触摸传感器¶

[English]

概述¶

触摸传感器系统由保护覆盖层、触摸电极、绝缘基板和走线组成，保护覆盖层位于最上层，绝缘基板上设有电极及走线。用户触摸覆盖层将产生电容变化，根据电容变化判断此次触摸是否为有效触摸行为。

ESP32 可支持最多 10 个电容式触摸板/GPIO，触摸板可以以矩阵或滑条等方式组合使用，从而覆盖更大触感区域及更多触感点。触摸传感由有限状态机 (FSM) 硬件控制，由软件或专用硬件计时器发起。

如需了解触摸传感器设计、操作及其控制寄存器等相关信息，请参考《ESP32-S2 技术参考手册》(PDF)，您也可以在《ESP32 技术参考手册》中查看这一子系统是如何运行的。

请参考触摸传感器应用方案简介，查看触摸传感器设计详情和固件开发指南。如果不想亲自在多种配置环境下测试触摸传感器，请查看 ESP32 触摸功能开发套件。

功能介绍¶

下面将 API 分解成几个函数组进行介绍，帮助您快速了解以下功能：

初始化触摸板驱动程序
配置触摸板 GPIO 管脚
触摸状态测量
调整测量参数（优化测量）
过滤触摸测量
触摸监测方式
设置中断信号监测触碰动作
中断触发

请前往 API 参考章节，查看某一函数的具体描述。应用示例章节则介绍了此 API 的具体实现。

初始化触摸板驱动程序¶

使用触摸板之前，需要先调用 touch_pad_init() 函数初始化触摸板驱动程序。此函数设置了 API 参考项下的 Macros 中列出的几项 .._DEFAULT 驱动程序参数，同时删除之前设置过的触摸板信息（如有），并禁用中断。

如果不再需要该驱动程序，可以调用 touch_pad_deinit() 释放已初始化的驱动程序。

配置触摸板 GPIO 管脚¶

调用 touch_pad_config() 使能某一 GPIO 的触感功能。

使用 touch_pad_set_fsm_mode() 选择触摸板测量（由 FSM 操作）是由硬件计时器自动启动，还是由软件自动启动。如果选择软件模式，请使用 touch_pad_sw_start() 启动 FSM。

触摸状态测量¶

借助以下两个函数从传感器读取原始数据或过滤后的数据：

touch_pad_read()
touch_pad_read_filtered()

这两个函数也可以用于检查触碰和释放触摸板时传感器读数变化范围，来评估触摸板设计，然后根据这些信息设定触摸阈值。

注解

使用 touch_pad_read_filtered() 之前，需要先调用过滤触摸测量中特定的滤波器函数初始化并配置该滤波器。

请参考应用示例 peripherals/touch_pad_read，查看如何使用这两个读值函数。

优化测量¶

触摸传感器设有数个可配置参数，以适应触摸板设计特点。例如，如果需要感知较细微的电容变化，则可以缩小触摸板充放电的参考电压范围。您可以使用 touch_pad_set_voltage() 函数设置电压参考低值和参考高值。

优化测量除了可以识别细微的电容变化之外，还可以降低应用程序功耗，但可能会增加测量噪声干扰。如果得到的动态读数范围结果比较理想，则可以调用 touch_pad_set_meas_time() 函数来减少测量时间，从而进一步降低功耗。

可用的测量参数及相应的 ‘set’ 函数总结如下：

触摸板充放电参数：
- 电压门限：touch_pad_set_voltage()
- 速率（斜率） touch_pad_set_cnt_mode()
测量时间：touch_pad_set_meas_time()

电压门限（参考低值/参考高值）、速率（斜率）与测量时间的关系如下图所示：

Touch Pad - relationship between measurement parameters

触摸板 - 测量参数之间的关系¶

上图中的 Output 代表触摸传感器读值，即一个测量周期内测得的脉冲计数值。

所有函数均成对出现，用于设定某一特定参数，并获取当前参数值。例如：touch_pad_set_voltage() 和 touch_pad_get_voltage()。

过滤触摸测量¶

如果测量中存在噪声，可以使用提供的 API 函数对测量进行过滤。使用滤波器之前，请先调用 touch_pad_filter_start() 启动该滤波器。

滤波器类型为 IIR（无限脉冲响应滤波器），您可以调用 touch_pad_set_filter_period() 配置此类滤波器的采样周期。

如需停止滤波器，请调用 touch_pad_filter_stop() 函数。如果不再使用该滤波器，请调用 touch_pad_filter_delete() 删除此滤波器。

触摸监测¶

触摸监测基于用户配置的阈值和 FSM 执行的原始测量，并由 ESP32 硬件实现。你可以调用 touch_pad_get_status() 查看被触碰的触摸板，或调用 touch_pad_clear_status() 清除触摸状态信息。

您也可以将硬件触摸监测连接至中断，详细介绍见下一章节。

如果测量中存在噪声，且电容变化幅度较小，硬件触摸监测结果可能就不太理想。如需解决这一问题，不建议使用硬件监测或中断信号，建议您在自己的应用程序中采用测量过滤，并执行触摸监测。请参考 peripherals/touch_pad_interrupt，查看以上两种触摸监测的实现方式。

中断触发¶

在对触摸监测启用中断之前，请先设置一个触摸监测阈值。然后使用触摸状态测量中所述的函数读取并显示触摸和释放触摸板时测得的结果。如果测量中存在噪声且相对电容变化较小，请使用滤波器。您也可以根据应用程序和环境条件，测试温度和电源电压变化对测量值的影响。

确定监测阈值后就可以在初始化时调用 touch_pad_config() 设置此阈值，或在运行时调用 touch_pad_set_thresh() 设置此阈值。

下一步就是设置如何触发中断。您可以设置在阈值以下或以上触发中断，具体触发模式由函数 touch_pad_set_trigger_mode() 设置。

最后您可以使用以下函数配置和管理中断调用：

touch_pad_isr_register() / touch_pad_isr_deregister()
touch_pad_intr_enable() / touch_pad_intr_disable()

中断配置完成后，您可以调用 touch_pad_get_status() 查看中断信号来自哪个触摸板，也可以调用 touch_pad_clear_status() 清除触摸板状态信息。

注解

触摸监测中的中断信号基于原始/未经过滤的测量值（对比用户设置的阈值），并在硬件中实现。启用软件滤波 API 并不会影响这一过程，见过滤触摸测量。

从睡眠模式唤醒¶

如果使用触摸板中断将芯片从睡眠模式唤醒，您可以选择配置一些触摸板，例如 SET1 或 SET1 和 SET2，触摸这些触摸板将触发中断并唤醒芯片。请调用 touch_pad_set_trigger_source() 实现上述操作。

您可以使用以下函数管理 ‘SET’ 中触摸板所需的位模式配置：

touch_pad_set_group_mask() / touch_pad_get_group_mask()
touch_pad_clear_group_mask()

应用示例¶

触摸传感器读值示例：peripherals/touch_pad_read
触摸传感器中断示例：peripherals/touch_pad_interrupt

API 参考¶

Header File¶

driver/esp32s2/include/driver/touch_sensor.h

Functions¶

esp_err_t touch_pad_fsm_start(void)¶

Set touch sensor FSM start.

