Touch Sensor
Introduction
A touch sensor system is built on a substrate which carries electrodes and relevant connections under a protective flat surface. When a user touches the surface, the capacitance variation is used to evaluate if the touch was valid.
The sensing pads can be arranged in different combinations (e.g., matrix, slider), so that a larger area or more points can be detected. The touch pad sensing process is under the control of a hardware-implemented finite-state machine (FSM) which is initiated by software or a dedicated hardware timer.
For design, operation, and control registers of a touch sensor, see ESP32 Technical Reference Manual > On-Chip Sensors and Analog Signal Processing [PDF].
In-depth design details of touch sensors and firmware development guidelines for ESP32 are available in Touch Sensor Application Note.
For more information about testing touch sensors in various configurations, please check the Guide for ESP32-Sense-Kit.
Functionality Overview
Description of API is broken down into groups of functions to provide a quick overview of the following features:
Initialization of touch pad driver
Configuration of touch pad GPIO pins
Taking measurements
Adjusting parameters of measurements
Filtering measurements
Touch detection methods
Setting up interrupts to report touch detection
Waking up from Sleep mode on interrupt
For detailed description of a particular function, please go to Section API Reference. Practical implementation of this API is covered in Section Application Examples.
Initialization
Before using a touch pad, you need to initialize the touch pad driver by calling the function touch_pad_init()
. This function sets several .._DEFAULT
driver parameters listed in API Reference under Macros. It also removes the information about which pads have been touched before, if any, and disables interrupts.
If the driver is not required anymore, deinitialize it by calling touch_pad_deinit()
.
Configuration
Enabling the touch sensor functionality for a particular GPIO is done with touch_pad_config()
. The following 10 capacitive touch pads are supported for ESP32.
Touch Pad |
GPIO Pin |
---|---|
T0 |
GPIO4 |
T1 |
GPIO0 |
T2 |
GPIO2 |
T3 |
MTDO |
T4 |
MTCK |
T5 |
MTDI |
T6 |
MTMS |
T7 |
GPIO27 |
T8 |
32K_XN |
T9 |
32K_XP |
Use the function touch_pad_set_fsm_mode()
to select if touch pad measurement (operated by FSM) should be started automatically by a hardware timer, or by software. If software mode is selected, use touch_pad_sw_start()
to start the FSM.
Touch State Measurements
The following two functions come in handy to read raw or filtered measurements from the sensor:
They can also be used, for example, to evaluate a particular touch pad design by checking the range of sensor readings when a pad is touched or released. This information can be then used to establish a touch threshold.
Note
Before using touch_pad_read_filtered()
, you need to initialize and configure the filter by calling specific filter functions described in Section Filtering of Measurements.
For the demonstration of how to read the touch pad data, check the application example peripherals/touch_sensor/touch_sensor_v1/touch_pad_read.
Method of Measurements
The touch sensor will count the number of charge/discharge cycles over a fixed period of time (specified by touch_pad_set_measurement_clock_cycles()
). The count result is the raw data that read from touch_pad_read_raw_data()
. After finishing one measurement, the touch sensor will sleep until the next measurement start, this interval between two measurements can be set by touch_pad_set_measurement_interval()
.
Note
If the specified clock cycles for measurement is too samll, the result may be inaccurate, but increasing clock cycles will increase the power consumption as well. Additionally, the response of the touch sensor will slow down if the total time of the inverval and measurement is too long.
Optimization of Measurements
A touch sensor has several configurable parameters to match the characteristics of a particular touch pad design. For instance, to sense smaller capacity changes, it is possible to narrow down the reference voltage range within which the touch pads are charged / discharged. The high and low reference voltages are set using the function touch_pad_set_voltage()
.
Besides the ability to discern smaller capacity changes, a positive side effect is reduction of power consumption for low power applications. A likely negative effect is an increase in measurement noise. If the dynamic range of obtained readings is still satisfactory, then further reduction of power consumption might be done by reducing the measurement time with touch_pad_set_measurement_clock_cycles()
.
The following list summarizes available measurement parameters and corresponding 'set' functions:
Touch pad charge / discharge parameters:
voltage range:
touch_pad_set_voltage()
speed (slope):
touch_pad_set_cnt_mode()
Clock cycles of one measurement:
touch_pad_set_measurement_clock_cycles()
Relationship between the voltage range (high/low reference voltages), speed (slope), and measurement time is shown in the figure below.
