Skip to content

Latest commit

 

History

History
128 lines (80 loc) · 4.43 KB

touch.rst

File metadata and controls

128 lines (80 loc) · 4.43 KB

TOUCH

About

Touch sensor is a peripheral, that has an internal oscilator circuit and it measures charge/discharge frequency over a fixed period of time on respective GPIO pins. Therefore these touch sensors are also known as capacitive sensors. For example, if you touch any of these pins, finger electrical charge will change this number of cycles, by changing the RC circuit attached to the touch sensor. The TouchRead() will return the number of cycles (charges/discharges) in a certain time (meas). The change of this count will be used to validate if a touch has happened or not. 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 gets the touch sensor data. Each touch sensor has a counter to count the number of charge/discharge cycles. When the pad is ‘touched’, the value in the counter will change because of the larger equivalent capacitance. The change of the data determines if the pad has been touched or not.

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. The defaults are setting touchRead to take ~0.5ms.

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

touchAttachInterrupt

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

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 the 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 the 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 the touch pad has been and continues pressed or false otherwise.

Example Applications

Example of reading the touch sensor.

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

A usage example for the touch interrupts.

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

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