Note

Start FSM after the touch sensor FSM mode is set.

Note

Call this function will reset benchmark of all touch channels.

Return

ESP_OK on success

esp_err_t touch_pad_fsm_stop(void)¶

Stop touch sensor FSM.

Return

ESP_OK on success

esp_err_t touch_pad_sw_start(void)¶

Trigger a touch sensor measurement, only support in SW mode of FSM.

Return

ESP_OK on success

esp_err_t touch_pad_set_meas_time(uint16_t sleep_cycle, uint16_t meas_times)¶

Set touch sensor times of charge and discharge and sleep time. Excessive total time will slow down the touch response. Too small measurement time will not be sampled enough, resulting in inaccurate measurements.

Note

The greater the duty cycle of the measurement time, the more system power is consumed.

Return

ESP_OK on success

Parameters

sleep_cycle: The touch sensor will sleep after each measurement. sleep_cycle decide the interval between each measurement. t_sleep = sleep_cycle / (RTC_SLOW_CLK frequency). The approximate frequency value of RTC_SLOW_CLK can be obtained using rtc_clk_slow_freq_get_hz function.
meas_times: The times of charge and discharge in each measure process of touch channels. The timer frequency is 8Mhz. Range: 0 ~ 0xffff. Recommended typical value: Modify this value to make the measurement time around 1ms.

esp_err_t touch_pad_get_meas_time(uint16_t *sleep_cycle, uint16_t *meas_times)¶

Get touch sensor times of charge and discharge and sleep time.

Return

ESP_OK on success

Parameters

sleep_cycle: Pointer to accept sleep cycle number
meas_times: Pointer to accept measurement times count.

esp_err_t touch_pad_set_idle_channel_connect(touch_pad_conn_type_t type)¶

Set connection type of touch channel in idle status. When a channel is in measurement mode, other initialized channels are in idle mode. The touch channel is generally adjacent to the trace, so the connection state of the idle channel affects the stability and sensitivity of the test channel. The CONN_HIGHZ(high resistance) setting increases the sensitivity of touch channels. The CONN_GND(grounding) setting increases the stability of touch channels.

Return

ESP_OK on success

Parameters

type: Select idle channel connect to high resistance state or ground.

esp_err_t touch_pad_get_idle_channel_connect(touch_pad_conn_type_t *type)¶

Set connection type of touch channel in idle status. When a channel is in measurement mode, other initialized channels are in idle mode. The touch channel is generally adjacent to the trace, so the connection state of the idle channel affects the stability and sensitivity of the test channel. The CONN_HIGHZ(high resistance) setting increases the sensitivity of touch channels. The CONN_GND(grounding) setting increases the stability of touch channels.

Return

ESP_OK on success

Parameters

type: Pointer to connection type.

esp_err_t touch_pad_set_thresh(touch_pad_t touch_num, uint32_t threshold)¶

Set the trigger threshold of touch sensor. The threshold determines the sensitivity of the touch sensor. The threshold is the original value of the trigger state minus the benchmark value.

Note

If set “TOUCH_PAD_THRESHOLD_MAX”, the touch is never be triggered.

Return

ESP_OK on success

Parameters

touch_num: touch pad index
threshold: threshold of touch sensor. Should be less than the max change value of touch.

esp_err_t touch_pad_get_thresh(touch_pad_t touch_num, uint32_t *threshold)¶

Get touch sensor trigger threshold.

Return

ESP_OK on success
ESP_ERR_INVALID_ARG if argument is wrong

Parameters

touch_num: touch pad index
threshold: pointer to accept threshold

esp_err_t touch_pad_set_channel_mask(uint16_t enable_mask)¶

Register touch channel into touch sensor scan group. The working mode of the touch sensor is cyclically scanned. This function will set the scan bits according to the given bitmask.

Note

If set this mask, the FSM timer should be stop firsty.

Note

The touch sensor that in scan map, should be deinit GPIO function firstly by touch_pad_io_init.

Return

ESP_OK on success

Parameters

enable_mask: bitmask of touch sensor scan group. e.g. TOUCH_PAD_NUM14 -> BIT(14)

esp_err_t touch_pad_get_channel_mask(uint16_t *enable_mask)¶

Get the touch sensor scan group bit mask.

Return

ESP_OK on success

Parameters

enable_mask: Pointer to bitmask of touch sensor scan group. e.g. TOUCH_PAD_NUM14 -> BIT(14)

esp_err_t touch_pad_clear_channel_mask(uint16_t enable_mask)¶

Clear touch channel from touch sensor scan group. The working mode of the touch sensor is cyclically scanned. This function will clear the scan bits according to the given bitmask.

Note

If clear all mask, the FSM timer should be stop firsty.

Return

ESP_OK on success

Parameters

enable_mask: bitmask of touch sensor scan group. e.g. TOUCH_PAD_NUM14 -> BIT(14)

esp_err_t touch_pad_config(touch_pad_t touch_num)¶

Configure parameter for each touch channel.

Note

Touch num 0 is denoise channel, please use touch_pad_denoise_enable to set denoise function

Return

ESP_OK Success
ESP_ERR_INVALID_ARG if argument wrong
ESP_FAIL if touch pad not initialized

Parameters

touch_num: touch pad index

esp_err_t touch_pad_reset(void)¶

Reset the FSM of touch module.

Note

Call this function after touch_pad_fsm_stop.

Return

ESP_OK Success

touch_pad_t touch_pad_get_current_meas_channel(void)¶

Get the current measure channel.

Note

Should be called when touch sensor measurement is in cyclic scan mode.

Return

touch channel number

uint32_t touch_pad_read_intr_status_mask(void)¶

Get the touch sensor interrupt status mask.

