RTC

Arduino RTC DS1307 Shield

NOTE: OBSOLETE! See:
https://arduinoinfo.mywikis.net/wiki/DS1307_RealTime_Clock_Brick

DS1307 is a real-time chip by the DALLAS company,which adopted the I2C protocol. It works well with Arduino, therefore is very convenient.

We designed the real clock module to pin out the I2C interface of Ds1307 but programmable Square Wave waveform output interface is also available.

Note, this module must be installed with the battery to work normally and retain data and time with power off.. The battery is a button (type CR1220), the positive upward:

Note : this module does not include the battery, due to new shipping regulations.

This module communicates with Arduino through the I2C interface. It is easiest with a 4-wire cable that plugs into the Sensor Shield communications connector. (see photo right)


But you can wire it directly yourself if needed. On most Arduino boards, SDA (data line) is on analog input pin 4, and SCL (clock line) is on analog input pin 5. On the Arduino Mega, SDA is digital pin 20 and SCL is 21. You also need Vcc (+5V) and GND.

Needed Library and Example Sketch:

Download the DS1307 Library 1 or Library 2

then uncompress DS1307 zip file into "libraries" folder of Arduino and restart ;

NOTE: A newer library with added functions like setting the square wave output frequency is HERE: and is highly recommended.
See "About Libraries" HERE:

Test Code (uses the newer Library only) :

Copy and paste into a blank Arduino IDE window.

/*
  RealTimeClockDS1307 - library to control a DS1307 RTC module
  Copyright (c) 2011 David H. Brown. All rights reserved
  
  Much thanks to John Waters and Maurice Ribble for their
  earlier and very helpful work (even if I didn't wind up
  using any of their code):
   - http://combustory.com/wiki/index.php/RTC1307_-_Real_Time_Clock
   - http://www.glacialwanderer.com/hobbyrobotics/?p=12

  This library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public
  License as published by the Free Software Foundation; either
  version 2.1 of the License, or (at your option) any later version.

  This library is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public
  License along with this library; if not, write to the Free Software
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/


#include <Wire.h>
#include <RealTimeClockDS1307.h>

//RealTimeClock RTC;//=new RealTimeClock();

#define Display_Clock_Every_N_Seconds 1
#define Display_ShortHelp_Every_N_Seconds 25
//#define TEST_Squarewave
//#define TEST_StopStart
//#define TEST_1224Switch

int count=0;
char formatted[] = "00-00-00 00:00:00x";

void setup() {
//  Wire.begin();
  Serial.begin(9600);
}

void loop() {
  if(Serial.available())
  {
    processCommand();
  }
  delay(1000);
  RTC.readClock();
  count++;
  if(count % Display_Clock_Every_N_Seconds == 0){
    Serial.print(count);
    Serial.print(": ");
    RTC.getFormatted(formatted);
    Serial.print(formatted);
    Serial.println();
  }

  if(count % Display_ShortHelp_Every_N_Seconds == 0) {
    Serial.println("Send ? for a list of commands.");
  }
#ifdef TEST_Squarewave
if(count%10 == 0)
{
  switch(count/10 % 6)
  {
    case 0:
    Serial.print("Squarewave disabled (low impedance): ");
    RTC.sqwDisable(0);
    Serial.println((int) RTC.readData(7));
    break;
    case 1:
    Serial.print("Squarewave disabled (high impedance): ");
    RTC.sqwDisable(1);
    Serial.println((int) RTC.readData(7));
    break;
    case 2:
    Serial.println("Squarewave enabled at 1 Hz");
    RTC.sqwEnable(RTC.SQW_1Hz);
    break;
    case 3:
    Serial.println("Squarewave enabled at 4.096 kHz");
    RTC.sqwEnable(RTC.SQW_4kHz);
    break;
    case 4:
    Serial.println("Squarewave enabled at 8.192 kHz");
    RTC.sqwEnable(RTC.SQW_8kHz);
    break;
    case 5:
    Serial.println("Squarewave enabled at 32.768 kHz");
    RTC.sqwEnable(RTC.SQW_32kHz);
    break;
    default:
    Serial.println("Squarewave test not defined");
  }//switch
}
#endif

#ifdef TEST_StopStart
if(count%10 == 0)
{
  if(!RTC.isStopped())
  {
    if(RTC.getSeconds() < 45)
    {
      Serial.println("Stopping clock for 10 seconds");
      RTC.stop();
    }//if we have enough time
  } else {
    RTC.setSeconds(RTC.getSeconds()+11);
    RTC.start();
    Serial.println("Adding 11 seconds and restarting clock");
  }
}//if on a multiple of 10 counts
#endif

