ESP32 touch sensor

Github Repo C Header C source JS source
mongoose-os-libs/esp32-touchpad   api_esp32_touchpad.js

Overview

This library provides JavaScript bindings for the ESP32 touch pad sensor. The JS API largely mirrors the C API.

Examples

Polling the sensor manually

load('api_esp32_touchpad.js');

// Touch sensors are numbered from 0 to 9.
// For convenience, TouchPad.GPIO map translates from GPIO number to sensor number.
let ts = TouchPad.GPIO[15];

TouchPad.init();
TouchPad.setVoltage(TouchPad.HVOLT_2V4, TouchPad.LVOLT_0V8, TouchPad.HVOLT_ATTEN_1V5);
TouchPad.config(ts, 0);
Timer.set(1000 /* 1 sec */, Timer.REPEAT, function() {
  let tv = TouchPad.read(ts);
  print('Sensor', ts, 'value', tv);
}, null);

Using interrupts

load('api_esp32_touchpad.js');

// Touch sensors are numbered from 0 to 9.
// For convenience, TouchPad.GPIO map translates from GPIO number to sensor number.
let ts = TouchPad.GPIO[15];

TouchPad.init();
TouchPad.filterStart(10);
TouchPad.setMeasTime(0x1000, 0xffff);
TouchPad.setVoltage(TouchPad.HVOLT_2V4, TouchPad.LVOLT_0V8, TouchPad.HVOLT_ATTEN_1V5);
TouchPad.config(ts, 0);
Sys.usleep(100000); // wait a bit for initial filtering.
let noTouchVal = TouchPad.readFiltered(ts);
let touchThresh = noTouchVal * 2 / 3;
print('Sensor', ts, 'noTouchVal', noTouchVal, 'touchThresh', touchThresh);
TouchPad.setThresh(ts, touchThresh);
TouchPad.isrRegister(function(st) {
  // st is a bitmap with 1 bit per sensor.
  let val = TouchPad.readFiltered(ts);
  print('Status:', st, 'Value:', val);
}, null);
TouchPad.intrEnable();

JS API


TouchPad.GPIO

TouchPad.GPIO

Handy map of GPIO to touch sensor number. Touch sensor number is a number from 0 to 9.

TouchPad.init

TouchPad.init()

Initialize touch pad module. Return value: 0 in case of success, non-zero otherwise.

TouchPad.deinit

TouchPad.deinit()

Uninstall touch pad driver. Return value: 0 in case of success, non-zero otherwise.

TouchPad.config

TouchPad.config(touch_num, threshold)

Configure touch pad interrupt threshold. touch_num is a touchpad index (a number from 0 to 9), threshold is an interrupt threshold Return value: 0 in case of success, non-zero otherwise.

TouchPad.read

TouchPad.read(touch_num)

Return touch sensor counter value or -1 in case of a failure. touch_num is a touchpad index (a number from 0 to 9)

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. User can use this function to determine the interrupt trigger threshold.

TouchPad.readFiltered

TouchPad.readFiltered(touch_num)

Get filtered touch sensor counter value by IIR filter, or -1 in case of a failure. NOTE: TouchPad.filterStart() has to be called before this function. touch_num is a touchpad index (a number from 0 to 9).

TouchPad.isrRegister

TouchPad.isrRegister(handler, userdata)

Register touchpad ISR. The handler will be attached to the same CPU core that this function is running on. Handler is a function like function(status, userdata){ /* ... */ }, status is a number representing which pads are "touched". Return value: 0 in case of success, non-zero otherwise.

TouchPad.isrDeregister

TouchPad.isrDeregister()

Deregister touchpad ISR previously registered with TouchPad.isrRegister(). Return value: 0 in case of success, non-zero otherwise.

TouchPad.intrEnable

TouchPad.intrEnable()

Enable touchpad interrupt. Return value: 0.

TouchPad.intrDisable

TouchPad.intrDisable()

Disable touchpad interrupt. Return value: 0.

TouchPad.setMeasTime

TouchPad.setMeasTime(sleep_cycle, meas_cycle)

Set touch sensor measurement and sleep time. The touch sensor will sleep after each measurement. sleep_cycle determines the interval between each measurement: t_sleep = sleep_cycle / (RTC_SLOW_CLK frequency). meas_cycle is the duration of the touch sensor measurement. t_meas = meas_cycle / 8M, the maximum measure time is 0xffff / 8M = 8.19 ms Return value: 0 in case of success, non-zero otherwise.

