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PaperMono RTC Real-Time Clock
APIs and example programs for the PaperMono RTC.
Example Programs
Build Requirements
- M5Stack Board Manager version >= 3.3.9
- Board option =
M5PaperMono - M5Unified library version >= 0.2.20
- M5GFX library version >= 0.2.27
Setting the RTC Time Manually
cpp
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#include <M5Unified.h>
M5Canvas canvas(&M5.Display);
static constexpr const char* const wd[7] = {"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"};
static int last_drawn_minute = -1;
void drawScreen(const m5::rtc_datetime_t& dt)
{
const int w = M5.Display.width();
const int h = M5.Display.height();
char dateText[32];
char timeText[16];
snprintf(dateText, sizeof(dateText), "%04d/%02d/%02d", dt.date.year, dt.date.month, dt.date.date);
snprintf(timeText, sizeof(timeText), "%02d:%02d", dt.time.hours, dt.time.minutes);
canvas.fillSprite(TFT_WHITE);
canvas.setTextColor(TFT_BLACK);
canvas.setTextDatum(top_center);
canvas.setFont(&fonts::FreeSansBold18pt7b);
canvas.drawString("PaperMono RTC Test", w / 2, 24);
canvas.setFont(&fonts::FreeSansBold24pt7b);
canvas.setTextSize(1);
canvas.drawString(timeText, w / 2, h / 2 - 80);
canvas.setTextSize(1);
canvas.setFont(&fonts::FreeSansBold18pt7b);
canvas.drawString(dateText, w / 2, h / 2 + 48);
canvas.drawString(wd[dt.date.weekDay], w / 2, h / 2 + 94);
canvas.pushSprite(0, 0);
}
void drawErrorScreen(const char* message)
{
const int w = M5.Display.width();
const int h = M5.Display.height();
canvas.fillSprite(TFT_WHITE);
canvas.setTextDatum(middle_center);
canvas.setTextColor(TFT_BLACK);
canvas.setFont(&fonts::FreeSansBold18pt7b);
canvas.drawString("PaperMono RTC Test", w / 2, h / 2 - 48);
canvas.drawString(message, w / 2, h / 2 + 36);
canvas.pushSprite(0, 0);
}
void setup()
{
auto cfg = M5.config();
cfg.clear_display = false;
M5.begin(cfg);
M5.Display.setRotation(0);
M5.Display.setEpdMode(epd_mode_t::epd_text);
canvas.createSprite(M5.Display.width(), M5.Display.height());
if (!M5.Rtc.isEnabled()) {
drawErrorScreen("RTC not found");
while (true) {
delay(1000);
}
}
M5.Rtc.setDateTime({{2026, 8, 18}, {12, 0, 0}});
const auto dt = M5.Rtc.getDateTime();
drawScreen(dt);
last_drawn_minute = dt.time.minutes;
}
void loop()
{
M5.update();
const auto dt = M5.Rtc.getDateTime();
if (dt.time.minutes != last_drawn_minute) {
last_drawn_minute = dt.time.minutes;
drawScreen(dt);
}
delay(100);
}
SNTP Network Time
Note
Replace
ssid and password with your actual Wi-Fi network name and password before use.cpp
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#include <Arduino.h>
#include <M5GFX.h>
#include <M5Unified.h>
#include <WiFi.h>
#include <esp_sntp.h>
#include <sntp.h>
#define NTP_TIMEZONE "UTC-8"
#define NTP_SERVER1 "0.pool.ntp.org"
#define NTP_SERVER2 "1.pool.ntp.org"
#define NTP_SERVER3 "2.pool.ntp.org"
static constexpr uint32_t WIFI_CONNECT_TIMEOUT_MS = 20000;
static constexpr uint32_t SNTP_SYNC_TIMEOUT_MS = 30000;
M5Canvas canvas(&M5.Display);
const char* ssid = "ssid";
const char* password = "password";
static constexpr const char* const wd[7] = {"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"};
static int last_drawn_minute = -1;
void drawScreen(const m5::rtc_datetime_t& dt)
{
const int w = M5.Display.width();
const int h = M5.Display.height();
char dateText[32];
char timeText[16];
snprintf(dateText, sizeof(dateText), "%04d/%02d/%02d", dt.date.year, dt.date.month, dt.date.date);
snprintf(timeText, sizeof(timeText), "%02d:%02d", dt.time.hours, dt.time.minutes);
