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