RTC1307 - Real Time Clock

Wire.beginTransmission(DS1307_I2C_ADDRESS);   // Open I2C line in write mode
  Wire.write((byte)0x00);                              // Set the register pointer to (0x00)
  Wire.endTransmission();                       // End Write Transmission 
 
  Wire.requestFrom(DS1307_I2C_ADDRESS, 7);      // Open the I2C line in send mode
 
  second     = bcdToDec(Wire.read() & 0x7f); // Read seven bytes of data
  minute     = bcdToDec(Wire.read());
  hour       = bcdToDec(Wire.read() & 0x3f);  
  dayOfWeek  = bcdToDec(Wire.read());
  dayOfMonth = bcdToDec(Wire.read());
  month      = bcdToDec(Wire.read());
  year       = bcdToDec(Wire.read());

Wire.beginTransmission(DS1307_I2C_ADDRESS);  
  Wire.send(0x08);                             // Set the register pointer to (0x08) to read first memory byte
  Wire.endTransmission();                      
 
  Wire.requestFrom(DS1307_I2C_ADDRESS, 1);     // In this case only read one byte
 
  temp_byte     = Wire.read();              // Read the desired byte

Wire.beginTransmission(DS1307_I2C_ADDRESS);  // Open I2C line in write mode
 
   Wire.write((byte)0x00);                           // Set the register pointer to (0x00)
   Wire.write(decToBcd(second));               // Write seven bytes
   Wire.write(decToBcd(minute));
   Wire.write(decToBcd(hour));      
   Wire.write(decToBcd(dayOfWeek));
   Wire.write(decToBcd(dayOfMonth));
   Wire.write(decToBcd(month));
   Wire.write(decToBcd(year));
   Wire.endTransmission();                    // End write mode

Wire.beginTransmission(DS1307_I2C_ADDRESS);  
  Wire.write(0xf3);                             // Set the register pointer to (0xf3) to write the 11th memory byte
  Wire.write(0xa6);                             // Write the desired byte value
  Wire.endTransmission();

/* RTC Control v1.00 
 * by <http://www.combustory.com> John Vaughters
 *
 * THIS CODE IS FREE FOR ANYTHING  - There is no Rocket Science here. No need to create some long GPL statement.
 *
 * Credit to:
 * Maurice Ribble - http://www.glacialwanderer.com/hobbyrobotics for RTC DS1307 code
 * BB Riley - Underhill Center, VT  <brianbr@wulfden.org> For simplification of the Day of Week and month
 *                                                        and updating to Arduino 1.0 
 * peep rada - from Arduino Forum - Found that only 32 registers per I2C connection was possible 
 * 
 * With this code you can set the date/time, retreive the date/time and use the extra memory of an RTC DS1307 chip.  
 * The program also sets all the extra memory space to 0xff.
 * Serial Communication method with the Arduino that utilizes a leading CHAR for each command described below. 
 *
 * Commands:
 * T(00-59)(00-59)(00-23)(1-7)(01-31)(01-12)(00-99) - T(sec)(min)(hour)(dayOfWeek)(dayOfMonth)(month)(year) -
 * T - Sets the date of the RTC DS1307 Chip. 
 * Example to set the time for 25-Jan-2012 @ 19:57:11 for the 4 day of the week, use this command - T1157194250112
 * Q(1-2) - (Q1) Memory initialization  (Q2) RTC - Memory Dump  
 * R - Read/display the time, day and date
 *
 * ---------------------------------------------------------
 * Notes:
 * Version 1.0
 *    Moving this code to Version 1.0 because this code has been updated to Arduino v1.0 and the features have
 *    been well tested and improved in a collaborative effort.
 *    - Fixed the issue of not being able to access all the registers - JWV
 *    - Added initialization for all non-time registers - JWV
 *    - Added Dump of all 64 registers - JWV
 *    - Some Date/Time reformatting and cleanup of display, added Day/Month texts - BBR
 *    - Made compatible with Arduino 1.0 - BBR
 *    - Added Rr command for reading date/time - BBR
 *    - Made commands case insensitive - BBR
 *    - Create #define varibles to support pre Arduino v1.0 - JWV
 * Version 0.01
 *    Inital code with basics of setting time and the first 37 registers and dumping the first 32 registers. 
 *    The code was based on Maurice Ribble's original code.
 * 
 */
 
