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touch.rst

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TOUCH

About

Touch sensor is a peripheral, that can be used to sense electrical changes on respective GPIO pins. Therefore these touch sensors are also known as capacitive sensors. For example, if you touch any of these pins, the touch sensor will sense output according to electrical charge on your finger. These pins can be easily integrated into capacitive pads, and replace mechanical buttons.

Note

Touch peripheral is not present in every SoC. Refer to datasheet of each chip for more info.

Arduino-ESP32 TOUCH API

TOUCH common API

touchRead

This function is used to get the TOUCH pad value for a given pin.

touch_value_t touchRead(uint8_t pin);
  • pin GPIO pin to read TOUCH value

This function will return touch pad value as uint16_t (ESP32) or uint32_t (ESP32-S2/S3).

touchSetCycles

This function is used to set cycles that measurement operation takes. The result from touchRead, threshold and detection accuracy depend on these values. Defaults are 0x1000 for measure and 0x1000 for sleep. With default values touchRead takes 0.5ms.

void touchSetCycles(uint16_t measure, uint16_t sleep);
  • measure Sets time it takes to measure touch pad value
  • sleep Sets waiting time before next measure cycle

touchAttachInterrupt

This function is used to attach interrupt to touch pad. The function will be called if a touch pad value falls below the given threshold for ESP32 / rises above the given threshold for ESP32-S2/S3. To determine a proper threshold values between touched and untouched state use touchRead.

void touchAttachInterrupt(uint8_t pin, void (*userFunc)(void), touch_value_t threshold);
  • pin GPIO TOUCH pad pin
  • userFunc Function to be called when interrupt is triggered
  • threshold Sets the threshold when to call interrupt

touchAttachInterruptArg

This function is used to attach interrupt to touch pad. In the function called by ISR you have the given arguments available.

void touchAttachInterruptArg(uint8_t pin, void (*userFunc)(void*), void *arg, touch_value_t threshold);
  • pin GPIO TOUCH pad pin
  • userFunc Function to be called when interrupt is triggered
  • arg Sets arguments to the interrupt
  • threshold Sets the threshold when to call interrupt

touchDetachInterrupt

This function is used to detach interrupt from touch pad.

void touchDetachInterrupt(uint8_t pin);
  • pin GPIO TOUCH pad pin.

TOUCH API specific for ESP32 chip (TOUCH_V1)

touchInterruptSetThresholdDirection

This function is used to tell the driver if it shall activate the interrupt if the sensor is lower or higher than the threshold value. Default is lower.

void touchInterruptSetThresholdDirection(bool mustbeLower);

TOUCH API specific for ESP32S2 and ESP32S3 chip (TOUCH_V2)

touchInterruptGetLastStatus

This function is used get the lastest ISR status for the touch pad.

bool touchInterruptGetLastStatus(uint8_t pin);

This function returns true if touch pad has been and continues pressed or false otherwise.

Example Applications

Example of reading the touch pad.

.. literalinclude:: ../../../libraries/ESP32/examples/Touch/TouchRead/TouchRead.ino
    :language: arduino

Example of usage the touch interrupts.

.. literalinclude:: ../../../libraries/ESP32/examples/Touch/TouchInterrupt/TouchInterrupt.ino
    :language: arduino

More examples can be found in our repository -> Touch examples.