The last chart Output represents the touch sensor reading, i.e., the count of pulses collected within the measurement time.
All functions are provided in pairs to set a specific parameter and to get the current parameter's value, e.g., touch_pad_set_voltage()
and touch_pad_get_voltage()
.
Filtering of Measurements
If measurements are noisy, you can filter them with provided API functions. Before using the filter, please start it by calling touch_pad_filter_start()
.
The filter type is IIR (infinite impulse response), and it has a configurable period that can be set with the function touch_pad_set_filter_period()
.
You can stop the filter with touch_pad_filter_stop()
. If not required anymore, the filter can be deleted by invoking touch_pad_filter_delete()
.
Touch Detection
Touch detection is implemented in ESP32's hardware based on the user-configured threshold and raw measurements executed by FSM. Use the functions touch_pad_get_status()
to check which pads have been touched and touch_pad_clear_status()
to clear the touch status information.
Hardware touch detection can also be wired to interrupts. This is described in the next section.
If measurements are noisy and capacity changes are small, hardware touch detection might be unreliable. To resolve this issue, instead of using hardware detection / provided interrupts, implement measurement filtering and perform touch detection in your own application. For sample implementation of both methods of touch detection, see peripherals/touch_sensor/touch_sensor_v1/touch_pad_interrupt.
Touch Triggered Interrupts
Before enabling an interrupt on a touch detection, you should establish a touch detection threshold. Use the functions described in Touch State Measurements to read and display sensor measurements when a pad is touched and released. Apply a filter if measurements are noisy and relative capacity changes are small. Depending on your application and environment conditions, test the influence of temperature and power supply voltage changes on measured values.
Once a detection threshold is established, it can be set during initialization with touch_pad_config()
or at the runtime with touch_pad_set_thresh()
.
In the next step, configure how interrupts are triggered. They can be triggered below or above the threshold, which is set with the function touch_pad_set_trigger_mode()
.
Finally, configure and manage interrupt calls using the following functions:
When interrupts are operational, you can obtain the information from which particular pad an interrupt came by invoking touch_pad_get_status()
and clear the pad status with touch_pad_clear_status()
.
Note
Interrupts on touch detection operate on raw / unfiltered measurements checked against user established threshold and are implemented in hardware. Enabling the software filtering API (see Filtering of Measurements) does not affect this process.
Wakeup from Sleep Mode
If touch pad interrupts are used to wake up the chip from a sleep mode, you can select a certain configuration of pads (SET1 or both SET1 and SET2) that should be touched to trigger the interrupt and cause the subsequent wakeup. To do so, use the function touch_pad_set_trigger_source()
.
Configuration of required bit patterns of pads may be managed for each 'SET' with:
Application Examples
Touch sensor read example: peripherals/touch_sensor/touch_sensor_v1/touch_pad_read.
Touch sensor interrupt example: peripherals/touch_sensor/touch_sensor_v1/touch_pad_interrupt.
API Reference
Header File
Functions
-
esp_err_t touch_pad_config(touch_pad_t touch_num, uint16_t threshold)
Configure touch pad interrupt threshold.
Note
If FSM mode is set to TOUCH_FSM_MODE_TIMER, this function will be blocked for one measurement cycle and wait for data to be valid.
- Parameters
touch_num -- touch pad index
threshold -- interrupt threshold,
- Returns
ESP_OK Success
ESP_ERR_INVALID_ARG if argument wrong
ESP_FAIL if touch pad not initialized
-
esp_err_t touch_pad_read(touch_pad_t touch_num, uint16_t *touch_value)
get touch sensor counter value. Each touch sensor has a counter to count the number of charge/discharge cycles. When the pad is not 'touched', we can get a number of the counter. When the pad is 'touched', the value in counter will get smaller because of the larger equivalent capacitance.
Note
This API requests hardware measurement once. If IIR filter mode is enabled, please use 'touch_pad_read_raw_data' interface instead.
- Parameters
touch_num -- touch pad index
touch_value -- pointer to accept touch sensor value
- Returns
ESP_OK Success
ESP_ERR_INVALID_ARG Touch pad parameter error
ESP_ERR_INVALID_STATE This touch pad hardware connection is error, the value of "touch_value" is 0.
ESP_FAIL Touch pad not initialized
-
esp_err_t touch_pad_read_filtered(touch_pad_t touch_num, uint16_t *touch_value)
get filtered touch sensor counter value by IIR filter.