#include "Wire.h"
#define DS1307_I2C_ADDRESS 0x68  // This is the I2C address
// Arduino version compatibility Pre-Compiler Directives
#if defined(ARDUINO) && ARDUINO >= 100   // Arduino v1.0 and newer
  #define I2C_WRITE Wire.write 
  #define I2C_READ Wire.read
#else                                   // Arduino Prior to v1.0 
  #define I2C_WRITE Wire.send 
  #define I2C_READ Wire.receive
#endif
// Global Variables
int command = 0;       // This is the command char, in ascii form, sent from the serial port     
int i;
long previousMillis = 0;        // will store last time Temp was updated
byte second, minute, hour, dayOfWeek, dayOfMonth, month, year;
byte test;
byte zero;
char  *Day[] = {"","Sun","Mon","Tue","Wed","Thu","Fri","Sat"};
char  *Mon[] = {"","Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec"};
 
// Convert normal decimal numbers to binary coded decimal
byte decToBcd(byte val)
{
  return ( (val/10*16) + (val%10) );
}
 
// Convert binary coded decimal to normal decimal numbers
byte bcdToDec(byte val)
{
  return ( (val/16*10) + (val%16) );
}
 
// 1) Sets the date and time on the ds1307
// 2) Starts the clock
// 3) Sets hour mode to 24 hour clock
// Assumes you're passing in valid numbers, Probably need to put in checks for valid numbers.
 
void setDateDs1307()                
{
 
   second = (byte) ((Serial.read() - 48) * 10 + (Serial.read() - 48)); // Use of (byte) type casting and ascii math to achieve result.  
   minute = (byte) ((Serial.read() - 48) *10 +  (Serial.read() - 48));
   hour  = (byte) ((Serial.read() - 48) *10 +  (Serial.read() - 48));
   dayOfWeek = (byte) (Serial.read() - 48);
   dayOfMonth = (byte) ((Serial.read() - 48) *10 +  (Serial.read() - 48));
   month = (byte) ((Serial.read() - 48) *10 +  (Serial.read() - 48));
   year= (byte) ((Serial.read() - 48) *10 +  (Serial.read() - 48));
   Wire.beginTransmission(DS1307_I2C_ADDRESS);
   I2C_WRITE(zero);
   I2C_WRITE(decToBcd(second) & 0x7f);    // 0 to bit 7 starts the clock
   I2C_WRITE(decToBcd(minute));
   I2C_WRITE(decToBcd(hour));      // If you want 12 hour am/pm you need to set
                                   // bit 6 (also need to change readDateDs1307)
   I2C_WRITE(decToBcd(dayOfWeek));
   I2C_WRITE(decToBcd(dayOfMonth));
   I2C_WRITE(decToBcd(month));
   I2C_WRITE(decToBcd(year));
   Wire.endTransmission();
}
 
// Gets the date and time from the ds1307 and prints result
void getDateDs1307()
{
  // Reset the register pointer
  Wire.beginTransmission(DS1307_I2C_ADDRESS);
  I2C_WRITE(zero);
  Wire.endTransmission();
 
  Wire.requestFrom(DS1307_I2C_ADDRESS, 7);
 