Return

touch interrupt bit

esp_err_t touch_pad_intr_enable(touch_pad_intr_mask_t int_mask)¶

Enable touch sensor interrupt by bitmask.

Note

This API can be called in ISR handler.

Return

ESP_OK on success

Parameters

int_mask: Pad mask to enable interrupts

esp_err_t touch_pad_intr_disable(touch_pad_intr_mask_t int_mask)¶

Disable touch sensor interrupt by bitmask.

Note

This API can be called in ISR handler.

Return

ESP_OK on success

Parameters

int_mask: Pad mask to disable interrupts

esp_err_t touch_pad_intr_clear(touch_pad_intr_mask_t int_mask)¶

Clear touch sensor interrupt by bitmask.

Return

ESP_OK on success

Parameters

int_mask: Pad mask to clear interrupts

esp_err_t touch_pad_isr_register(intr_handler_t fn, void *arg, touch_pad_intr_mask_t intr_mask)¶

Register touch-pad ISR. The handler will be attached to the same CPU core that this function is running on.

Return

ESP_OK Success
ESP_ERR_INVALID_ARG Arguments error
ESP_ERR_NO_MEM No memory

Parameters

fn: Pointer to ISR handler
arg: Parameter for ISR
intr_mask: Enable touch sensor interrupt handler by bitmask.

esp_err_t touch_pad_timeout_set(bool enable, uint32_t threshold)¶

Enable/disable the timeout check and set timeout threshold for all touch sensor channels measurements. If enable: When the touch reading of a touch channel exceeds the measurement threshold, a timeout interrupt will be generated. If disable: the FSM does not check if the channel under measurement times out.

Note

The threshold compared with touch readings.

Note

In order to avoid abnormal short circuit of some touch channels. This function should be turned on. Ensure the normal operation of other touch channels.

Return

ESP_OK Success

Parameters

enable: true(default): Enable the timeout check; false: Disable the timeout check.
threshold: For all channels, the maximum value that will not be exceeded during normal operation.

esp_err_t touch_pad_timeout_resume(void)¶

Call this interface after timeout to make the touch channel resume normal work. Point on the next channel to measure. If this API is not called, the touch FSM will stop the measurement after timeout interrupt.

Note

Call this API after finishes the exception handling by user.

Return

ESP_OK Success

esp_err_t touch_pad_read_raw_data(touch_pad_t touch_num, uint32_t *raw_data)¶

get raw data of touch sensor.

Note

After the initialization is complete, the “raw_data” is max value. You need to wait for a measurement cycle before you can read the correct touch value.

Return

ESP_OK Success
ESP_FAIL Touch channel 0 haven’t this parameter.

Parameters

touch_num: touch pad index
raw_data: pointer to accept touch sensor value

esp_err_t touch_pad_read_benchmark(touch_pad_t touch_num, uint32_t *benchmark)¶

get benchmark of touch sensor.

Note

After initialization, the benchmark value is the maximum during the first measurement period.

Return

ESP_OK Success
ESP_ERR_INVALID_ARG Touch channel 0 haven’t this parameter.

Parameters

touch_num: touch pad index
benchmark: pointer to accept touch sensor benchmark value

esp_err_t touch_pad_filter_read_smooth(touch_pad_t touch_num, uint32_t *smooth)¶

Get smoothed data that obtained by filtering the raw data.

Parameters

touch_num: touch pad index
smooth: pointer to smoothed data

esp_err_t touch_pad_reset_benchmark(touch_pad_t touch_num)¶

Force reset benchmark to raw data of touch sensor.

Return

ESP_OK Success

Parameters

touch_num: touch pad index
- TOUCH_PAD_MAX Reset basaline of all channels

esp_err_t touch_pad_filter_set_config(touch_filter_config_t *filter_info)¶

set parameter of touch sensor filter and detection algorithm. For more details on the detection algorithm, please refer to the application documentation.

Return

ESP_OK Success

Parameters

filter_info: select filter type and threshold of detection algorithm

esp_err_t touch_pad_filter_get_config(touch_filter_config_t *filter_info)¶

get parameter of touch sensor filter and detection algorithm. For more details on the detection algorithm, please refer to the application documentation.

Return

ESP_OK Success

Parameters

filter_info: select filter type and threshold of detection algorithm

esp_err_t touch_pad_filter_enable(void)¶

enable touch sensor filter for detection algorithm. For more details on the detection algorithm, please refer to the application documentation.

Return

ESP_OK Success

esp_err_t touch_pad_filter_disable(void)¶

disable touch sensor filter for detection algorithm. For more details on the detection algorithm, please refer to the application documentation.

Return

ESP_OK Success

esp_err_t touch_pad_denoise_set_config(touch_pad_denoise_t *denoise)¶

set parameter of denoise pad (TOUCH_PAD_NUM0). T0 is an internal channel that does not have a corresponding external GPIO. T0 will work simultaneously with the measured channel Tn. Finally, the actual measured value of Tn is the value after subtracting lower bits of T0. The noise reduction function filters out interference introduced simultaneously on all channels, such as noise introduced by power supplies and external EMI.

Return

ESP_OK Success

Parameters

denoise: parameter of denoise

esp_err_t touch_pad_denoise_get_config(touch_pad_denoise_t *denoise)¶

get parameter of denoise pad (TOUCH_PAD_NUM0).

Return

ESP_OK Success

Parameters

denoise: Pointer to parameter of denoise

esp_err_t touch_pad_denoise_enable(void)¶

enable denoise function. T0 is an internal channel that does not have a corresponding external GPIO. T0 will work simultaneously with the measured channel Tn. Finally, the actual measured value of Tn is the value after subtracting lower bits of T0. The noise reduction function filters out interference introduced simultaneously on all channels, such as noise introduced by power supplies and external EMI.

Return

ESP_OK Success

esp_err_t touch_pad_denoise_disable(void)¶

disable denoise function.

Return

ESP_OK Success

esp_err_t touch_pad_denoise_read_data(uint32_t *data)¶

Get denoise measure value (TOUCH_PAD_NUM0).

Return

ESP_OK Success

Parameters

data: Pointer to receive denoise value

esp_err_t touch_pad_waterproof_set_config(touch_pad_waterproof_t *waterproof)¶

set parameter of waterproof function.

