ESP32Touch

ESP32 touch button driver for the Arduino framework using async callback interface

Example usage

File: src/examples/esp32_touch_example.cpp

HTML class documentation

File: doc/html/class_e_s_p32_touch.html

Members	Descriptions
class ESP32Touch	ESP32 touch button driver with async callback interface.

class ESP32Touch

ESP32 touch button driver with async callback interface.

This configures the hardware capacitive touch input pins on the Espressif ESP32 platform for up to ten non-multiplexed buttons.

All of the operation takes place asynchronously via user-defined callback functions, which can be any type compatible with a C++ std::function object, i.e. plain global functions, static an non-static class or instance members or C++11 lambda expressions.

In contrast to the original Arduino touchRead() function, this implementation works reliably with stable, filtered sensor readout and without false triggers by random spikes/zeros from some hardware or API failure (See: https://forum.arduino.cc/index.php?topic=629955.0)

This API uses the ESP-IDF touch sensor interface, but does not register with the touch hardware ISR interface. Instead, this uses the continuous output from the ESP-IDF touch IIR filter using the filter_read_cb() hook from touch_pad.h. A freeRTOS timer (via Ticker.h) is then set up periodicly calling an event loop handler checking if any button threshold level is reached. If this is the case, it then calls the respective user callback. This has the advantage of not blocking the filter ISR for extended time.

The cycle time for the event checking loop can be configured in the header via dispatch_cycle_time_ms setting, the default is 100 milliseconds.

For the sensor input pins, please again note that the touch API uses a different numbering scheme than the standard GPIO numbers. E.g. touch button no. 0 is GPIO 4.

Repository at: https://github.com/ul-gh/ESP32Touch 2020-02-25 Ulrich Lukas

Summary

Members	Descriptions
public ESP32Touch()
public virtual ~ESP32Touch()
public void configure_input(const int input_number,const uint8_t threshold_percent,CallbackT callback)	Configure input pin as a touch input, set threshold value and register the required user callback called when pin is touched.
public void calibrate_thresholds()	Force a sensor re-calibration.
public void begin()	This must be called once after all the user callbacks have been set up.
public void diagnostics()	Call this periodicly to see the raw sensor readout values printed.

Members

public ESP32Touch()

public virtual ~ESP32Touch()

public void configure_input(const int input_number,const uint8_t threshold_percent,CallbackT callback)

Configure input pin as a touch input, set threshold value and register the required user callback called when pin is touched.

Parameters

• input_number Touch input pin number (!) different from GPIO numbering (!)

• threshold_percent Touch button touch detection threshold in percent of the calibration-time (i.e. idle-state) sensor readout value.

• callback User callback function, which can be any type compatible with a C++ std::function object, i.e. plain global functions, static an non-static class or instance members or C++11 lambda expressions. The callback must have a signature of void(void).

public void calibrate_thresholds()

Force a sensor re-calibration.

This is called implicitly by ESP32Touch::begin(), but can be called later at run-time to do a re-calibration.

The touch buttons must not be pressed down while the calibration is running..

public void begin()

This must be called once after all the user callbacks have been set up.

public void diagnostics()

Call this periodicly to see the raw sensor readout values printed.

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