1 files changed, 118 insertions, 0 deletions
diff --git a/circuitpython/shared-module/touchio/TouchIn.c b/circuitpython/shared-module/touchio/TouchIn.c
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+++ b/circuitpython/shared-module/touchio/TouchIn.c
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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;
+}