   The waterproof function includes a shielded channel (TOUCH_PAD_NUM14) and a guard channel.
   Guard pad is used to detect the large area of water covering the touch panel.
   Shield pad is used to shield the influence of water droplets covering the touch panel.
   It is generally designed as a grid and is placed around the touch buttons.

Return

ESP_OK Success

Parameters

waterproof: parameter of waterproof

esp_err_t touch_pad_waterproof_get_config(touch_pad_waterproof_t *waterproof)¶

get parameter of waterproof function.

Return

ESP_OK Success

Parameters

waterproof: parameter of waterproof

esp_err_t touch_pad_waterproof_enable(void)¶

Enable parameter of waterproof function. Should be called after function touch_pad_waterproof_set_config.

Return

ESP_OK Success

esp_err_t touch_pad_waterproof_disable(void)¶

Disable parameter of waterproof function.

Return

ESP_OK Success

esp_err_t touch_pad_proximity_enable(touch_pad_t touch_num, bool enabled)¶

Enable/disable proximity function of touch channels. The proximity sensor measurement is the accumulation of touch channel measurements.

Note

Supports up to three touch channels configured as proximity sensors.

Return

ESP_OK: Configured correctly.
ESP_ERR_INVALID_ARG: Touch channel number error.
ESP_ERR_NOT_SUPPORTED: Don’t support configured.

Parameters

touch_num: touch pad index
enabled: true: enable the proximity function; false: disable the proximity function

esp_err_t touch_pad_proximity_set_count(touch_pad_t touch_num, uint32_t count)¶

Set measure count of proximity channel. The proximity sensor measurement is the accumulation of touch channel measurements.

Note

All proximity channels use the same count value. So please pass the parameter TOUCH_PAD_MAX.

Return

ESP_OK: Configured correctly.
ESP_ERR_INVALID_ARG: Touch channel number error.

Parameters

touch_num: Touch pad index. In this version, pass the parameter TOUCH_PAD_MAX.
count: The cumulative times of measurements for proximity pad. Range: 0 ~ 255.

esp_err_t touch_pad_proximity_get_count(touch_pad_t touch_num, uint32_t *count)¶

Get measure count of proximity channel. The proximity sensor measurement is the accumulation of touch channel measurements.

Note

All proximity channels use the same count value. So please pass the parameter TOUCH_PAD_MAX.

Return

ESP_OK: Configured correctly.
ESP_ERR_INVALID_ARG: Touch channel number error.

Parameters

touch_num: Touch pad index. In this version, pass the parameter TOUCH_PAD_MAX.
count: The cumulative times of measurements for proximity pad. Range: 0 ~ 255.

esp_err_t touch_pad_proximity_get_data(touch_pad_t touch_num, uint32_t *measure_out)¶

Get the accumulated measurement of the proximity sensor. The proximity sensor measurement is the accumulation of touch channel measurements.

Return

ESP_OK Success
ESP_ERR_INVALID_ARG Touch num is not proximity

Parameters

touch_num: touch pad index
measure_out: If the accumulation process does not end, the measure_out is the process value.

esp_err_t touch_pad_sleep_channel_get_info(touch_pad_sleep_channel_t *slp_config)¶

Get parameter of touch sensor sleep channel. The touch sensor can works in sleep mode to wake up sleep.

Note

After the sleep channel is configured, Please use special functions for sleep channel. e.g. The user should uses touch_pad_sleep_channel_read_data instead of touch_pad_read_raw_data to obtain the sleep channel reading.

Return

ESP_OK Success

Parameters

slp_config: touch sleep pad config.

esp_err_t touch_pad_sleep_channel_enable(touch_pad_t pad_num, bool enable)¶

Enable/Disable sleep channel function for touch sensor. The touch sensor can works in sleep mode to wake up sleep.

Note

ESP32S2 only support one sleep channel.

Note

After the sleep channel is configured, Please use special functions for sleep channel. e.g. The user should uses touch_pad_sleep_channel_read_data instead of touch_pad_read_raw_data to obtain the sleep channel reading.

Return

ESP_OK Success

Parameters

pad_num: Set touch channel number for sleep pad. Only one touch sensor channel is supported in deep sleep mode.
enable: true: enable sleep pad for touch sensor; false: disable sleep pad for touch sensor;

esp_err_t touch_pad_sleep_channel_enable_proximity(touch_pad_t pad_num, bool enable)¶

Enable/Disable proximity function for sleep channel. The touch sensor can works in sleep mode to wake up sleep.

Note

ESP32S2 only support one sleep channel.

Return

ESP_OK Success

Parameters

pad_num: Set touch channel number for sleep pad. Only one touch sensor channel is supported in deep sleep mode.
enable: true: enable proximity for sleep channel; false: disable proximity for sleep channel;

esp_err_t touch_pad_sleep_set_threshold(touch_pad_t pad_num, uint32_t touch_thres)¶

Set the trigger threshold of touch sensor in deep sleep. The threshold determines the sensitivity of the touch sensor.

Note

In general, the touch threshold during sleep can use the threshold parameter parameters before sleep.

Return

ESP_OK Success

Parameters

pad_num: Set touch channel number for sleep pad. Only one touch sensor channel is supported in deep sleep mode.
touch_thres: touch sleep pad threshold

esp_err_t touch_pad_sleep_get_threshold(touch_pad_t pad_num, uint32_t *touch_thres)¶

Get the trigger threshold of touch sensor in deep sleep. The threshold determines the sensitivity of the touch sensor.

Note

In general, the touch threshold during sleep can use the threshold parameter parameters before sleep.

Return

ESP_OK Success

Parameters

pad_num: Set touch channel number for sleep pad. Only one touch sensor channel is supported in deep sleep mode.
touch_thres: touch sleep pad threshold

esp_err_t touch_pad_sleep_channel_read_benchmark(touch_pad_t pad_num, uint32_t *benchmark)¶

Read benchmark of touch sensor sleep channel.

Return

ESP_OK Success
ESP_ERR_INVALID_ARG parameter is NULL

Parameters

pad_num: Set touch channel number for sleep pad. Only one touch sensor channel is supported in deep sleep mode.
benchmark: pointer to accept touch sensor benchmark value

esp_err_t touch_pad_sleep_channel_read_smooth(touch_pad_t pad_num, uint32_t *smooth_data)¶

Read smoothed data of touch sensor sleep channel. Smoothed data is filtered from the raw data.

