while benchmark filter mode is jitter filter)

struct touch_elem_global_config_t

Touch element global configuration passed to touch_element_install.

Public Members

touch_elem_hw_config_t hardware

Hardware configuration.

touch_elem_sw_config_t software

Software configuration.

struct touch_elem_waterproof_config_t

Touch element waterproof configuration passed to touch_element_waterproof_install.

Public Members

touch_pad_t guard_channel

Waterproof Guard-Sensor channel number (index)

float guard_sensitivity

Waterproof Guard-Sensor sensitivity.

struct touch_elem_sleep_config_t

Touch element sleep configuration passed to touch_element_enable_light_sleep or touch_element_enable_deep_sleep.

Public Members

uint16_t sample_count

scan times in every measurement, normally equal to the 'sample_count' field in 'touch_elem_hw_config_t'.

uint16_t sleep_cycle

sleep_cycle decide the interval between two measurements， t_sleep = sleep_cycle / (RTC_SLOW_CLK frequency), normally equal to the 'sleep_cycle' field in 'touch_elem_hw_config_t'.

struct touch_elem_message_t

Touch element event message type from touch_element_message_receive()

Public Members

touch_elem_handle_t handle

Touch element handle.

touch_elem_type_t element_type

Touch element type.

void *arg

User input argument.

uint8_t child_msg[8]

Encoded message.

Macros

TOUCH_ELEM_GLOBAL_DEFAULT_CONFIG()
TOUCH_ELEM_EVENT_NONE

None event.

TOUCH_ELEM_EVENT_ON_PRESS

On Press event.

TOUCH_ELEM_EVENT_ON_RELEASE

On Release event.

TOUCH_ELEM_EVENT_ON_LONGPRESS

On LongPress event.

TOUCH_ELEM_EVENT_ON_CALCULATION

On Calculation event.

TOUCH_WATERPROOF_GUARD_NOUSE

Waterproof no use guard sensor.

Type Definitions

typedef void *touch_elem_handle_t

Touch element handle type.

typedef uint32_t touch_elem_event_t

Touch element event type.

Enumerations

enum touch_elem_type_t

Touch element handle type.

Values:

enumerator TOUCH_ELEM_TYPE_BUTTON

Touch element button.

enumerator TOUCH_ELEM_TYPE_SLIDER

Touch element slider.

enumerator TOUCH_ELEM_TYPE_MATRIX

Touch element matrix button.

enum touch_elem_dispatch_t

Touch element event dispatch methods (event queue/callback)

Values:

enumerator TOUCH_ELEM_DISP_EVENT

Event queue dispatch.

enumerator TOUCH_ELEM_DISP_CALLBACK

Callback dispatch.

enumerator TOUCH_ELEM_DISP_MAX

API Reference - Touch Button

Header File

  • components/touch_element/include/touch_element/touch_button.h

  • This header file can be included with:

    #include "touch_element/touch_button.h"

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

    REQUIRES touch_element

    or

    PRIV_REQUIRES touch_element

Functions

esp_err_t touch_button_install(const touch_button_global_config_t *global_config)

Touch Button initialize.

This function initializes touch button global and acts on all touch button instances.

Parameters

global_config -- [in] Button object initialization configuration

Returns

  • ESP_OK: Successfully initialized touch button

  • ESP_ERR_INVALID_STATE: Touch element library was not initialized

  • ESP_ERR_INVALID_ARG: button_init is NULL

  • ESP_ERR_NO_MEM: Insufficient memory

void touch_button_uninstall(void)

Release resources allocated using touch_button_install()

esp_err_t touch_button_create(const touch_button_config_t *button_config, touch_button_handle_t *button_handle)

Create a new touch button instance.

Note

The sensitivity has to be explored in experiments, Sensitivity = (Raw(touch) - Raw(release)) / Raw(release) * 100%

Parameters

  • button_config -- [in] Button configuration

  • button_handle -- [out] Button handle

Returns

  • ESP_OK: Successfully create touch button

  • ESP_ERR_INVALID_STATE: Touch button driver was not initialized

  • ESP_ERR_NO_MEM: Insufficient memory

  • ESP_ERR_INVALID_ARG: Invalid configuration struct or arguments is NULL

esp_err_t touch_button_delete(touch_button_handle_t button_handle)

Release resources allocated using touch_button_create()

Parameters

button_handle -- [in] Button handle

Returns

  • ESP_OK: Successfully released resources

  • ESP_ERR_INVALID_STATE: Touch button driver was not initialized

  • ESP_ERR_INVALID_ARG: button_handle is null

  • ESP_ERR_NOT_FOUND: Input handle is not a button handle

esp_err_t touch_button_subscribe_event(touch_button_handle_t button_handle, uint32_t event_mask, void *arg)

Touch button subscribes event.