Note
touch_pad_filter_start has to be called before calling touch_pad_read_filtered. This function can be called from ISR
- Parameters
touch_num -- touch pad index
touch_value -- pointer to accept touch sensor value
- Returns
ESP_OK Success
ESP_ERR_INVALID_ARG Touch pad parameter error
ESP_ERR_INVALID_STATE This touch pad hardware connection is error, the value of "touch_value" is 0.
ESP_FAIL Touch pad not initialized
-
esp_err_t touch_pad_read_raw_data(touch_pad_t touch_num, uint16_t *touch_value)
get raw data (touch sensor counter value) from IIR filter process. Need not request hardware measurements.
Note
touch_pad_filter_start has to be called before calling touch_pad_read_raw_data. This function can be called from ISR
- Parameters
touch_num -- touch pad index
touch_value -- pointer to accept touch sensor value
- Returns
ESP_OK Success
ESP_ERR_INVALID_ARG Touch pad parameter error
ESP_ERR_INVALID_STATE This touch pad hardware connection is error, the value of "touch_value" is 0.
ESP_FAIL Touch pad not initialized
-
esp_err_t touch_pad_set_filter_read_cb(filter_cb_t read_cb)
Register the callback function that is called after each IIR filter calculation.
Note
The 'read_cb' callback is called in timer task in each filtering cycle.
- Parameters
read_cb -- Pointer to filtered callback function. If the argument passed in is NULL, the callback will stop.
- Returns
ESP_OK Success
ESP_ERR_INVALID_ARG set error
-
esp_err_t touch_pad_isr_register(intr_handler_t fn, void *arg)
Register touch-pad ISR. The handler will be attached to the same CPU core that this function is running on.
- Parameters
fn -- Pointer to ISR handler
arg -- Parameter for ISR
- Returns
ESP_OK Success ;
ESP_ERR_INVALID_ARG GPIO error
ESP_ERR_NO_MEM No memory
-
esp_err_t touch_pad_set_measurement_clock_cycles(uint16_t clock_cycle)
Set the clock cycles of each measurement.
Note
This function will specify the clock cycles of each measurement and the clock is sourced from SOC_MOD_CLK_RTC_FAST, its default frequency is SOC_CLK_RC_FAST_FREQ_APPROX The touch sensor will record the charge and discharge times during these clock cycles as the final result (raw value)
Note
If clock cyles is too small, it may lead to inaccurate results.
- Parameters
clock_cycle -- The clock cycles of each measurement measure_time = clock_cycle / SOC_CLK_RC_FAST_FREQ_APPROX, the maximum measure time is 0xffff / SOC_CLK_RC_FAST_FREQ_APPROX
- Returns
ESP_OK Set the clock cycle success
-
esp_err_t touch_pad_get_measurement_clock_cycles(uint16_t *clock_cycle)
Get the clock cycles of each measurement.
- Parameters
clock_cycle -- The clock cycles of each measurement
- Returns
ESP_OK Get the clock cycle success
ESP_ERR_INVALID_ARG The input parameter is NULL
-
esp_err_t touch_pad_set_measurement_interval(uint16_t interval_cycle)
Set the interval between two measurements.
Note
The touch sensor will sleep between two mesurements This function is to set the interval cycle And the interval is clocked from SOC_MOD_CLK_RTC_SLOW, its default frequency is SOC_CLK_RC_SLOW_FREQ_APPROX
- Parameters
interval_cycle -- The interval between two measurements sleep_time = interval_cycle / SOC_CLK_RC_SLOW_FREQ_APPROX. The approximate frequency value of RTC_SLOW_CLK can be obtained using rtc_clk_slow_freq_get_hz function.
- Returns
ESP_OK Set interval cycle success
-
esp_err_t touch_pad_get_measurement_interval(uint16_t *interval_cycle)
Get the interval between two measurements.
- Parameters
interval_cycle -- The interval between two measurements
- Returns
ESP_OK Get interval cycle success
ESP_ERR_INVALID_ARG The input parameter is NULL
-
esp_err_t touch_pad_set_meas_time(uint16_t sleep_cycle, uint16_t meas_cycle)
Set touch sensor measurement 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 touch sensor will count the number of charge/discharge cycles over a fixed period of time (specified as the second parameter). That means the number of cycles (raw value) will decrease as the capacity of the touch pad is increasing.