Return

ESP_OK Success
ESP_ERR_INVALID_ARG parameter is NULL

Parameters

pad_num: Set touch channel number for sleep pad. Only one touch sensor channel is supported in deep sleep mode.
smooth_data: pointer to accept touch sensor smoothed data

esp_err_t touch_pad_sleep_channel_read_data(touch_pad_t pad_num, uint32_t *raw_data)¶

Read raw data of touch sensor sleep channel.

Return

ESP_OK Success
ESP_ERR_INVALID_ARG parameter is NULL

Parameters

pad_num: Set touch channel number for sleep pad. Only one touch sensor channel is supported in deep sleep mode.
raw_data: pointer to accept touch sensor raw data

esp_err_t touch_pad_sleep_channel_reset_benchmark(void)¶

Reset benchmark of touch sensor sleep channel.

Return

ESP_OK Success

esp_err_t touch_pad_sleep_channel_read_proximity_cnt(touch_pad_t pad_num, uint32_t *proximity_cnt)¶

Read proximity count of touch sensor sleep channel.

Return

ESP_OK Success
ESP_ERR_INVALID_ARG parameter is NULL

Parameters

pad_num: Set touch channel number for sleep pad. Only one touch sensor channel is supported in deep sleep mode.
proximity_cnt: pointer to accept touch sensor proximity count value

esp_err_t touch_pad_sleep_channel_set_work_time(uint16_t sleep_cycle, uint16_t meas_times)¶

Change the operating frequency of touch pad in deep sleep state. Reducing the operating frequency can effectively reduce power consumption. If this function is not called, the working frequency of touch in the deep sleep state is the same as that in the wake-up state.

Return

ESP_OK Success

Parameters

sleep_cycle: The touch sensor will sleep after each measurement. sleep_cycle decide the interval between each measurement. t_sleep = sleep_cycle / (RTC_SLOW_CLK frequency). The approximate frequency value of RTC_SLOW_CLK can be obtained using rtc_clk_slow_freq_get_hz function.
meas_times: The times of charge and discharge in each measure process of touch channels. The timer frequency is 8Mhz. Range: 0 ~ 0xffff. Recommended typical value: Modify this value to make the measurement time around 1ms.

Header File¶

driver/include/driver/touch_sensor_common.h

Functions¶

esp_err_t touch_pad_init(void)¶

Initialize touch module.

Note

If default parameter don’t match the usage scenario, it can be changed after this function.

Return

ESP_OK Success
ESP_ERR_NO_MEM Touch pad init error
ESP_ERR_NOT_SUPPORTED Touch pad is providing current to external XTAL

esp_err_t touch_pad_deinit(void)¶

Un-install touch pad driver.

Note

After this function is called, other touch functions are prohibited from being called.

Return

ESP_OK Success
ESP_FAIL Touch pad driver not initialized

esp_err_t touch_pad_io_init(touch_pad_t touch_num)¶

Initialize touch pad GPIO.

Return

ESP_OK on success
ESP_ERR_INVALID_ARG if argument is wrong

Parameters

touch_num: touch pad index

esp_err_t touch_pad_set_voltage(touch_high_volt_t refh, touch_low_volt_t refl, touch_volt_atten_t atten)¶

Set touch sensor high voltage threshold of chanrge. The touch sensor measures the channel capacitance value by charging and discharging the channel. So the high threshold should be less than the supply voltage.

Return

ESP_OK on success
ESP_ERR_INVALID_ARG if argument is wrong

Parameters

refh: the value of DREFH
refl: the value of DREFL
atten: the attenuation on DREFH

esp_err_t touch_pad_get_voltage(touch_high_volt_t *refh, touch_low_volt_t *refl, touch_volt_atten_t *atten)¶

Get touch sensor reference voltage,.

Return

ESP_OK on success

Parameters

refh: pointer to accept DREFH value
refl: pointer to accept DREFL value
atten: pointer to accept the attenuation on DREFH

esp_err_t touch_pad_set_cnt_mode(touch_pad_t touch_num, touch_cnt_slope_t slope, touch_tie_opt_t opt)¶

Set touch sensor charge/discharge speed for each pad. If the slope is 0, the counter would always be zero. If the slope is 1, the charging and discharging would be slow, accordingly. If the slope is set 7, which is the maximum value, the charging and discharging would be fast.

Note

The higher the charge and discharge current, the greater the immunity of the touch channel, but it will increase the system power consumption.

Return

ESP_OK on success
ESP_ERR_INVALID_ARG if argument is wrong

Parameters

touch_num: touch pad index
slope: touch pad charge/discharge speed
opt: the initial voltage

esp_err_t touch_pad_get_cnt_mode(touch_pad_t touch_num, touch_cnt_slope_t *slope, touch_tie_opt_t *opt)¶

Get touch sensor charge/discharge speed for each pad.

Return

ESP_OK on success
ESP_ERR_INVALID_ARG if argument is wrong

Parameters

touch_num: touch pad index
slope: pointer to accept touch pad charge/discharge slope
opt: pointer to accept the initial voltage

esp_err_t touch_pad_isr_deregister(void (*fn)(void *), void *arg, )¶

Deregister the handler previously registered using touch_pad_isr_handler_register.

Return

ESP_OK on success
ESP_ERR_INVALID_STATE if a handler matching both fn and arg isn’t registered

Parameters

fn: handler function to call (as passed to touch_pad_isr_handler_register)
arg: argument of the handler (as passed to touch_pad_isr_handler_register)

esp_err_t touch_pad_get_wakeup_status(touch_pad_t *pad_num)¶

Get the touch pad which caused wakeup from deep sleep.

Return

ESP_OK Success
ESP_ERR_INVALID_ARG parameter is NULL

Parameters

pad_num: pointer to touch pad which caused wakeup

esp_err_t touch_pad_set_fsm_mode(touch_fsm_mode_t mode)¶

Set touch sensor FSM mode, the test action can be triggered by the timer, as well as by the software.

Return

ESP_OK on success
ESP_ERR_INVALID_ARG if argument is wrong

Parameters

mode: FSM mode

esp_err_t touch_pad_get_fsm_mode(touch_fsm_mode_t *mode)¶

Get touch sensor FSM mode.

Return

ESP_OK on success

Parameters

mode: pointer to accept FSM mode

esp_err_t touch_pad_clear_status(void)¶

To clear the touch sensor channel active status.

Note

The FSM automatically updates the touch sensor status. It is generally not necessary to call this API to clear the status.