This function uses event mask to subscribe to touch button events, once one of the subscribed events occurs, the event message could be retrieved by calling touch_element_message_receive() or input callback routine.

Note

Touch button only support three kind of event masks, they are TOUCH_ELEM_EVENT_ON_PRESS, TOUCH_ELEM_EVENT_ON_RELEASE, TOUCH_ELEM_EVENT_ON_LONGPRESS. You can use those event masks in any combination to achieve the desired effect.

Parameters

  • button_handle -- [in] Button handle

  • event_mask -- [in] Button subscription event mask

  • arg -- [in] User input argument

Returns

  • ESP_OK: Successfully subscribed touch button event

  • ESP_ERR_INVALID_STATE: Touch button driver was not initialized

  • ESP_ERR_INVALID_ARG: button_handle is null or event is not supported

esp_err_t touch_button_set_dispatch_method(touch_button_handle_t button_handle, touch_elem_dispatch_t dispatch_method)

Touch button set dispatch method.

This function sets a dispatch method that the driver core will use this method as the event notification method.

Parameters

  • button_handle -- [in] Button handle

  • dispatch_method -- [in] Dispatch method (By callback/event)

Returns

  • ESP_OK: Successfully set dispatch method

  • ESP_ERR_INVALID_STATE: Touch button driver was not initialized

  • ESP_ERR_INVALID_ARG: button_handle is null or dispatch_method is invalid

esp_err_t touch_button_set_callback(touch_button_handle_t button_handle, touch_button_callback_t button_callback)

Touch button set callback.

This function sets a callback routine into touch element driver core, when the subscribed events occur, the callback routine will be called.

Note

Button message will be passed from the callback function and it will be destroyed when the callback function return.

Warning

Since this input callback routine runs on driver core (esp-timer callback routine), it should not do something that attempts to Block, such as calling vTaskDelay().

Parameters

  • button_handle -- [in] Button handle

  • button_callback -- [in] User input callback

Returns

  • ESP_OK: Successfully set callback

  • ESP_ERR_INVALID_STATE: Touch button driver was not initialized

  • ESP_ERR_INVALID_ARG: button_handle or button_callback is null

esp_err_t touch_button_set_longpress(touch_button_handle_t button_handle, uint32_t threshold_time)

Touch button set long press trigger time.

This function sets the threshold time (ms) for a long press event. If a button is pressed and held for a period of time that exceeds the threshold time, a long press event is triggered.

Parameters

  • button_handle -- [in] Button handle

  • threshold_time -- [in] Threshold time (ms) of long press event occur

Returns

  • ESP_OK: Successfully set the threshold time of long press event

  • ESP_ERR_INVALID_STATE: Touch button driver was not initialized

  • ESP_ERR_INVALID_ARG: button_handle is null or time (ms) is not lager than 0

const touch_button_message_t *touch_button_get_message(const touch_elem_message_t *element_message)

Touch button get message.

This function decodes the element message from touch_element_message_receive() and return a button message pointer.

Parameters

element_message -- [in] element message

Returns

Touch button message pointer

Structures

struct touch_button_global_config_t

Button initialization configuration passed to touch_button_install.

Public Members

float threshold_divider

Button channel threshold divider.

uint32_t default_lp_time

Button default LongPress event time (ms)

struct touch_button_config_t

Button configuration (for new instance) passed to touch_button_create()

Public Members

touch_pad_t channel_num

Button channel number (index)

float channel_sens

Button channel sensitivity.

struct touch_button_message_t

Button message type.

Public Members

touch_button_event_t event

Button event.

Macros

TOUCH_BUTTON_GLOBAL_DEFAULT_CONFIG()

Type Definitions

typedef touch_elem_handle_t touch_button_handle_t

Button handle.

typedef void (*touch_button_callback_t)(touch_button_handle_t, touch_button_message_t*, void*)

Button callback type.

Enumerations

enum touch_button_event_t

Button event type.

Values:

enumerator TOUCH_BUTTON_EVT_ON_PRESS

Button Press event.

enumerator TOUCH_BUTTON_EVT_ON_RELEASE

Button Release event.

enumerator TOUCH_BUTTON_EVT_ON_LONGPRESS

Button LongPress event.

enumerator TOUCH_BUTTON_EVT_MAX

API Reference - Touch Slider

Header File

  • components/touch_element/include/touch_element/touch_slider.h

  • This header file can be included with:

    #include "touch_element/touch_slider.h"

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

    REQUIRES touch_element

    or

    PRIV_REQUIRES touch_element

Functions

esp_err_t touch_slider_install(const touch_slider_global_config_t *global_config)

Touch slider initialize.