Note
The greater the duty cycle of the measurement time, the more system power is consumed.
- Parameters
sleep_cycle -- The touch sensor will sleep after each measurement. sleep_cycle decide the interval between each measurement. t_sleep = sleep_cycle / SOC_CLK_RC_SLOW_FREQ_APPROX. The approximate frequency value of RTC_SLOW_CLK can be obtained using rtc_clk_slow_freq_get_hz function.
meas_cycle -- The duration of the touch sensor measurement. t_meas = meas_cycle / SOC_CLK_RC_FAST_FREQ_APPROX, the maximum measure time is 0xffff / SOC_CLK_RC_FAST_FREQ_APPROX
- Returns
ESP_OK on success
-
esp_err_t touch_pad_get_meas_time(uint16_t *sleep_cycle, uint16_t *meas_cycle)
Get touch sensor measurement and sleep time.
- Parameters
sleep_cycle -- Pointer to accept sleep cycle number
meas_cycle -- Pointer to accept measurement cycle count.
- Returns
ESP_OK on success
ESP_ERR_INVALID_ARG The input parameter is NULL
-
esp_err_t touch_pad_sw_start(void)
Trigger a touch sensor measurement, only support in SW mode of FSM.
- Returns
ESP_OK on success
-
esp_err_t touch_pad_set_thresh(touch_pad_t touch_num, uint16_t threshold)
Set touch sensor interrupt threshold.
- Parameters
touch_num -- touch pad index
threshold -- threshold of touchpad count, refer to touch_pad_set_trigger_mode to see how to set trigger mode.
- Returns
ESP_OK on success
ESP_ERR_INVALID_ARG if argument is wrong
-
esp_err_t touch_pad_get_thresh(touch_pad_t touch_num, uint16_t *threshold)
Get touch sensor interrupt threshold.
- Parameters
touch_num -- touch pad index
threshold -- pointer to accept threshold
- Returns
ESP_OK on success
ESP_ERR_INVALID_ARG if argument is wrong
-
esp_err_t touch_pad_set_trigger_mode(touch_trigger_mode_t mode)
Set touch sensor interrupt trigger mode. Interrupt can be triggered either when counter result is less than threshold or when counter result is more than threshold.
- Parameters
mode -- touch sensor interrupt trigger mode
- Returns
ESP_OK on success
ESP_ERR_INVALID_ARG if argument is wrong
-
esp_err_t touch_pad_get_trigger_mode(touch_trigger_mode_t *mode)
Get touch sensor interrupt trigger mode.
- Parameters
mode -- pointer to accept touch sensor interrupt trigger mode
- Returns
ESP_OK on success
-
esp_err_t touch_pad_set_trigger_source(touch_trigger_src_t src)
Set touch sensor interrupt trigger source. There are two sets of touch signals. Set1 and set2 can be mapped to several touch signals. Either set will be triggered if at least one of its touch signal is 'touched'. The interrupt can be configured to be generated if set1 is triggered, or only if both sets are triggered.
- Parameters
src -- touch sensor interrupt trigger source
- Returns
ESP_OK on success
ESP_ERR_INVALID_ARG if argument is wrong
-
esp_err_t touch_pad_get_trigger_source(touch_trigger_src_t *src)
Get touch sensor interrupt trigger source.
- Parameters
src -- pointer to accept touch sensor interrupt trigger source
- Returns
ESP_OK on success
-
esp_err_t touch_pad_set_group_mask(uint16_t set1_mask, uint16_t set2_mask, uint16_t en_mask)
Set touch sensor group mask. Touch pad module has two sets of signals, 'Touched' signal is triggered only if at least one of touch pad in this group is "touched". This function will set the register bits according to the given bitmask.
- Parameters
set1_mask -- bitmask of touch sensor signal group1, it's a 10-bit value
set2_mask -- bitmask of touch sensor signal group2, it's a 10-bit value
en_mask -- bitmask of touch sensor work enable, it's a 10-bit value
- Returns
ESP_OK on success
ESP_ERR_INVALID_ARG if argument is wrong
-
esp_err_t touch_pad_get_group_mask(uint16_t *set1_mask, uint16_t *set2_mask, uint16_t *en_mask)
Get touch sensor group mask.
