text: /*
   * This file is part of the MicroPython project, http://micropython.org/
   *
   * The MIT License (MIT)
   *
   * Copyright (c) 2019 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 <stdlib.h>
  
  #include "py/obj.h"
  #include "py/runtime.h"
  #include "lib/timeutils/timeutils.h"
  #include "shared-bindings/rtc/__init__.h"
  #include "supervisor/port.h"
  #include "supervisor/shared/translate.h"
  
  // This is the time in seconds since 2000 that the RTC was started.
  __attribute__((section(".uninitialized"))) static uint32_t rtc_offset[3];
  
  // These values are placed before and after the current RTC count.  They are
  // used to determine if the RTC count is valid.  These randomly-generated values
  // will be set when the RTC value is set in order to mark the RTC as valid. If
  // the system crashes or reboots, these values will remain undisturbed and the
  // RTC offset will remain valid.
  //
  // If Circuit Python is updated or these symbols shift around, the prefix and
  // suffix will no longer match, and the time will no longer be valid.
  #define RTC_OFFSET_CHECK_PREFIX 0x25ea7e2a
  #define RTC_OFFSET_CHECK_SUFFIX 0x2b80b69e
  
  void common_hal_rtc_init(void) {
      // If the prefix and suffix are not valid, zero-initialize the RTC offset.
      if ((rtc_offset[0] != RTC_OFFSET_CHECK_PREFIX) || (rtc_offset[2] != RTC_OFFSET_CHECK_SUFFIX)) {
          rtc_offset[1] = 0;
      }
  }
  
  void common_hal_rtc_get_time(timeutils_struct_time_t *tm) {
      uint64_t ticks_s = port_get_raw_ticks(NULL) / 1024;
      timeutils_seconds_since_2000_to_struct_time(rtc_offset[1] + ticks_s, tm);
  }
  
  void common_hal_rtc_set_time(timeutils_struct_time_t *tm) {
      uint64_t ticks_s = port_get_raw_ticks(NULL) / 1024;
      uint32_t epoch_s = timeutils_seconds_since_2000(
          tm->tm_year, tm->tm_mon, tm->tm_mday, tm->tm_hour, tm->tm_min, tm->tm_sec
          );
      rtc_offset[1] = epoch_s - ticks_s;
  
      // Set the prefix and suffix in order to indicate the time is valid.  This
      // must be done after the offset is updated, in case there is a crash or
      // power failure.
      rtc_offset[0] = RTC_OFFSET_CHECK_PREFIX;
      rtc_offset[2] = RTC_OFFSET_CHECK_SUFFIX;
  }
  
  int common_hal_rtc_get_calibration(void) {
      return 0;
  }
  
  void common_hal_rtc_set_calibration(int calibration) {
      mp_raise_NotImplementedError(translate("RTC calibration is not supported on this board"));
  }
  