Return

ESP_OK on success

uint32_t touch_pad_get_status(void)¶

Get the touch sensor channel active status mask. The bit position represents the channel number. The 0/1 status of the bit represents the trigger status.

Return

The touch sensor status. e.g. Touch1 trigger status is status_mask & (BIT1).

bool touch_pad_meas_is_done(void)¶

Check touch sensor measurement status.

Return

True measurement is under way
False measurement done

GPIO 宏查找表¶

您可以使用宏定义某一触摸板通道的 GPIO，或定义某一 GPIO 的通道。例如：

TOUCH_PAD_NUM5_GPIO_NUM 定义了通道 5 的 GPIO（即 GPIO 12）；
TOUCH_PAD_GPIO4_CHANNEL 定义了 GPIO 4 的通道（即通道 0）。

Header File¶

soc/esp32s2/include/soc/touch_sensor_channel.h

Macros¶

TOUCH_PAD_GPIO1_CHANNEL¶

TOUCH_PAD_NUM1_GPIO_NUM¶

TOUCH_PAD_GPIO2_CHANNEL¶

TOUCH_PAD_NUM2_GPIO_NUM¶

TOUCH_PAD_GPIO3_CHANNEL¶

TOUCH_PAD_NUM3_GPIO_NUM¶

TOUCH_PAD_GPIO4_CHANNEL¶

TOUCH_PAD_NUM4_GPIO_NUM¶

TOUCH_PAD_GPIO5_CHANNEL¶

TOUCH_PAD_NUM5_GPIO_NUM¶

TOUCH_PAD_GPIO6_CHANNEL¶

TOUCH_PAD_NUM6_GPIO_NUM¶

TOUCH_PAD_GPIO7_CHANNEL¶

TOUCH_PAD_NUM7_GPIO_NUM¶

TOUCH_PAD_GPIO8_CHANNEL¶

TOUCH_PAD_NUM8_GPIO_NUM¶

TOUCH_PAD_GPIO9_CHANNEL¶

TOUCH_PAD_NUM9_GPIO_NUM¶

TOUCH_PAD_GPIO10_CHANNEL¶

TOUCH_PAD_NUM10_GPIO_NUM¶

TOUCH_PAD_GPIO11_CHANNEL¶

TOUCH_PAD_NUM11_GPIO_NUM¶

TOUCH_PAD_GPIO12_CHANNEL¶

TOUCH_PAD_NUM12_GPIO_NUM¶

TOUCH_PAD_GPIO13_CHANNEL¶

TOUCH_PAD_NUM13_GPIO_NUM¶

TOUCH_PAD_GPIO14_CHANNEL¶

TOUCH_PAD_NUM14_GPIO_NUM¶

Header File¶

hal/include/hal/touch_sensor_types.h

Structures¶

struct touch_pad_denoise¶

Touch sensor denoise configuration

Public Members

touch_pad_denoise_grade_t grade¶: Select denoise range of denoise channel. Determined by measuring the noise amplitude of the denoise channel.

touch_pad_denoise_cap_t cap_level¶: Select internal reference capacitance of denoise channel. Ensure that the denoise readings are closest to the readings of the channel being measured. Use touch_pad_denoise_read_data to get the reading of denoise channel. The equivalent capacitance of the shielded channel can be calculated from the reading of denoise channel.

struct touch_pad_waterproof¶

Touch sensor waterproof configuration

Public Members

touch_pad_t guard_ring_pad¶: Waterproof. Select touch channel use for guard pad. Guard pad is used to detect the large area of water covering the touch panel.

touch_pad_shield_driver_t shield_driver¶: Waterproof. Shield channel drive capability configuration. Shield pad is used to shield the influence of water droplets covering the touch panel. When the waterproof function is enabled, Touch14 is set as shield channel by default. The larger the parasitic capacitance on the shielding channel, the higher the drive capability needs to be set. The equivalent capacitance of the shield channel can be estimated through the reading value of the denoise channel(Touch0).

struct touch_filter_config¶

Touch sensor filter configuration

Public Members

touch_filter_mode_t mode¶: Set filter mode. The input of the filter is the raw value of touch reading, and the output of the filter is involved in the judgment of the touch state.

uint32_t debounce_cnt¶: Set debounce count, such as n. If the measured values continue to exceed the threshold for n+1 times, the touch sensor state changes. Range: 0 ~ 7

uint32_t noise_thr¶: Noise threshold coefficient. Higher = More noise resistance. The actual noise should be less than (noise coefficient * touch threshold). Range: 0 ~ 3. The coefficient is 0: 4/8; 1: 3/8; 2: 2/8; 3: 1;

uint32_t jitter_step¶: Set jitter filter step size. Range: 0 ~ 15

touch_smooth_mode_t smh_lvl¶: Level of filter applied on the original data against large noise interference.

struct touch_pad_sleep_channel_t¶

Touch sensor channel sleep configuration

Public Members

touch_pad_t touch_num¶: Set touch channel number for sleep pad. Only one touch sensor channel is supported in deep sleep mode. If clear the sleep channel, point this pad to TOUCH_PAD_NUM0

bool en_proximity¶: enable proximity function for sleep pad

Macros¶

TOUCH_PAD_BIT_MASK_ALL¶

TOUCH_PAD_SLOPE_DEFAULT¶

TOUCH_PAD_TIE_OPT_DEFAULT¶

TOUCH_PAD_BIT_MASK_MAX¶

TOUCH_PAD_HIGH_VOLTAGE_THRESHOLD¶

TOUCH_PAD_LOW_VOLTAGE_THRESHOLD¶

TOUCH_PAD_ATTEN_VOLTAGE_THRESHOLD¶

TOUCH_PAD_IDLE_CH_CONNECT_DEFAULT¶

TOUCH_PAD_THRESHOLD_MAX¶: If set touch threshold max value, The touch sensor can’t be in touched status

TOUCH_PAD_SLEEP_CYCLE_DEFAULT¶

Excessive total time will slow down the touch response. Too small measurement time will not be sampled enough, resulting in inaccurate measurements.

Note: The greater the duty cycle of the measurement time, the more system power is consumed. The number of sleep cycle in each measure process of touch channels. The timer frequency is RTC_SLOW_CLK (can be 150k or 32k depending on the options). Range: 0 ~ 0xffff

TOUCH_PAD_MEASURE_CYCLE_DEFAULT¶: The times of charge and discharge in each measure process of touch channels. The timer frequency is 8Mhz. Recommended typical value: Modify this value to make the measurement time around 1ms. Range: 0 ~ 0xffff

TOUCH_PAD_INTR_MASK_ALL¶: All touch interrupt type enable.

