M5Stack Core2: NTP で時刻を合わせる

こちらのプログラムを参考にしました。
Study:M5Stack Core2 / RTC & touch

プログラム

ntp_adjust/ntp_adjust.ino

// ---------------------------------------------------------------
/*
	ntp_adjust.ino

					Sep/02/2021

*/
// ---------------------------------------------------------------
#include <M5Core2.h>
#include <time.h>
#include <WiFiMulti.h>

// for WiFi
char ssid[] = "some-ssid";
char password[] = "some-password";
WiFiMulti wifiMulti;

// for Time
const char* ntpServer = "ntp.jst.mfeed.ad.jp";
const long  gmtOffset_sec = 9 * 3600;
const int   daylightOffset_sec = 0;
RTC_DateTypeDef RTC_DateStruct; // Data
RTC_TimeTypeDef RTC_TimeStruct; // Time
static const char *wd[7] = {"Sun","Mon","Tue","Wed","Thr","Fri","Sat"};
struct tm timeinfo;
String dateStr;
String timeStr;

// ---------------------------------------------------------------
void getTimeFromNTP()
{
	// To get Time from NTP server
	configTime(gmtOffset_sec, daylightOffset_sec, ntpServer);
	while (!getLocalTime(&timeinfo))
		{
		delay(1000);
		}
}

// ---------------------------------------------------------------
void setNTP2RTC()
{
	// timeSet
	getTimeFromNTP();
	getLocalTime(&timeinfo);
	// read RTC
	M5.Rtc.GetTime(&RTC_TimeStruct);
	M5.Rtc.GetDate(&RTC_DateStruct);
	// --- to over write date&time
	RTC_DateStruct.Year = timeinfo.tm_year + 1900;
	RTC_DateStruct.Month = timeinfo.tm_mon + 1;
	RTC_DateStruct.Date = timeinfo.tm_mday;
	RTC_DateStruct.WeekDay = timeinfo.tm_wday;
	M5.Rtc.SetDate(&RTC_DateStruct);
	RTC_TimeStruct.Hours = timeinfo.tm_hour;
	RTC_TimeStruct.Minutes = timeinfo.tm_min;
	RTC_TimeStruct.Seconds = timeinfo.tm_sec;
	M5.Rtc.SetTime(&RTC_TimeStruct);
}

// ---------------------------------------------------------------
void setup()
{
	M5.begin();
	M5.Lcd.fillScreen(BLACK);
	M5.Lcd.setTextColor(WHITE,BLACK);

	wifiMulti.addAP(ssid, password);

	Serial.println("*** setup *** end ***");
}

// ---------------------------------------------------------------
void loop()
{
	M5.Rtc.GetDate(&RTC_DateStruct);
	M5.Rtc.GetTime(&RTC_TimeStruct);
  M5.Lcd.setTextSize(3);
	M5.Lcd.setCursor(10, 60, 1);
	M5.Lcd.printf("%04d.%02d.%02d %s\n", RTC_DateStruct.Year, RTC_DateStruct.Month, RTC_DateStruct.Date, wd[RTC_DateStruct.WeekDay]);
 M5.Lcd.setTextSize(5);
	M5.Lcd.setCursor(30, 140, 1);
	M5.Lcd.printf("%02d:%02d:%02d", RTC_TimeStruct.Hours, RTC_TimeStruct.Minutes, RTC_TimeStruct.Seconds);

	delay(500);
}

// ---------------------------------------------------------------

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