TouchPad.getMeasTimeSleepCycle

TouchPad.getMeasTimeSleepCycle()

Return sleep cycle (previously set with TouchPad.setMeasTime()), or -1 in case of a failure.

TouchPad.getMeasTimeMeasCycle

TouchPad.getMeasTimeMeasCycle()

Return duration of the touch sensor measurement (previously set with TouchPad.setMeasTime()), or -1 in case of a failure.

TouchPad.setVoltage

TouchPad.setVoltage(refh, refl, atten)

Set touch sensor reference voltage, if the voltage gap between high and low reference voltage get less, the charging and discharging time would be faster; accordingly, the counter value would be larger. In the case of detecting very slight change of capacitance, we can narrow down the gap so as to increase the sensitivity. On the other hand, narrow voltage gap would also introduce more noise, but we can use a software filter to pre-process the counter value.

refh is the value of DREFH, one of the following:

  • TouchPad.HVOLT_KEEP
  • TouchPad.HVOLT_2V4
  • TouchPad.HVOLT_2V5
  • TouchPad.HVOLT_2V6
  • TouchPad.HVOLT_2V7

refl is the value os DREFL, one of the following:

  • TouchPad.LVOLT_KEEP
  • TouchPad.LVOLT_0V5
  • TouchPad.LVOLT_0V6
  • TouchPad.LVOLT_0V7
  • TouchPad.LVOLT_0V8

atten is the attenuation of DREFH, one of the following:

  • TouchPad.HVOLT_ATTEN_KEEP
  • TouchPad.HVOLT_ATTEN_1V5
  • TouchPad.HVOLT_ATTEN_1V
  • TouchPad.HVOLT_ATTEN_0V5
  • TouchPad.HVOLT_ATTEN_0V

Return value: 0 in case of success, non-zero otherwise.

TouchPad.getVoltageRefH

TouchPad.getVoltageRefH()

Get touch sensor reference voltage refh (previously set with TouchPad.setVoltage()), or -1 in case of a failure.

TouchPad.getVoltageRefL

TouchPad.getVoltageRefL()

Get touch sensor reference voltage refl (previously set with TouchPad.setVoltage()), or -1 in case of a failure.

TouchPad.getVoltageAtten

TouchPad.getVoltageAtten()

Get touch sensor attenuation of DREFH (previously set with TouchPad.setVoltage()), or -1 in case of a failure.

TouchPad.setCntMode

TouchPad.setCntMode(touch_num, slope, opt)

Set touch sensor charge/discharge speed for each pad.

touch_num is a touchpad index (a number from 0 to 9), slope is a charge/discharge speed, opt is the initial voltage, one of the following:

  • TouchPad.PAD_TIE_OPT_LOW
  • TouchPad.PAD_TIE_OPT_HIGH

If slope is 0, the counter would always be zero. If slope is 1, the charging and discharging would be slow, accordingly, the counter value would be small. If slope is set 7, which is the maximum value, the charging and discharging would be fast, accordingly, the counter value would be larger. Return value: 0 in case of success, non-zero otherwise.

TouchPad.getCntModeSlope

TouchPad.getCntModeSlope(touch_num)

Get "slope": a charge/discharge speed previously set with TouchPad.setCntMode(), or -1 in case of a failure.

TouchPad.getCntModeOpt

TouchPad.getCntModeOpt(touch_num)

Get initial voltage previously set with TouchPad.setCntMode(), or -1 in case of a failure. touch_num is a touchpad index (a number from 0 to 9).

TouchPad.ioInit

TouchPad.ioInit(touch_num)

Initialize touch pad GPIO. touch_num is a touchpad index (a number from 0 to 9). Return value: 0 in case of success, non-zero otherwise.

TouchPad.setFSMMode

TouchPad.setFSMMode(mode)

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

  • TouchPad.FSM_MODE_TIMER
  • TouchPad.FSM_MODE_SW Return value: 0 in case of success, non-zero otherwise.

    TouchPad.getFSMMode

TouchPad.getFSMMode()

Get FSM mode previously set with TouchPad.setFSMMode(), or -1 in case of a failure.