This function initializes touch slider object and acts on all touch slider instances.

Parameters

global_config -- [in] Touch slider global initialization configuration

Returns

  • ESP_OK: Successfully initialized touch slider

  • ESP_ERR_INVALID_STATE: Touch element library was not initialized

  • ESP_ERR_INVALID_ARG: slider_init is NULL

  • ESP_ERR_NO_MEM: Insufficient memory

void touch_slider_uninstall(void)

Release resources allocated using touch_slider_install()

esp_err_t touch_slider_create(const touch_slider_config_t *slider_config, touch_slider_handle_t *slider_handle)

Create a new touch slider instance.

Note

The index of Channel array and sensitivity array must be one-one correspondence

Parameters

  • slider_config -- [in] Slider configuration

  • slider_handle -- [out] Slider handle

Returns

  • ESP_OK: Successfully create touch slider

  • ESP_ERR_INVALID_STATE: Touch slider driver was not initialized

  • ESP_ERR_INVALID_ARG: Invalid configuration struct or arguments is NULL

  • ESP_ERR_NO_MEM: Insufficient memory

esp_err_t touch_slider_delete(touch_slider_handle_t slider_handle)

Release resources allocated using touch_slider_create.

Parameters

slider_handle -- [in] Slider handle

Returns

  • ESP_OK: Successfully released resources

  • ESP_ERR_INVALID_STATE: Touch slider driver was not initialized

  • ESP_ERR_INVALID_ARG: slider_handle is null

  • ESP_ERR_NOT_FOUND: Input handle is not a slider handle

esp_err_t touch_slider_subscribe_event(touch_slider_handle_t slider_handle, uint32_t event_mask, void *arg)

Touch slider subscribes event.

This function uses event mask to subscribe to touch slider events, once one of the subscribed events occurs, the event message could be retrieved by calling touch_element_message_receive() or input callback routine.

Note

Touch slider only support three kind of event masks, they are TOUCH_ELEM_EVENT_ON_PRESS, TOUCH_ELEM_EVENT_ON_RELEASE. You can use those event masks in any combination to achieve the desired effect.

Parameters

  • slider_handle -- [in] Slider handle

  • event_mask -- [in] Slider subscription event mask

  • arg -- [in] User input argument

Returns

  • ESP_OK: Successfully subscribed touch slider event

  • ESP_ERR_INVALID_STATE: Touch slider driver was not initialized

  • ESP_ERR_INVALID_ARG: slider_handle is null or event is not supported

esp_err_t touch_slider_set_dispatch_method(touch_slider_handle_t slider_handle, touch_elem_dispatch_t dispatch_method)

Touch slider set dispatch method.

This function sets a dispatch method that the driver core will use this method as the event notification method.

Parameters

  • slider_handle -- [in] Slider handle

  • dispatch_method -- [in] Dispatch method (By callback/event)

Returns

  • ESP_OK: Successfully set dispatch method

  • ESP_ERR_INVALID_STATE: Touch slider driver was not initialized

  • ESP_ERR_INVALID_ARG: slider_handle is null or dispatch_method is invalid

esp_err_t touch_slider_set_callback(touch_slider_handle_t slider_handle, touch_slider_callback_t slider_callback)

Touch slider set callback.

This function sets a callback routine into touch element driver core, when the subscribed events occur, the callback routine will be called.

Note

Slider message will be passed from the callback function and it will be destroyed when the callback function return.

Warning

Since this input callback routine runs on driver core (esp-timer callback routine), it should not do something that attempts to Block, such as calling vTaskDelay().

Parameters

  • slider_handle -- [in] Slider handle

  • slider_callback -- [in] User input callback

Returns

  • ESP_OK: Successfully set callback

  • ESP_ERR_INVALID_STATE: Touch slider driver was not initialized

  • ESP_ERR_INVALID_ARG: slider_handle or slider_callback is null

const touch_slider_message_t *touch_slider_get_message(const touch_elem_message_t *element_message)

Touch slider get message.

This function decodes the element message from touch_element_message_receive() and return a slider message pointer.

Parameters

element_message -- [in] element message

Returns

Touch slider message pointer

Structures

struct touch_slider_global_config_t

Slider initialization configuration passed to touch_slider_install.

