text: /*
   * This file is part of the Micro Python project, http://micropython.org/
   *
   * The MIT License (MIT)
   *
   * Copyright (c) 2021 Dan Halbert 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 "py/gc.h"
  #include "py/runtime.h"
  #include "shared-bindings/digitalio/DigitalInOut.h"
  #include "shared-bindings/keypad/EventQueue.h"
  #include "shared-bindings/keypad/ShiftRegisterKeys.h"
  #include "shared-bindings/keypad/__init__.h"
  #include "shared-bindings/supervisor/__init__.h"
  #include "supervisor/port.h"
  #include "supervisor/shared/tick.h"
  
  void common_hal_keypad_shiftregisterkeys_construct(keypad_shiftregisterkeys_obj_t *self, const mcu_pin_obj_t *clock_pin, const mcu_pin_obj_t *data_pin, const mcu_pin_obj_t *latch_pin, bool value_to_latch, size_t key_count, bool value_when_pressed, mp_float_t interval, size_t max_events) {
  
      digitalio_digitalinout_obj_t *clock = m_new_obj(digitalio_digitalinout_obj_t);
      clock->base.type = &digitalio_digitalinout_type;
      common_hal_digitalio_digitalinout_construct(clock, clock_pin);
      common_hal_digitalio_digitalinout_switch_to_output(clock, false, DRIVE_MODE_PUSH_PULL);
      self->clock = clock;
  
      digitalio_digitalinout_obj_t *data = m_new_obj(digitalio_digitalinout_obj_t);
      data->base.type = &digitalio_digitalinout_type;
      common_hal_digitalio_digitalinout_construct(data, data_pin);
      common_hal_digitalio_digitalinout_switch_to_input(data, PULL_NONE);
      self->data = data;
  
      digitalio_digitalinout_obj_t *latch = m_new_obj(digitalio_digitalinout_obj_t);
      latch->base.type = &digitalio_digitalinout_type;
      common_hal_digitalio_digitalinout_construct(latch, latch_pin);
      common_hal_digitalio_digitalinout_switch_to_output(latch, true, DRIVE_MODE_PUSH_PULL);
      self->latch = latch;
      self->value_to_latch = value_to_latch;
  
      self->currently_pressed = (bool *)gc_alloc(sizeof(bool) * key_count, false, false);
      self->previously_pressed = (bool *)gc_alloc(sizeof(bool) * key_count, false, false);
      self->value_when_pressed = value_when_pressed;
      self->key_count = key_count;
  
      self->interval_ticks = (mp_uint_t)(interval * 1024);   // interval * 1000 * (1024/1000)
      self->last_scan_ticks = port_get_raw_ticks(NULL);
  
      keypad_eventqueue_obj_t *events = m_new_obj(keypad_eventqueue_obj_t);
      events->base.type = &keypad_eventqueue_type;
      common_hal_keypad_eventqueue_construct(events, max_events);
      self->events = events;
  
      // Add self to the list of active keypad scanners.
      keypad_register_scanner((keypad_scanner_obj_t *)self);
  }
  
  void common_hal_keypad_shiftregisterkeys_deinit(keypad_shiftregisterkeys_obj_t *self) {
      if (common_hal_keypad_shiftregisterkeys_deinited(self)) {
          return;
      }
  
      // Remove self from the list of active keypad scanners first.
      keypad_deregister_scanner((keypad_scanner_obj_t *)self);
  
  
      common_hal_digitalio_digitalinout_deinit(self->clock);
      self->clock = MP_ROM_NONE;
  
      common_hal_digitalio_digitalinout_deinit(self->data);
      self->data = MP_ROM_NONE;
  
      common_hal_digitalio_digitalinout_deinit(self->latch);
      self->latch = MP_ROM_NONE;
  }
  
  bool common_hal_keypad_shiftregisterkeys_deinited(keypad_shiftregisterkeys_obj_t *self) {
      return self->clock == MP_ROM_NONE;
  }
  
  size_t common_hal_keypad_shiftregisterkeys_get_key_count(keypad_shiftregisterkeys_obj_t *self) {
      return self->key_count;
  }
  
  mp_obj_t common_hal_keypad_shiftregisterkeys_get_events(keypad_shiftregisterkeys_obj_t *self) {
      return MP_OBJ_FROM_PTR(self->events);
  }
  
  void common_hal_keypad_shiftregisterkeys_reset(keypad_shiftregisterkeys_obj_t *self) {
      const size_t key_count = common_hal_keypad_shiftregisterkeys_get_key_count(self);
  
      supervisor_acquire_lock(&keypad_scanners_linked_list_lock);
      memset(self->previously_pressed, false, key_count);
      memset(self->currently_pressed, false, key_count);
      supervisor_release_lock(&keypad_scanners_linked_list_lock);
  }
  
  void keypad_shiftregisterkeys_scan(keypad_shiftregisterkeys_obj_t *self) {
      uint64_t now = port_get_raw_ticks(NULL);
      if (now - self->last_scan_ticks < self->interval_ticks) {
          // Too soon. Wait longer to debounce.
          return;
      }
  
      self->last_scan_ticks = now;
  
      mp_obj_t timestamp = supervisor_ticks_ms();
  
      // Latch (freeze) the current state of the input pins.
      common_hal_digitalio_digitalinout_set_value(self->latch, self->value_to_latch);
  
      const size_t key_count = common_hal_keypad_shiftregisterkeys_get_key_count(self);
  
      for (mp_uint_t key_number = 0; key_number < key_count; key_number++) {
          // Zero-th data appears on on the data pin immediately, without shifting.
          common_hal_digitalio_digitalinout_set_value(self->clock, false);
  
          // Remember the previous up/down state.
          const bool previous = self->currently_pressed[key_number];
          self->previously_pressed[key_number] = previous;
  
          // Get the current state.
          const bool current =
              common_hal_digitalio_digitalinout_get_value(self->data) == self->value_when_pressed;
          self->currently_pressed[key_number] = current;
  
          // Trigger a shift to get the next bit.
          common_hal_digitalio_digitalinout_set_value(self->clock, true);
  
          // Record any transitions.
          if (previous != current) {
              keypad_eventqueue_record(self->events, key_number, current, timestamp);
          }
      }
  
      // Start reading the input pins again.
      common_hal_digitalio_digitalinout_set_value(self->latch, !self->value_to_latch);
  }
  