#ifdef TEST_1224Switch
  if(count%10 == 0)
  {
    if(count %20 == 0)
    {
      Serial.println("switching to 12-hour time");
      RTC.switchTo12h();
      RTC.setClock();
    }
    else
    {
      Serial.println("switching to 24-hour time");
      RTC.switchTo24h();
      RTC.setClock();
    }
  }
#endif
}

void processCommand() {
  if(!Serial.available()) { return; }
  char command = Serial.read();
  int in,in2;
  switch(command)
  {
    case 'H':
    case 'h':
    in=SerialReadPosInt();
    RTC.setHours(in);
    RTC.setClock();
    Serial.print("Setting hours to ");
    Serial.println(in);
    break;
    case 'I':
    case 'i':
    in=SerialReadPosInt();
    RTC.setMinutes(in);
    RTC.setClock();
    Serial.print("Setting minutes to ");
    Serial.println(in);
    break;
    case 'S':
    case 's':
    in=SerialReadPosInt();
    RTC.setSeconds(in);
    RTC.setClock();
    Serial.print("Setting seconds to ");
    Serial.println(in);
    break;
    case 'Y':
    case 'y':
    in=SerialReadPosInt();
    RTC.setYear(in);
    RTC.setClock();
    Serial.print("Setting year to ");
    Serial.println(in);
    break;
    case 'M':
    case 'm':
    in=SerialReadPosInt();
    RTC.setMonth(in);
    RTC.setClock();
    Serial.print("Setting month to ");
    Serial.println(in);
    break;
    case 'D':
    case 'd':
    in=SerialReadPosInt();
    RTC.setDate(in);
    RTC.setClock();
    Serial.print("Setting date to ");
    Serial.println(in);
    break;
    case 'W':
    Serial.print("Day of week is ");
    Serial.println((int) RTC.getDayOfWeek());
    break;
    case 'w':
    in=SerialReadPosInt();
    RTC.setDayOfWeek(in);
    RTC.setClock();
    Serial.print("Setting day of week to ");
    Serial.println(in);
    break;

    case 't':
    case 'T':
    if(RTC.is12hour()) {
      RTC.switchTo24h();
      Serial.println("Switching to 24-hour clock.");
    } else {
      RTC.switchTo12h();
      Serial.println("Switching to 12-hour clock.");
    }
    RTC.setClock();
    break;

    case 'A':
    case 'a':
    if(RTC.is12hour()) {
      RTC.setAM();
      RTC.setClock();
      Serial.println("Set AM.");
    } else {
      Serial.println("(Set hours only in 24-hour mode.)");
    }
    break;

    case 'P':
    case 'p':
    if(RTC.is12hour()) {
      RTC.setPM();
      RTC.setClock();
      Serial.println("Set PM.");
    } else {
      Serial.println("(Set hours only in 24-hour mode.)");
    }
    break;

    case 'q':
    RTC.sqwEnable(RTC.SQW_1Hz);
    Serial.println("Square wave output set to 1Hz");
    break;
    case 'Q':
    RTC.sqwDisable(0);
    Serial.println("Square wave output disabled (low)");
    break;

    case 'z':
    RTC.start();
    Serial.println("Clock oscillator started.");
    break;
    case 'Z':
    RTC.stop();
    Serial.println("Clock oscillator stopped.");
    break;

    case '>':
    in=SerialReadPosInt();
    in2=SerialReadPosInt();
    RTC.writeData(in, in2);
    Serial.print("Write to register ");
    Serial.print(in);
    Serial.print(" the value ");
    Serial.println(in2);
    break;
    case '<':
    in=SerialReadPosInt();
    in2=RTC.readData(in);
    Serial.print("Read from register ");
    Serial.print(in);
    Serial.print(" the value ");
    Serial.println(in2);
    break;

    default:
    Serial.println("Unknown command. Try these:");
    Serial.println(" h## - set Hours       d## - set Date");
    Serial.println(" i## - set mInutes     m## - set Month");
    Serial.println(" s## - set Seconds     y## - set Year");
    Serial.println(" w## - set arbitrary day of Week");
    Serial.println(" t   - toggle 24-hour mode");
    Serial.println(" a   - set AM          p   - set PM");
    Serial.println();
    Serial.println(" z   - start clock     Z   - stop clock");
    Serial.println(" q   - SQW/OUT = 1Hz   Q   - stop SQW/OUT");
    Serial.println();
    Serial.println(" >##,###  - write to register ## the value ###");
    Serial.println(" <##      - read the value in register ##");

  }//switch on command

}

//read in numeric characters until something else
//or no more data is available on serial.
int SerialReadPosInt() {
  int i = 0;
  boolean done=false;
  while(Serial.available() && !done)
  {
    char c = Serial.read();
    if (c >= '0' && c <='9')
    {
      i = i * 10 + (c-'0');
    }
    else
    {
      done = true;
    }
  }
  return i;
}