- Parameters
set1_mask -- pointer to accept bitmask of touch sensor signal group1, it's a 10-bit value
set2_mask -- pointer to accept bitmask of touch sensor signal group2, it's a 10-bit value
en_mask -- pointer to accept bitmask of touch sensor work enable, it's a 10-bit value
- Returns
ESP_OK on success
-
esp_err_t touch_pad_clear_group_mask(uint16_t set1_mask, uint16_t set2_mask, uint16_t en_mask)
Clear touch sensor group mask. Touch pad module has two sets of signals, Interrupt is triggered only if at least one of touch pad in this group is "touched". This function will clear the register bits according to the given bitmask.
- Parameters
set1_mask -- bitmask touch sensor signal group1, it's a 10-bit value
set2_mask -- bitmask touch sensor signal group2, it's a 10-bit value
en_mask -- bitmask of touch sensor work enable, it's a 10-bit value
- Returns
ESP_OK on success
ESP_ERR_INVALID_ARG if argument is wrong
-
esp_err_t touch_pad_set_filter_period(uint32_t new_period_ms)
set touch pad filter calibration period, in ms. Need to call touch_pad_filter_start before all touch filter APIs
- Parameters
new_period_ms -- filter period, in ms
- Returns
ESP_OK Success
ESP_ERR_INVALID_STATE driver state error
ESP_ERR_INVALID_ARG parameter error
-
esp_err_t touch_pad_get_filter_period(uint32_t *p_period_ms)
get touch pad filter calibration period, in ms Need to call touch_pad_filter_start before all touch filter APIs
- Parameters
p_period_ms -- pointer to accept period
- Returns
ESP_OK Success
ESP_ERR_INVALID_STATE driver state error
ESP_ERR_INVALID_ARG parameter error
-
esp_err_t touch_pad_filter_start(uint32_t filter_period_ms)
start touch pad filter function This API will start a filter to process the noise in order to prevent false triggering when detecting slight change of capacitance. Need to call touch_pad_filter_start before all touch filter APIs
Note
This filter uses FreeRTOS timer, which is dispatched from a task with priority 1 by default on CPU 0. So if some application task with higher priority takes a lot of CPU0 time, then the quality of data obtained from this filter will be affected. You can adjust FreeRTOS timer task priority in menuconfig.
- Parameters
filter_period_ms -- filter calibration period, in ms
- Returns
ESP_OK Success
ESP_ERR_INVALID_ARG parameter error
ESP_ERR_NO_MEM No memory for driver
ESP_ERR_INVALID_STATE driver state error
Type Definitions
-
typedef void (*filter_cb_t)(uint16_t *raw_value, uint16_t *filtered_value)
Callback function that is called after each IIR filter calculation.
Note
This callback is called in timer task in each filtering cycle.
Note
This callback should not be blocked.
- Param raw_value
The latest raw data(touch sensor counter value) that points to all channels(raw_value[0..TOUCH_PAD_MAX-1]).
- Param filtered_value
The latest IIR filtered data(calculated from raw data) that points to all channels(filtered_value[0..TOUCH_PAD_MAX-1]).
Header File
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.
- Returns
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.
- Returns
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.
- Parameters
touch_num -- touch pad index
- Returns
ESP_OK on success
ESP_ERR_INVALID_ARG if argument is wrong
-
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.
- Parameters
refh -- the value of DREFH
refl -- the value of DREFL
atten -- the attenuation on DREFH
- Returns
ESP_OK on success
ESP_ERR_INVALID_ARG if argument is wrong
-
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,.
- Parameters
refh -- pointer to accept DREFH value
refl -- pointer to accept DREFL value
atten -- pointer to accept the attenuation on DREFH
- Returns
ESP_OK on success
-
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.
- Parameters
touch_num -- touch pad index
slope -- touch pad charge/discharge speed
opt -- the initial voltage
- Returns
ESP_OK on success
ESP_ERR_INVALID_ARG if argument is wrong
-
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.
- Parameters
touch_num -- touch pad index
slope -- pointer to accept touch pad charge/discharge slope
opt -- pointer to accept the initial voltage
- Returns
ESP_OK on success
ESP_ERR_INVALID_ARG if argument is wrong
-
esp_err_t touch_pad_isr_deregister(void (*fn)(void*), void *arg)
Deregister the handler previously registered using touch_pad_isr_handler_register.