TOUCH_PROXIMITY_MEAS_NUM_MAX¶: Touch sensor proximity detection configuration

TOUCH_DEBOUNCE_CNT_MAX¶

TOUCH_NOISE_THR_MAX¶

TOUCH_JITTER_STEP_MAX¶

Type Definitions¶

typedef struct touch_pad_denoise touch_pad_denoise_t¶: Touch sensor denoise configuration

typedef struct touch_pad_waterproof touch_pad_waterproof_t¶: Touch sensor waterproof configuration

typedef struct touch_filter_config touch_filter_config_t¶: Touch sensor filter configuration

Enumerations¶

enum touch_pad_t¶

Touch pad channel

Values:

TOUCH_PAD_NUM0 = 0¶: Touch pad channel 0 is GPIO4(ESP32)

TOUCH_PAD_NUM1¶: Touch pad channel 1 is GPIO0(ESP32) / GPIO1(ESP32-S2)

TOUCH_PAD_NUM2¶: Touch pad channel 2 is GPIO2(ESP32) / GPIO2(ESP32-S2)

TOUCH_PAD_NUM3¶: Touch pad channel 3 is GPIO15(ESP32) / GPIO3(ESP32-S2)

TOUCH_PAD_NUM4¶: Touch pad channel 4 is GPIO13(ESP32) / GPIO4(ESP32-S2)

TOUCH_PAD_NUM5¶: Touch pad channel 5 is GPIO12(ESP32) / GPIO5(ESP32-S2)

TOUCH_PAD_NUM6¶: Touch pad channel 6 is GPIO14(ESP32) / GPIO6(ESP32-S2)

TOUCH_PAD_NUM7¶: Touch pad channel 7 is GPIO27(ESP32) / GPIO7(ESP32-S2)

TOUCH_PAD_NUM8¶: Touch pad channel 8 is GPIO33(ESP32) / GPIO8(ESP32-S2)

TOUCH_PAD_NUM9¶: Touch pad channel 9 is GPIO32(ESP32) / GPIO9(ESP32-S2)

TOUCH_PAD_NUM10¶: Touch channel 10 is GPIO10(ESP32-S2)

TOUCH_PAD_NUM11¶: Touch channel 11 is GPIO11(ESP32-S2)

TOUCH_PAD_NUM12¶: Touch channel 12 is GPIO12(ESP32-S2)

TOUCH_PAD_NUM13¶: Touch channel 13 is GPIO13(ESP32-S2)

TOUCH_PAD_NUM14¶: Touch channel 14 is GPIO14(ESP32-S2)

TOUCH_PAD_MAX¶

enum touch_high_volt_t¶

Touch sensor high reference voltage

Values:

TOUCH_HVOLT_KEEP = -1¶: Touch sensor high reference voltage, no change

TOUCH_HVOLT_2V4 = 0¶: Touch sensor high reference voltage, 2.4V

TOUCH_HVOLT_2V5¶: Touch sensor high reference voltage, 2.5V

TOUCH_HVOLT_2V6¶: Touch sensor high reference voltage, 2.6V

TOUCH_HVOLT_2V7¶: Touch sensor high reference voltage, 2.7V

TOUCH_HVOLT_MAX¶

enum touch_low_volt_t¶

Touch sensor low reference voltage

Values:

TOUCH_LVOLT_KEEP = -1¶: Touch sensor low reference voltage, no change

TOUCH_LVOLT_0V5 = 0¶: Touch sensor low reference voltage, 0.5V

TOUCH_LVOLT_0V6¶: Touch sensor low reference voltage, 0.6V

TOUCH_LVOLT_0V7¶: Touch sensor low reference voltage, 0.7V

TOUCH_LVOLT_0V8¶: Touch sensor low reference voltage, 0.8V

TOUCH_LVOLT_MAX¶

enum touch_volt_atten_t¶

Touch sensor high reference voltage attenuation

Values:

TOUCH_HVOLT_ATTEN_KEEP = -1¶: Touch sensor high reference voltage attenuation, no change

TOUCH_HVOLT_ATTEN_1V5 = 0¶: Touch sensor high reference voltage attenuation, 1.5V attenuation

TOUCH_HVOLT_ATTEN_1V¶: Touch sensor high reference voltage attenuation, 1.0V attenuation

TOUCH_HVOLT_ATTEN_0V5¶: Touch sensor high reference voltage attenuation, 0.5V attenuation

TOUCH_HVOLT_ATTEN_0V¶: Touch sensor high reference voltage attenuation, 0V attenuation

TOUCH_HVOLT_ATTEN_MAX¶

enum touch_cnt_slope_t¶

Touch sensor charge/discharge speed

Values:

TOUCH_PAD_SLOPE_0 = 0¶: Touch sensor charge / discharge speed, always zero

TOUCH_PAD_SLOPE_1 = 1¶: Touch sensor charge / discharge speed, slowest

TOUCH_PAD_SLOPE_2 = 2¶: Touch sensor charge / discharge speed

TOUCH_PAD_SLOPE_3 = 3¶: Touch sensor charge / discharge speed

TOUCH_PAD_SLOPE_4 = 4¶: Touch sensor charge / discharge speed

TOUCH_PAD_SLOPE_5 = 5¶: Touch sensor charge / discharge speed

TOUCH_PAD_SLOPE_6 = 6¶: Touch sensor charge / discharge speed

TOUCH_PAD_SLOPE_7 = 7¶: Touch sensor charge / discharge speed, fast

TOUCH_PAD_SLOPE_MAX¶

enum touch_tie_opt_t¶

Touch sensor initial charge level

Values:

TOUCH_PAD_TIE_OPT_LOW = 0¶: Initial level of charging voltage, low level

TOUCH_PAD_TIE_OPT_HIGH = 1¶: Initial level of charging voltage, high level

TOUCH_PAD_TIE_OPT_MAX¶

enum touch_fsm_mode_t¶

Touch sensor FSM mode

Values:

TOUCH_FSM_MODE_TIMER = 0¶: To start touch FSM by timer

TOUCH_FSM_MODE_SW¶: To start touch FSM by software trigger

TOUCH_FSM_MODE_MAX¶

enum touch_trigger_mode_t¶

Values:

TOUCH_TRIGGER_BELOW = 0¶: Touch interrupt will happen if counter value is less than threshold.