Public Members

float quantify_lower_threshold

Slider signal quantification threshold.

float threshold_divider

Slider channel threshold divider.

uint16_t filter_reset_time

Slider position filter reset time (Unit is esp_timer callback tick)

uint16_t benchmark_update_time

Slider benchmark update time (Unit is esp_timer callback tick)

uint8_t position_filter_size

Moving window filter buffer size.

uint8_t position_filter_factor

One-order IIR filter factor.

uint8_t calculate_channel_count

The number of channels which will take part in calculation.

struct touch_slider_config_t

Slider configuration (for new instance) passed to touch_slider_create()

Public Members

const touch_pad_t *channel_array

Slider channel array.

const float *sensitivity_array

Slider channel sensitivity array.

uint8_t channel_num

The number of slider channels.

uint8_t position_range

The right region of touch slider position range, [0, position_range (less than or equal to 255)].

struct touch_slider_message_t

Slider message type.

Public Members

touch_slider_event_t event

Slider event.

touch_slider_position_t position

Slider position.

Macros

TOUCH_SLIDER_GLOBAL_DEFAULT_CONFIG()

Type Definitions

typedef uint32_t touch_slider_position_t

Slider position data type.

typedef touch_elem_handle_t touch_slider_handle_t

Slider instance handle.

typedef void (*touch_slider_callback_t)(touch_slider_handle_t, touch_slider_message_t*, void*)

Slider callback type.

Enumerations

enum touch_slider_event_t

Slider event type.

Values:

enumerator TOUCH_SLIDER_EVT_ON_PRESS

Slider on Press event.

enumerator TOUCH_SLIDER_EVT_ON_RELEASE

Slider on Release event.

enumerator TOUCH_SLIDER_EVT_ON_CALCULATION

Slider on Calculation event.

enumerator TOUCH_SLIDER_EVT_MAX

API Reference - Touch Matrix

Header File

  • components/touch_element/include/touch_element/touch_matrix.h

  • This header file can be included with:

    #include "touch_element/touch_matrix.h"

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

    REQUIRES touch_element

    or

    PRIV_REQUIRES touch_element

Functions

esp_err_t touch_matrix_install(const touch_matrix_global_config_t *global_config)

Touch matrix button initialize.

This function initializes touch matrix button object and acts on all touch matrix button instances.

Parameters

global_config -- [in] Touch matrix global initialization configuration

Returns

  • ESP_OK: Successfully initialized touch matrix button

  • ESP_ERR_INVALID_STATE: Touch element library was not initialized

  • ESP_ERR_INVALID_ARG: matrix_init is NULL

  • ESP_ERR_NO_MEM: Insufficient memory

void touch_matrix_uninstall(void)

Release resources allocated using touch_matrix_install()

esp_err_t touch_matrix_create(const touch_matrix_config_t *matrix_config, touch_matrix_handle_t *matrix_handle)

Create a new touch matrix button instance.

Note

Channel array and sensitivity array must be one-one correspondence in those array

Note

Touch matrix button does not support Multi-Touch now

Parameters

  • matrix_config -- [in] Matrix button configuration

  • matrix_handle -- [out] Matrix button handle

Returns

  • ESP_OK: Successfully create touch matrix button

  • ESP_ERR_INVALID_STATE: Touch matrix driver was not initialized

  • ESP_ERR_INVALID_ARG: Invalid configuration struct or arguments is NULL

  • ESP_ERR_NO_MEM: Insufficient memory

esp_err_t touch_matrix_delete(touch_matrix_handle_t matrix_handle)

Release resources allocated using touch_matrix_create()

Parameters

matrix_handle -- [in] Matrix handle

Returns

  • ESP_OK: Successfully released resources

  • ESP_ERR_INVALID_STATE: Touch matrix driver was not initialized

  • ESP_ERR_INVALID_ARG: matrix_handle is null

  • ESP_ERR_NOT_FOUND: Input handle is not a matrix handle

esp_err_t touch_matrix_subscribe_event(touch_matrix_handle_t matrix_handle, uint32_t event_mask, void *arg)

Touch matrix button subscribes event.

This function uses event mask to subscribe to touch matrix events, once one of the subscribed events occurs, the event message could be retrieved by calling touch_element_message_receive() or input callback routine.

Note

Touch matrix button only support three kind of event masks, they are TOUCH_ELEM_EVENT_ON_PRESS, TOUCH_ELEM_EVENT_ON_RELEASE, TOUCH_ELEM_EVENT_ON_LONGPRESS. You can use those event masks in any combination to achieve the desired effect.

