M5Paper RTC set from NTP

m5paper_rtc_set_ntp.ino

#include <M5EPD.h>
#include <WiFi.h>

rtc_time_t RTCtime;
rtc_date_t RTCDate;

char timeStrbuff[64];

static const int JST = 3600 * 9;
static const char *wd[7] = {"Sun", "Mon", "Tue", "Wed", "Thr", "Fri", "Sat"};

RTC_SLOW_ATTR bool ntpDataFlag = false;

const char* ssid = "ssid";
const char* password = "password";
time_t t;
struct tm *tm;

void setupTime() {
  t = time(NULL);
  tm = localtime(&t);

  RTCtime.hour = tm->tm_hour;
  RTCtime.min = tm->tm_min;
  RTCtime.sec = tm->tm_sec;
  M5.RTC.setTime(&RTCtime);

  RTCDate.year = tm->tm_year + 1900;
  RTCDate.mon = tm->tm_mon + 1;
  RTCDate.day = tm->tm_mday;
  M5.RTC.setDate(&RTCDate);
}

void setup() {
  M5.begin();
  M5.RTC.begin();

  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    Serial.print('.');
    delay(500);
  }
  Serial.println();
  Serial.printf("Connected, IP address: ");
  Serial.println(WiFi.localIP());

  configTime( JST, 0, "ntp.nict.jp", "ntp.jst.mfeed.ad.jp");
  delay(2000);
  setupTime();
}

void loop() {
  // put your main code here, to run repeatedly:
  M5.RTC.getTime(&RTCtime);
  M5.RTC.getDate(&RTCDate);
  Serial.printf("%d/%02d/%02d (%s) %02d:%02d:%02d\n",
                RTCDate.year, RTCDate.mon, RTCDate.day,wd[RTCDate.week],
                RTCtime.hour, RTCtime.min, RTCtime.sec);
  delay(10000);
}