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/*
* This file is part of the MicroPython project, http://micropython.org/
*
* The MIT License (MIT)
*
* Copyright (c) 2016 Scott Shawcroft for Adafruit Industries
* Copyright (c) 2018 Nick Moore for Adafruit Industries
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include <string.h>
#include <stdio.h>
#include "py/runtime.h"
#include "py/mphal.h"
#include "shared-bindings/touchio/TouchIn.h"
#include "shared-bindings/microcontroller/Pin.h"
// This is a capacitive touch sensing routine using a single digital
// pin. The pin should be connected to the sensing pad, and to ground
// via a 1Mohm or thereabout drain resistor. When a reading is taken,
// the pin's capacitance is charged by setting it to a digital output
// 'high' for a few microseconds, and then it is changed to a high
// impedance input. We measure how long it takes to discharge through
// the resistor (around 50us), using a busy-waiting loop, and average
// over N_SAMPLES cycles to reduce the effects of noise.
#define N_SAMPLES 10
#define TIMEOUT_TICKS 10000
static uint16_t get_raw_reading(touchio_touchin_obj_t *self) {
uint16_t ticks = 0;
for (uint16_t i = 0; i < N_SAMPLES; i++) {
// set pad to digital output high for 10us to charge it
common_hal_digitalio_digitalinout_switch_to_output(self->digitalinout, true, DRIVE_MODE_PUSH_PULL);
mp_hal_delay_us(10);
// set pad back to an input and take some samples
common_hal_digitalio_digitalinout_switch_to_input(self->digitalinout, PULL_NONE);
while(common_hal_digitalio_digitalinout_get_value(self->digitalinout)) {
if (ticks >= TIMEOUT_TICKS) return TIMEOUT_TICKS;
ticks++;
}
}
return ticks;
}
void common_hal_touchio_touchin_construct(touchio_touchin_obj_t* self, const mcu_pin_obj_t *pin) {
common_hal_mcu_pin_claim(pin);
self->digitalinout = m_new_obj(digitalio_digitalinout_obj_t);
self->digitalinout->base.type = &digitalio_digitalinout_type;
common_hal_digitalio_digitalinout_construct(self->digitalinout, pin);
uint16_t raw_reading = get_raw_reading(self);
if (raw_reading == TIMEOUT_TICKS) {
mp_raise_ValueError(translate("No pulldown on pin; 1Mohm recommended"));
}
self->threshold = raw_reading * 1.05 + 100;
}
bool common_hal_touchio_touchin_deinited(touchio_touchin_obj_t* self) {
return self->digitalinout == MP_OBJ_NULL;
}
void common_hal_touchio_touchin_deinit(touchio_touchin_obj_t* self) {
if (common_hal_touchio_touchin_deinited(self)) {
return;
}
common_hal_digitalio_digitalinout_deinit(self->digitalinout);
self->digitalinout = MP_OBJ_NULL;
}
void touchin_reset() {
}
bool common_hal_touchio_touchin_get_value(touchio_touchin_obj_t *self) {
uint16_t reading = get_raw_reading(self);
return reading > self->threshold;
}
uint16_t common_hal_touchio_touchin_get_raw_value(touchio_touchin_obj_t *self) {
return get_raw_reading(self);
}
uint16_t common_hal_touchio_touchin_get_threshold(touchio_touchin_obj_t *self) {
return self->threshold;
}
void common_hal_touchio_touchin_set_threshold(touchio_touchin_obj_t *self,
uint16_t new_threshold) {
self->threshold = new_threshold;
}