Parameters

  • matrix_handle -- [in] Matrix handle

  • event_mask -- [in] Matrix subscription event mask

  • arg -- [in] User input argument

Returns

  • ESP_OK: Successfully subscribed touch matrix event

  • ESP_ERR_INVALID_STATE: Touch matrix driver was not initialized

  • ESP_ERR_INVALID_ARG: matrix_handle is null or event is not supported

esp_err_t touch_matrix_set_dispatch_method(touch_matrix_handle_t matrix_handle, touch_elem_dispatch_t dispatch_method)

Touch matrix button set dispatch method.

This function sets a dispatch method that the driver core will use this method as the event notification method.

Parameters

  • matrix_handle -- [in] Matrix button handle

  • dispatch_method -- [in] Dispatch method (By callback/event)

Returns

  • ESP_OK: Successfully set dispatch method

  • ESP_ERR_INVALID_STATE: Touch matrix driver was not initialized

  • ESP_ERR_INVALID_ARG: matrix_handle is null or dispatch_method is invalid

esp_err_t touch_matrix_set_callback(touch_matrix_handle_t matrix_handle, touch_matrix_callback_t matrix_callback)

Touch matrix button set callback.

This function sets a callback routine into touch element driver core, when the subscribed events occur, the callback routine will be called.

Note

Matrix message will be passed from the callback function and it will be destroyed when the callback function return.

Warning

Since this input callback routine runs on driver core (esp-timer callback routine), it should not do something that attempts to Block, such as calling vTaskDelay().

Parameters

  • matrix_handle -- [in] Matrix button handle

  • matrix_callback -- [in] User input callback

Returns

  • ESP_OK: Successfully set callback

  • ESP_ERR_INVALID_STATE: Touch matrix driver was not initialized

  • ESP_ERR_INVALID_ARG: matrix_handle or matrix_callback is null

esp_err_t touch_matrix_set_longpress(touch_matrix_handle_t matrix_handle, uint32_t threshold_time)

Touch matrix button set long press trigger time.

This function sets the threshold time (ms) for a long press event. If a matrix button is pressed and held for a period of time that exceeds the threshold time, a long press event is triggered.

Parameters

  • matrix_handle -- [in] Matrix button handle

  • threshold_time -- [in] Threshold time (ms) of long press event occur

Returns

  • ESP_OK: Successfully set the time of long press event

  • ESP_ERR_INVALID_STATE: Touch matrix driver was not initialized

  • ESP_ERR_INVALID_ARG: matrix_handle is null or time (ms) is 0

const touch_matrix_message_t *touch_matrix_get_message(const touch_elem_message_t *element_message)

Touch matrix get message.

This function decodes the element message from touch_element_message_receive() and return a matrix message pointer.

Parameters

element_message -- [in] element message

Returns

Touch matrix message pointer

Structures

struct touch_matrix_global_config_t

Matrix button initialization configuration passed to touch_matrix_install.

Public Members

float threshold_divider

Matrix button channel threshold divider.

uint32_t default_lp_time

Matrix button default LongPress event time (ms)

struct touch_matrix_config_t

Matrix button configuration (for new instance) passed to touch_matrix_create()

Public Members

const touch_pad_t *x_channel_array

Matrix button x-axis channels array.

const touch_pad_t *y_channel_array

Matrix button y-axis channels array.

const float *x_sensitivity_array

Matrix button x-axis channels sensitivity array.

const float *y_sensitivity_array

Matrix button y-axis channels sensitivity array.

uint8_t x_channel_num

The number of channels in x-axis.

uint8_t y_channel_num

The number of channels in y-axis.

struct touch_matrix_position_t

Matrix button position data type.

Public Members

uint8_t x_axis

Matrix button x axis position.

uint8_t y_axis

Matrix button y axis position.

uint8_t index

Matrix button position index.

struct touch_matrix_message_t

Matrix message type.

Public Members

touch_matrix_event_t event

Matrix event.

touch_matrix_position_t position

Matrix position.

Macros

TOUCH_MATRIX_GLOBAL_DEFAULT_CONFIG()

Type Definitions

typedef touch_elem_handle_t touch_matrix_handle_t

Matrix button instance handle.

typedef void (*touch_matrix_callback_t)(touch_matrix_handle_t, touch_matrix_message_t*, void*)

Matrix button callback type.

Enumerations

enum touch_matrix_event_t

Matrix button event type.

Values:

enumerator TOUCH_MATRIX_EVT_ON_PRESS

Matrix button Press event.

enumerator TOUCH_MATRIX_EVT_ON_RELEASE

Matrix button Press event.

enumerator TOUCH_MATRIX_EVT_ON_LONGPRESS

Matrix button LongPress event.

enumerator TOUCH_MATRIX_EVT_MAX

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