- 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)
- Returns
ESP_OK on success
ESP_ERR_INVALID_STATE if a handler matching both fn and arg isn't registered
-
esp_err_t touch_pad_get_wakeup_status(touch_pad_t *pad_num)
Get the touch pad which caused wakeup from deep sleep.
- Parameters
pad_num -- pointer to touch pad which caused wakeup
- Returns
ESP_OK Success
ESP_ERR_INVALID_ARG parameter is NULL
-
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.
- Parameters
mode -- FSM mode
- Returns
ESP_OK on success
ESP_ERR_INVALID_ARG if argument is wrong
-
esp_err_t touch_pad_get_fsm_mode(touch_fsm_mode_t *mode)
Get touch sensor FSM mode.
- Parameters
mode -- pointer to accept FSM mode
- Returns
ESP_OK on success
-
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.
- Returns
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.
- Returns
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.
- Returns
True measurement is under way
False measurement done
GPIO Lookup Macros
Some useful macros can be used to specified the GPIO number of a touch pad channel, or vice versa. e.g.
TOUCH_PAD_NUM5_GPIO_NUM
is the GPIO number of channel 5 (12);TOUCH_PAD_GPIO4_CHANNEL
is the channel number of GPIO 4 (channel 0).
Header File
Macros
-
TOUCH_PAD_GPIO4_CHANNEL
-
TOUCH_PAD_NUM0_GPIO_NUM
-
TOUCH_PAD_GPIO0_CHANNEL
-
TOUCH_PAD_NUM1_GPIO_NUM
-
TOUCH_PAD_GPIO2_CHANNEL
-
TOUCH_PAD_NUM2_GPIO_NUM
-
TOUCH_PAD_GPIO15_CHANNEL
-
TOUCH_PAD_NUM3_GPIO_NUM
-
TOUCH_PAD_GPIO13_CHANNEL
-
TOUCH_PAD_NUM4_GPIO_NUM
-
TOUCH_PAD_GPIO12_CHANNEL
-
TOUCH_PAD_NUM5_GPIO_NUM
-
TOUCH_PAD_GPIO14_CHANNEL
-
TOUCH_PAD_NUM6_GPIO_NUM
-
TOUCH_PAD_GPIO27_CHANNEL
-
TOUCH_PAD_NUM7_GPIO_NUM
-
TOUCH_PAD_GPIO33_CHANNEL
-
TOUCH_PAD_NUM8_GPIO_NUM
-
TOUCH_PAD_GPIO32_CHANNEL
-
TOUCH_PAD_NUM9_GPIO_NUM
Header File
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
The timer frequency is RTC_SLOW_CLK (can be 150k or 32k depending on the options), max value is 0xffff
-
TOUCH_PAD_MEASURE_CYCLE_DEFAULT
The timer frequency is 8Mhz, the max value is 0x7fff
-
TOUCH_FSM_MODE_DEFAULT
The touch FSM my be started by the software or timer
-
TOUCH_TRIGGER_MODE_DEFAULT
Interrupts can be triggered if sensor value gets below or above threshold
-
TOUCH_TRIGGER_SOURCE_DEFAULT
The wakeup trigger source can be SET1 or both SET1 and SET2
Enumerations
-
enum touch_pad_t
Touch pad channel
Values:
-
enumerator TOUCH_PAD_NUM0
Touch pad channel 0 is GPIO4(ESP32)
-
enumerator TOUCH_PAD_NUM1
Touch pad channel 1 is GPIO0(ESP32) / GPIO1(ESP32-S2)
-
enumerator TOUCH_PAD_NUM2
Touch pad channel 2 is GPIO2(ESP32) / GPIO2(ESP32-S2)
-
enumerator TOUCH_PAD_NUM3
Touch pad channel 3 is GPIO15(ESP32) / GPIO3(ESP32-S2)
-
enumerator TOUCH_PAD_NUM4
Touch pad channel 4 is GPIO13(ESP32) / GPIO4(ESP32-S2)
-
enumerator TOUCH_PAD_NUM5
Touch pad channel 5 is GPIO12(ESP32) / GPIO5(ESP32-S2)
-
enumerator TOUCH_PAD_NUM6
Touch pad channel 6 is GPIO14(ESP32) / GPIO6(ESP32-S2)
-
enumerator TOUCH_PAD_NUM7
Touch pad channel 7 is GPIO27(ESP32) / GPIO7(ESP32-S2)
-
enumerator TOUCH_PAD_NUM8
Touch pad channel 8 is GPIO33(ESP32) / GPIO8(ESP32-S2)
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enumerator TOUCH_PAD_NUM9
Touch pad channel 9 is GPIO32(ESP32) / GPIO9(ESP32-S2)
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enumerator TOUCH_PAD_MAX
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enumerator TOUCH_PAD_NUM0
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enum touch_high_volt_t
Touch sensor high reference voltage
Values:
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enumerator TOUCH_HVOLT_KEEP
Touch sensor high reference voltage, no change
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enumerator TOUCH_HVOLT_2V4
Touch sensor high reference voltage, 2.4V
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enumerator TOUCH_HVOLT_2V5
Touch sensor high reference voltage, 2.5V
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enumerator TOUCH_HVOLT_2V6
Touch sensor high reference voltage, 2.6V
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enumerator TOUCH_HVOLT_2V7
Touch sensor high reference voltage, 2.7V