TouchPad.swStart

TouchPad.swStart()

Trigger a touch sensor measurement, only support in FSM_MODE_SW mode of FSM. Return value: 0 in case of success, non-zero otherwise.

TouchPad.setThresh

TouchPad.setThresh(touch_num, threshold)

Set touch sensor interrupt threshold. touch_num is a touchpad index (a number from 0 to 9), threshold is a threshold of touchpad count; refer to TouchPad.setTriggerMode() to see how to set trigger mode. Return value: 0 in case of success, non-zero otherwise.

TouchPad.getThresh

TouchPad.getThresh(touch_num)

Get touch sensor interrupt threshold previously set with TouchPad.setThresh(), or -1 in case of a failure. touch_num is a touchpad index (a number from 0 to 9). Return value: 0 in case of success, non-zero otherwise.

TouchPad.setTriggerMode

TouchPad.setTriggerMode(mode)

Set touch sensor interrupt trigger mode, one of the following:

  • TouchPad.TRIGGER_BELOW
  • TouchPad.TRIGGER_ABOVE

Interrupt can be triggered either when counter result is less than threshold, or when counter result is more than threshold.

Return value: 0 in case of success, non-zero otherwise.

TouchPad.getTriggerMode

TouchPad.getTriggerMode()

Get touch sensor interrupt trigger mode previously set with TouchPad.setTriggerMode(), or -1 in case of a failure. Return value: 0 in case of success, non-zero otherwise.

TouchPad.setTriggerSource

TouchPad.setTriggerSource(src)

Set touch sensor interrupt trigger source src, one of the following:

  • TouchPad.TRIGGER_SOURCE_BOTH
  • TouchPad.TRIGGER_SOURCE_SET1

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.

Return value: 0 in case of success, non-zero otherwise.

TouchPad.getTriggerSource

TouchPad.getTriggerSource()

Get touch sensor interrupt trigger source previously set with TouchPad.setTriggerSource(), or -1 in case of a failure. Return value: 0 in case of success, non-zero otherwise.

TouchPad.setGroupMask

TouchPad.setGroupMask(set1_mask, set2_mask, 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.

set1_mask is a bitmask of touch sensor signal group1, it's a 10-bit value. set2_mask is a bitmask of touch sensor signal group2, it's a 10-bit value. en_mask is a bitmask of touch sensor work enable, it's a 10-bit value.

Return value: 0 in case of success, non-zero otherwise.

TouchPad.getGroupMaskSet1

TouchPad.getGroupMaskSet1()

Get set1 mask previously set with TouchPad.setGroupMask(), or -1 in case of a failure.

TouchPad.getGroupMaskSet2

TouchPad.getGroupMaskSet2()

Get set2 mask previously set with TouchPad.setGroupMask(), or -1 in case of a failure.

TouchPad.getGroupMaskEn

TouchPad.getGroupMaskEn()

Get mask of enabled sensors previously set with TouchPad.setGroupMask(), or -1 in case of a failure.

TouchPad.clearStatus

TouchPad.clearStatus()

Clear touch status register. Return value: 0 in case of success, non-zero otherwise.

TouchPad.getStatus

TouchPad.getStatus()

Return status: a number representing which pads are "touched".

TouchPad.setFilterPeriod

TouchPad.setFilterPeriod(period_ms)

Set touch pad filter calibration period, in ms. Need to call TouchPad.filterStart() before all touch filter APIs. Return value: 0 in case of success, non-zero otherwise.

TouchPad.getFilterPeriod

TouchPad.getFilterPeriod(period_ms)

Get touch pad filter calibration period in ms previously set with TouchPad.setFilterPeriod(), or -1 in case of a failure.

TouchPad.filterStart

TouchPad.filterStart(filter_period_ms)

Start a filter to process the noise in order to prevent false triggering when detecting slight change of capacitance. This function must be called before any other filter API functions.

If filter is not initialized, this function will initialize the filter with given period. If filter is already initialized, it will update the filter period.

Return value: 0 in case of success, non-zero otherwise.

TouchPad.filterStop

TouchPad.filterStop()

Stop touch pad filter, started before with TouchPad.filterStart(). Return value: 0 in case of success, non-zero otherwise.

TouchPad.filterDelete

TouchPad.filterDelete()

Delete touch pad filter driver (activated before with TouchPad.filterStart()) and release the memory. Return value: 0 in case of success, non-zero otherwise.

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