Real Time Clock Module, LCD Display and Controller Time

created by hek , updated

This example shows how you can fetch current time from the controller and put it to a battery backed up Real Time Clock (RTC) module attached to your Arduino.

If your sensor later loses connection with controller or power cycles it can pick up time from the local RTC. The module uses a CR2032 battery for time backup which should last for about 3-4 years.

We've also attached a LCD Display showing time and temperature [coming from the internal temperature sensor in the RTC module].

No sensor data is being sent to the controller in this example.

Wiring Things Up

Start by connecting the radio module.

RTC Module LCD Display Arduino
VCC VCC +5V
SDA SDA A4
SCL SCL A5

Example

This example uses the external TimeLib, DS3232RTC and LiquidCrystal_I2C libraries found here. Please install them and restart the Arduino IDE before trying to compile.

/mysensors/MySensorsArduinoExamples/examples/RealTimeClockDisplaySensor/RealTimeClockDisplaySensor.ino
Last updated by petewill, 14 Oct 2016, "Update sketches to use updated Time library"

/**
 * The MySensors Arduino library handles the wireless radio link and protocol
 * between your home built sensors/actuators and HA controller of choice.
 * The sensors forms a self healing radio network with optional repeaters. Each
 * repeater and gateway builds a routing tables in EEPROM which keeps track of the
 * network topology allowing messages to be routed to nodes.
 *
 * Created by Henrik Ekblad <[email protected]>
 * Copyright (C) 2013-2015 Sensnology AB
 * Full contributor list: https://github.com/mysensors/Arduino/graphs/contributors
 *
 * Documentation: http://www.mysensors.org
 * Support Forum: http://forum.mysensors.org
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * version 2 as published by the Free Software Foundation.
 *
 *******************************
 *
 * REVISION HISTORY
 * Version 1.0 - Henrik Ekblad
 * 
 * DESCRIPTION
 * Example sketch showing how to request time from controller which is stored in RTC module
 * The time and temperature (DS3231/DS3232) is shown on an attached Crystal LCD display
 * 
 *
 * Wiring (radio wiring on www.mysensors.org)
 * ------------------------------------
 * Arduino   RTC-Module     I2C Display 
 * ------------------------------------
 * GND       GND            GND
 * +5V       VCC            VCC
 * A4        SDA            SDA
 * A5        SCL            SCL
 *
 * http://www.mysensors.org/build/display
 *
 */

// Enable debug prints to serial monitor
#define MY_DEBUG 

// Enable and select radio type attached
#define MY_RADIO_NRF24
//#define MY_RADIO_RFM69

#include <SPI.h>
#include <MySensors.h>  
#include <TimeLib.h> 
#include <DS3232RTC.h>  // A  DS3231/DS3232 library
#include <Wire.h>
#include <LiquidCrystal_I2C.h>

bool timeReceived = false;
unsigned long lastUpdate=0, lastRequest=0;

// Initialize display. Google the correct settings for your display. 
// The follwoing setting should work for the recommended display in the MySensors "shop".
LiquidCrystal_I2C lcd(0x27, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE);

void setup()  
{  
  // the function to get the time from the RTC
  setSyncProvider(RTC.get);  

  // Request latest time from controller at startup
  requestTime();  

  // initialize the lcd for 16 chars 2 lines and turn on backlight
  lcd.begin(16,2); 
}

void presentation()  {
  // Send the sketch version information to the gateway and Controller
  sendSketchInfo("RTC Clock", "1.0");
}

// This is called when a new time value was received
void receiveTime(unsigned long controllerTime) {
  // Ok, set incoming time 
  Serial.print("Time value received: ");
  Serial.println(controllerTime);
  RTC.set(controllerTime); // this sets the RTC to the time from controller - which we do want periodically
  timeReceived = true;
}

void loop()     
{     
  unsigned long now = millis();

  // If no time has been received yet, request it every 10 second from controller
  // When time has been received, request update every hour
  if ((!timeReceived && (now-lastRequest) > (10UL*1000UL))
    || (timeReceived && (now-lastRequest) > (60UL*1000UL*60UL))) {
    // Request time from controller. 
    Serial.println("requesting time");
    requestTime();  
    lastRequest = now;
  }

  // Update display every second
  if (now-lastUpdate > 1000) {
    updateDisplay();  
    lastUpdate = now;
  }
}


void updateDisplay(){
  tmElements_t tm;
  RTC.read(tm);

  // Print date and time 
  lcd.home();
  lcd.print(tm.Day);
  lcd.print("/");
  lcd.print(tm.Month);
//  lcd.print(" ");
//  lcd.print(tmYearToCalendar(tm.Year)-2000);

  lcd.print(" ");
  printDigits(tm.Hour);
  lcd.print(":");
  printDigits(tm.Minute);
  lcd.print(":");
  printDigits(tm.Second);

  // Go to next line and print temperature
  lcd.setCursor ( 0, 1 );  
  lcd.print("Temp: ");
  lcd.print(RTC.temperature()/4);
  lcd.write(223); // Degree-sign
  lcd.print("C");
}


void printDigits(int digits){
  if(digits < 10)
    lcd.print('0');
  lcd.print(digits);
}

Datasheets

NameSize# Downloads
DS3231.pdf824.05 kB165

Shopping Guide

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Battery backed up clock module. DS3231 AT24C32 IIC.
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