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enumerator TOUCH_HVOLT_MAX
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enumerator TOUCH_HVOLT_KEEP
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enum touch_low_volt_t
Touch sensor low reference voltage
Values:
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enumerator TOUCH_LVOLT_KEEP
Touch sensor low reference voltage, no change
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enumerator TOUCH_LVOLT_0V5
Touch sensor low reference voltage, 0.5V
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enumerator TOUCH_LVOLT_0V6
Touch sensor low reference voltage, 0.6V
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enumerator TOUCH_LVOLT_0V7
Touch sensor low reference voltage, 0.7V
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enumerator TOUCH_LVOLT_0V8
Touch sensor low reference voltage, 0.8V
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enumerator TOUCH_LVOLT_MAX
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enumerator TOUCH_LVOLT_KEEP
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enum touch_volt_atten_t
Touch sensor high reference voltage attenuation
Values:
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enumerator TOUCH_HVOLT_ATTEN_KEEP
Touch sensor high reference voltage attenuation, no change
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enumerator TOUCH_HVOLT_ATTEN_1V5
Touch sensor high reference voltage attenuation, 1.5V attenuation
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enumerator TOUCH_HVOLT_ATTEN_1V
Touch sensor high reference voltage attenuation, 1.0V attenuation
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enumerator TOUCH_HVOLT_ATTEN_0V5
Touch sensor high reference voltage attenuation, 0.5V attenuation
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enumerator TOUCH_HVOLT_ATTEN_0V
Touch sensor high reference voltage attenuation, 0V attenuation
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enumerator TOUCH_HVOLT_ATTEN_MAX
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enumerator TOUCH_HVOLT_ATTEN_KEEP
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enum touch_cnt_slope_t
Touch sensor charge/discharge speed
Values:
-
enumerator TOUCH_PAD_SLOPE_0
Touch sensor charge / discharge speed, always zero
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enumerator TOUCH_PAD_SLOPE_1
Touch sensor charge / discharge speed, slowest
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enumerator TOUCH_PAD_SLOPE_2
Touch sensor charge / discharge speed
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enumerator TOUCH_PAD_SLOPE_3
Touch sensor charge / discharge speed
-
enumerator TOUCH_PAD_SLOPE_4
Touch sensor charge / discharge speed
-
enumerator TOUCH_PAD_SLOPE_5
Touch sensor charge / discharge speed
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enumerator TOUCH_PAD_SLOPE_6
Touch sensor charge / discharge speed
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enumerator TOUCH_PAD_SLOPE_7
Touch sensor charge / discharge speed, fast
-
enumerator TOUCH_PAD_SLOPE_MAX
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enumerator TOUCH_PAD_SLOPE_0
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enum touch_tie_opt_t
Touch sensor initial charge level
Values:
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enumerator TOUCH_PAD_TIE_OPT_LOW
Initial level of charging voltage, low level
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enumerator TOUCH_PAD_TIE_OPT_HIGH
Initial level of charging voltage, high level
-
enumerator TOUCH_PAD_TIE_OPT_MAX
-
enumerator TOUCH_PAD_TIE_OPT_LOW
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enum touch_fsm_mode_t
Touch sensor FSM mode
Values:
-
enumerator TOUCH_FSM_MODE_TIMER
To start touch FSM by timer
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enumerator TOUCH_FSM_MODE_SW
To start touch FSM by software trigger
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enumerator TOUCH_FSM_MODE_MAX
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enumerator TOUCH_FSM_MODE_TIMER