  // A few of these need masks because certain bits are control bits
  second     = bcdToDec(I2C_READ() & 0x7f);
  minute     = bcdToDec(I2C_READ());
  hour       = bcdToDec(I2C_READ() & 0x3f);  // Need to change this if 12 hour am/pm
  dayOfWeek  = bcdToDec(I2C_READ());
  dayOfMonth = bcdToDec(I2C_READ());
  month      = bcdToDec(I2C_READ());
  year       = bcdToDec(I2C_READ());
 
  if (hour < 10)
    Serial.print("0");
  Serial.print(hour, DEC);
  Serial.print(":");
  if (minute < 10)
    Serial.print("0");
  Serial.print(minute, DEC);
  Serial.print(":");
  if (second < 10)
    Serial.print("0");
  Serial.print(second, DEC);
  Serial.print("  ");
  Serial.print(Day[dayOfWeek]);
  Serial.print(", ");
  Serial.print(dayOfMonth, DEC);
  Serial.print(" ");
  Serial.print(Mon[month]);
  Serial.print(" 20");
  if (year < 10)
    Serial.print("0");
  Serial.println(year, DEC);
 
}
 
 
void setup() {
  Wire.begin();
  Serial.begin(57600); 
  zero=0x00;
}
 
void loop() {
     if (Serial.available()) {      // Look for char in serial que and process if found
      command = Serial.read();
      if (command == 84 || command == 116) {      //If command = "Tt" Set Date
       setDateDs1307();
       getDateDs1307();
       Serial.println(" ");
      }
      else if (command == 82 || command == 114) {      //If command = "Rr" Read Date ... BBR
       getDateDs1307();
       Serial.println(" ");
      }
      else if (command == 81 || command == 113) {      //If command = "Qq" RTC1307 Memory Functions
        delay(100);     
        if (Serial.available()) {
         command = Serial.read(); 
         if (command == 49) {        //If command = "1" RTC1307 Initialize Memory - All Data will be set to 
                                       // 255 (0xff).  Therefore 255 or 0 will be an invalid value.  
           Wire.beginTransmission(DS1307_I2C_ADDRESS);   // 255 will be the init value and 0 will be considered 
                                                          // an error that occurs when the RTC is in Battery mode.
           I2C_WRITE(0x08); // Set the register pointer to be just past the date/time registers.
           for (i = 1; i <= 24; i++) {
               I2C_WRITE(0Xff);
              delay(10);
           }   
           Wire.endTransmission();
           Wire.beginTransmission(DS1307_I2C_ADDRESS);   
           I2C_WRITE(0x21); // Set the register pointer to 33 for second half of registers. Only 32 writes per connection allowed.
           for (i = 1; i <= 33; i++) {
               I2C_WRITE(0Xff);
              delay(10);
           }   
           Wire.endTransmission();
           getDateDs1307();
           Serial.println(": RTC1307 Initialized Memory");
         }
         else if (command == 50) {      //If command = "2" RTC1307 Memory Dump
          getDateDs1307();
          Serial.println(": RTC 1307 Dump Begin");
          Wire.beginTransmission(DS1307_I2C_ADDRESS);
          I2C_WRITE(zero);
          Wire.endTransmission();
          Wire.requestFrom(DS1307_I2C_ADDRESS, 32);
          for (i = 0; i <= 31; i++) {  //Register 0-31 - only 32 registers allowed per I2C connection
             test = I2C_READ();
             Serial.print(i);
             Serial.print(": ");
             Serial.print(test, DEC);
             Serial.print(" : ");
             Serial.println(test, HEX);
          }
          Wire.beginTransmission(DS1307_I2C_ADDRESS);
          I2C_WRITE(0x20);
          Wire.endTransmission();
          Wire.requestFrom(DS1307_I2C_ADDRESS, 32);  
          for (i = 32; i <= 63; i++) {         //Register 32-63 - only 32 registers allowed per I2C connection
             test = I2C_READ();
             Serial.print(i);
             Serial.print(": ");
             Serial.print(test, DEC);
             Serial.print(" : ");
             Serial.println(test, HEX);
          }
          Serial.println(" RTC1307 Dump end");
         } 
        }  
       }
      Serial.print("Command: ");
      Serial.println(command);     // Echo command CHAR in ascii that was sent
      }
      command = 0;                 // reset command 
      delay(100);
    }
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