text: /*
   * Simple test using LWIP SNTP
   */
  
  /*-
   * Copyright (c) 2018, Jeff Kletsky
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions are met:
   *
   *     * Redistributions of source code must retain the above copyright
   *       notice, this list of conditions and the following disclaimer.
   *
   *     * Redistributions in binary form must reproduce the above copyright
   *       notice, this list of conditions and the following disclaimer in the
   *       documentation and/or other materials provided with the distribution.
   *
   *     * Neither the name of the copyright holder nor the
   *       names of its contributors may be used to endorse or promote products
   *       derived from this software without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
   * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
   * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  
  
  #include <esp8266.h>
  #include <esp/uart.h>
  
  #include <FreeRTOS.h>
  #include <task.h>
  
  /* espressif/esp_system.h uses "bool" but fails to #include */
  #include <stdbool.h>
  #include <espressif/esp_common.h>
  #include <espressif/esp_wifi.h>
  
  /*  For sdk_system_restart_in_nmi() */
  #include <esplibs/libmain.h>
  
  #include <stdio.h>
  #include <stdlib.h>
  
  #include <lwip/apps/sntp.h>
  
  
  #define BLUE_LED 2
  #define LED_ON 0
  #define LED_OFF 1
  
  #define WAIT_FOR_UART_SECS 5  /* 2 might be OK */
  
  #define TV2LD(TV) ((long double)TV.tv_sec + (long double)TV.tv_usec * 1.e-6)
  
  void
  sntp_task(void *pvParameters) {
  
      while (sdk_wifi_station_get_connect_status() != STATION_GOT_IP) {
          vTaskDelay(10);
      };
  
      /*
       * Set one of SNTP_OPMODE_LISTENONLY or SNTP_OPMODE_POLL
       */
  
  
      /*
       * SNTP_OPMODE_LISTENONLY
       *     just needs the mode set, no server names required
       *     (requires broadcast NTP on your network)
       */
  
      sntp_setoperatingmode(SNTP_OPMODE_LISTENONLY);
  
      /*
       * SNTP_OPMODE_POLL
       *     Needs one or more server names set
       *     additional servers are "fail over"
       *     Can use a DNS name or an address literal
       *     LWIP can also be configured with SNTP_GET_SERVERS_FROM_DHCP
       *     (DHCP-specified SNTP servers untested at this time)
       *
       *  NOTE: Early testing with polling shows higher deviations
       *        than seen with broadcast, even with RTT compensation
       *        Cause unknown at this time, but believed to be within SNTP
       *        amd not part of timekeeping itself.
       */
  
  /*
      sntp_setoperatingmode(SNTP_OPMODE_POLL);
      sntp_setservername(0, "ntp_a.example.com");
      sntp_setservername(1, "ntp_b.example.com");
      sntp_setservername(2, "ntp_c.example.com");
  */
  
      /* Once set up, this is all it takes */
      sntp_init();
  
      /*
       * Have high-priority thread "parked", might as well use it
       * Show calling gettimeofday() once an hour to check for timer wrap
       * (the SNTP process itself, if connected, should be sufficient)
       */
      while (1) {
          vTaskDelay(60 * 60 * (1000 / portTICK_PERIOD_MS));
          printf("gettimeofday(NULL, NULL)\n");
          gettimeofday(NULL, NULL);
      }
  }
  
  
  
  void
  user_init(void)
  {
      uart_set_baud(0, 115200);
      sdk_wifi_set_opmode(STATION_MODE);
      /*
       * Run at a high enough priority so that the initial time-set doesn't get interrupted
       * Later calls and listen-only mode calls run in the high-priority "tcpip_thread" (LWIP)
       *
       * While 196 heap seemed sufficient for many tests, use of an NTP pool
       * with DNS caused heap errors/warnings on starting NTP at 256 heap
       */
      xTaskCreate(sntp_task, "SNTP task", 288, NULL, 6, NULL);
  }
  