TOUCH_TRIGGER_ABOVE = 1¶: Touch interrupt will happen if counter value is larger than threshold.

TOUCH_TRIGGER_MAX¶

enum touch_trigger_src_t¶

Values:

TOUCH_TRIGGER_SOURCE_BOTH = 0¶: wakeup interrupt is generated if both SET1 and SET2 are “touched”

TOUCH_TRIGGER_SOURCE_SET1 = 1¶: wakeup interrupt is generated if SET1 is “touched”

TOUCH_TRIGGER_SOURCE_MAX¶

enum touch_pad_intr_mask_t¶

Values:

TOUCH_PAD_INTR_MASK_DONE = BIT(0)¶: Measurement done for one of the enabled channels.

TOUCH_PAD_INTR_MASK_ACTIVE = BIT(1)¶: Active for one of the enabled channels.

TOUCH_PAD_INTR_MASK_INACTIVE = BIT(2)¶: Inactive for one of the enabled channels.

TOUCH_PAD_INTR_MASK_SCAN_DONE = BIT(3)¶: Measurement done for all the enabled channels.

TOUCH_PAD_INTR_MASK_TIMEOUT = BIT(4)¶: Timeout for one of the enabled channels.

enum touch_pad_denoise_grade_t¶

Values:

TOUCH_PAD_DENOISE_BIT12 = 0¶: Denoise range is 12bit

TOUCH_PAD_DENOISE_BIT10 = 1¶: Denoise range is 10bit

TOUCH_PAD_DENOISE_BIT8 = 2¶: Denoise range is 8bit

TOUCH_PAD_DENOISE_BIT4 = 3¶: Denoise range is 4bit

TOUCH_PAD_DENOISE_MAX¶

enum touch_pad_denoise_cap_t¶

Values:

TOUCH_PAD_DENOISE_CAP_L0 = 0¶: Denoise channel internal reference capacitance is 5pf

TOUCH_PAD_DENOISE_CAP_L1 = 1¶: Denoise channel internal reference capacitance is 6.4pf

TOUCH_PAD_DENOISE_CAP_L2 = 2¶: Denoise channel internal reference capacitance is 7.8pf

TOUCH_PAD_DENOISE_CAP_L3 = 3¶: Denoise channel internal reference capacitance is 9.2pf

TOUCH_PAD_DENOISE_CAP_L4 = 4¶: Denoise channel internal reference capacitance is 10.6pf

TOUCH_PAD_DENOISE_CAP_L5 = 5¶: Denoise channel internal reference capacitance is 12.0pf

TOUCH_PAD_DENOISE_CAP_L6 = 6¶: Denoise channel internal reference capacitance is 13.4pf

TOUCH_PAD_DENOISE_CAP_L7 = 7¶: Denoise channel internal reference capacitance is 14.8pf

TOUCH_PAD_DENOISE_CAP_MAX = 8¶

enum touch_pad_shield_driver_t¶

Touch sensor shield channel drive capability level

Values:

TOUCH_PAD_SHIELD_DRV_L0 = 0¶: The max equivalent capacitance in shield channel is 40pf

TOUCH_PAD_SHIELD_DRV_L1¶: The max equivalent capacitance in shield channel is 80pf

TOUCH_PAD_SHIELD_DRV_L2¶: The max equivalent capacitance in shield channel is 120pf

TOUCH_PAD_SHIELD_DRV_L3¶: The max equivalent capacitance in shield channel is 160pf

TOUCH_PAD_SHIELD_DRV_L4¶: The max equivalent capacitance in shield channel is 200pf

TOUCH_PAD_SHIELD_DRV_L5¶: The max equivalent capacitance in shield channel is 240pf

TOUCH_PAD_SHIELD_DRV_L6¶: The max equivalent capacitance in shield channel is 280pf

TOUCH_PAD_SHIELD_DRV_L7¶: The max equivalent capacitance in shield channel is 320pf

TOUCH_PAD_SHIELD_DRV_MAX¶

enum touch_pad_conn_type_t¶

Touch channel idle state configuration

Values:

TOUCH_PAD_CONN_HIGHZ = 0¶: Idle status of touch channel is high resistance state

TOUCH_PAD_CONN_GND = 1¶: Idle status of touch channel is ground connection

TOUCH_PAD_CONN_MAX¶

enum touch_filter_mode_t¶

Touch channel IIR filter coefficient configuration.

Note: On ESP32S2. There is an error in the IIR calculation. The magnitude of the error is twice the filter coefficient. So please select a smaller filter coefficient on the basis of meeting the filtering requirements. Recommended filter coefficient selection IIR_16.

Values:

TOUCH_PAD_FILTER_IIR_4 = 0¶: The filter mode is first-order IIR filter. The coefficient is 4.

TOUCH_PAD_FILTER_IIR_8¶: The filter mode is first-order IIR filter. The coefficient is 8.

TOUCH_PAD_FILTER_IIR_16¶: The filter mode is first-order IIR filter. The coefficient is 16 (Typical value).

TOUCH_PAD_FILTER_IIR_32¶: The filter mode is first-order IIR filter. The coefficient is 32.

TOUCH_PAD_FILTER_IIR_64¶: The filter mode is first-order IIR filter. The coefficient is 64.

TOUCH_PAD_FILTER_IIR_128¶: The filter mode is first-order IIR filter. The coefficient is 128.

TOUCH_PAD_FILTER_IIR_256¶: The filter mode is first-order IIR filter. The coefficient is 256.

TOUCH_PAD_FILTER_JITTER¶: The filter mode is jitter filter

TOUCH_PAD_FILTER_MAX¶

enum touch_smooth_mode_t¶

Level of filter applied on the original data against large noise interference.

Note: On ESP32S2. There is an error in the IIR calculation. The magnitude of the error is twice the filter coefficient. So please select a smaller filter coefficient on the basis of meeting the filtering requirements. Recommended filter coefficient selection IIR_2.

Values:

TOUCH_PAD_SMOOTH_OFF = 0¶: No filtering of raw data.

TOUCH_PAD_SMOOTH_IIR_2 = 1¶: Filter the raw data. The coefficient is 2 (Typical value).

TOUCH_PAD_SMOOTH_IIR_4 = 2¶: Filter the raw data. The coefficient is 4.

TOUCH_PAD_SMOOTH_IIR_8 = 3¶: Filter the raw data. The coefficient is 8.

TOUCH_PAD_SMOOTH_MAX¶

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