canvas.fillSprite(TFT_WHITE);
canvas.setTextColor(TFT_BLACK);
canvas.setTextDatum(top_center);
canvas.setFont(&fonts::FreeSansBold18pt7b);
canvas.drawString("PaperMono RTC Test", w / 2, 24);
canvas.drawString("SNTP", w / 2, 70);
canvas.setFont(&fonts::FreeSansBold24pt7b);
canvas.setTextSize(1);
canvas.drawString(timeText, w / 2, h / 2 - 80);
canvas.setFont(&fonts::FreeSansBold18pt7b);
canvas.drawString(dateText, w / 2, h / 2 + 48);
canvas.drawString(wd[dt.date.weekDay], w / 2, h / 2 + 94);
canvas.pushSprite(0, 0);
}
void drawSyncScreen()
{
const int w = M5.Display.width();
const int h = M5.Display.height();
canvas.fillSprite(TFT_WHITE);
canvas.setTextDatum(middle_center);
canvas.setTextColor(TFT_BLACK);
canvas.setFont(&fonts::FreeSansBold18pt7b);
canvas.drawString("PaperMono RTC Test", w / 2, h / 2 - 72);
canvas.drawString("SNTP Sync....", w / 2, h / 2);
canvas.setFont(&fonts::FreeSansBold12pt7b);
canvas.drawString("Please wait", w / 2, h / 2 + 52);
canvas.pushSprite(0, 0);
}
void drawErrorScreen(const char* message)
{
const int w = M5.Display.width();
const int h = M5.Display.height();
canvas.fillSprite(TFT_WHITE);
canvas.setTextDatum(middle_center);
canvas.setTextColor(TFT_BLACK);
canvas.setFont(&fonts::FreeSansBold18pt7b);
canvas.drawString("PaperMono RTC Test", w / 2, h / 2 - 48);
canvas.drawString(message, w / 2, h / 2 + 36);
canvas.pushSprite(0, 0);
}
bool connectWiFi()
{
WiFi.mode(WIFI_STA);
WiFi.begin(ssid, password);
const uint32_t start_ms = millis();
while (WiFi.status() != WL_CONNECTED) {
if (millis() - start_ms >= WIFI_CONNECT_TIMEOUT_MS) {
return false;
}
delay(250);
}
Serial.printf("WiFi connected, IP: %s\r\n", WiFi.localIP().toString().c_str());
return true;
}
bool syncRtcFromSntp()
{
Serial.println("SNTP sync start...");
configTzTime(NTP_TIMEZONE, NTP_SERVER1, NTP_SERVER2, NTP_SERVER3);
const uint32_t start_ms = millis();
while (sntp_get_sync_status() != SNTP_SYNC_STATUS_COMPLETED) {
if (millis() - start_ms >= SNTP_SYNC_TIMEOUT_MS) {
return false;
}
delay(500);
}
time_t now = time(nullptr) + 1;
while (now > time(nullptr)) {
delay(10);
}
auto local_tm = localtime(&now);
if (local_tm == nullptr) {
return false;
}
M5.Rtc.setDateTime(local_tm);
Serial.printf("RTC synced from SNTP: %04d/%02d/%02d %02d:%02d:%02d (%s)\r\n",
local_tm->tm_year + 1900,
local_tm->tm_mon + 1,
local_tm->tm_mday,
local_tm->tm_hour,
local_tm->tm_min,
local_tm->tm_sec,
NTP_TIMEZONE);
return true;
}
void setup()
{
auto cfg = M5.config();
cfg.clear_display = false;
M5.begin(cfg);
Serial.begin(115200);
M5.Display.setRotation(0);
M5.Display.setEpdMode(epd_mode_t::epd_text);
canvas.createSprite(M5.Display.width(), M5.Display.height());
drawSyncScreen();
if (!M5.Rtc.isEnabled()) {
Serial.println("RTC not found.");
drawErrorScreen("RTC not found");
while (true) {
delay(1000);
}
}
if (!connectWiFi()) {
Serial.println("WiFi connect failed.");
drawErrorScreen("WiFi failed");
while (true) {
delay(1000);
}
}
if (!syncRtcFromSntp()) {
Serial.println("SNTP sync failed.");
drawErrorScreen("SNTP failed");
while (true) {
delay(1000);
}
}
const auto dt = M5.Rtc.getDateTime();
drawScreen(dt);
last_drawn_minute = dt.time.minutes;
}
void loop()
{
M5.update();
const auto dt = M5.Rtc.getDateTime();
if (dt.time.minutes != last_drawn_minute) {
last_drawn_minute = dt.time.minutes;
drawScreen(dt);
}
delay(100);
}
API
The PaperMono RTC features use Rtc_Class from the M5Unified library. For more information, refer to the following documentation:
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