wiring_pulse.c

/*
  pulse.c - wiring pulseIn implementation for esp8266
  Copyright (c) 2015 Hristo Gochkov. All rights reserved.
  This file is part of the esp8266 core for Arduino environment.
  This library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public
  License as published by the Free Software Foundation; either
  version 2.1 of the License, or (at your option) any later version.
  This library is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  Lesser General Public License for more details.
  You should have received a copy of the GNU Lesser General Public
  License along with this library; if not, write to the Free Software
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/
//#include <limits.h>
#include "wiring_private.h"
#include "pins_arduino.h"
#include "esp_cpu.h"

#define WAIT_FOR_PIN_STATE(state)                                         \
  while (digitalRead(pin) != (state)) {                                   \
    if (esp_cpu_get_cycle_count() - start_cycle_count > timeout_cycles) { \
      return 0;                                                           \
    }                                                                     \
  }

// max timeout is 27 seconds at 160MHz clock and 54 seconds at 80MHz clock
unsigned long pulseIn(uint8_t pin, uint8_t state, unsigned long timeout) {
  const uint32_t max_timeout_us = clockCyclesToMicroseconds(UINT_MAX);
  if (timeout > max_timeout_us) {
    timeout = max_timeout_us;
  }
  const uint32_t timeout_cycles = microsecondsToClockCycles(timeout);
  const uint32_t start_cycle_count = esp_cpu_get_cycle_count();
  WAIT_FOR_PIN_STATE(!state);
  WAIT_FOR_PIN_STATE(state);
  const uint32_t pulse_start_cycle_count = esp_cpu_get_cycle_count();
  WAIT_FOR_PIN_STATE(!state);
  return clockCyclesToMicroseconds(esp_cpu_get_cycle_count() - pulse_start_cycle_count);
}

unsigned long pulseInLong(uint8_t pin, uint8_t state, unsigned long timeout) {
  return pulseIn(pin, state, timeout);
}