/*                                  WWVB Translator
                                    A C Backus 8/18

To provide a digital signal to key a low power 60 kHz transmitter
to simulate the WWVB time code signal, taking the time and date from the GPS system.
Code is for Adafruit GPS modules using MTK3329/MTK3339 driver.
*/

#include <Adafruit_GPS.h>              // must have downloaded this library
#include <SoftwareSerial.h>

//   Connect the GPS TX pad to Digital 8
//   Connect the GPS RX pad to Digital 7

SoftwareSerial mySerial(8, 7);         // start soft serial and set pins for I/O

// set data rates:
#define PMTK_SET_NMEA_UPDATE_01HZ "$PMTK220,10000*2F"  // 0.1 Hz, 10 sec wait
#define PMTK_SET_NMEA_UPDATE_02HZ "$PMTK220,5000*1B"   // 0.2 Hz, 5 sec wait
#define PMTK_SET_NMEA_UPDATE_1HZ  "$PMTK220,1000*1F"
#define PMTK_SET_NMEA_UPDATE_5HZ  "$PMTK220,200*2C"
#define PMTK_SET_NMEA_UPDATE_10HZ "$PMTK220,100*2F"

// set baud rates for GPS:
#define PMTK_SET_NMEA_BAUDRATE_38400 "PMTK251,38400*27"
#define PMTK_SET_NMEA_BAUDRATE_9600 "$PMTK251,9600*17"
#define PMTK_SET_NMEA_BAUDRATE_4800 "PMTK251,4800*14"

// turn on only RMC sentence:
#define PMTK_SET_NMEA_OUTPUT_RMCONLY "$PMTK314,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0*29"
// turn on RMC and GGA sentences:
#define PMTK_SET_NMEA_OUTPUT_RMCGGA "$PMTK314,0,1,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0*28"
// turn on ALL THE DATA:
#define PMTK_SET_NMEA_OUTPUT_ALLDATA "$PMTK314,1,1,1,1,1,1,0,0,0,0,0,0,0,0,0,0,0,0,0*28"
// turn off output:
#define PMTK_SET_NMEA_OUTPUT_OFF "$PMTK314,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0*28"
// get hardware version:
#define PMTK_Q_RELEASE "$PMTK605*31"
// turn off the default antenna report:
#define PGCMD_SET_NMEA_ANTRPTOFF "$PGCMD,33,0*6D"

char c = 'A';                    // dummy character variable
int n = 0;                       // dummy counting variable
int x = 0;                       // dummy counting variable
unsigned long timestamp = 0;     // time stamp for data
char sentence[75];               // data sentence

int dst = 0;                     // 1 for DST; 0 for standard
int dstwarn = 0;                 // changes one day before DST change
int dayDSTon = 0;                // day number(of the year) when DST goes on
int dayDSToff = 0;               // day number(of the year) when DST goes off

int year = 0;                    // two-digit year, beginning 2000
int month = 0;                   // 1-12
int dayyear = 0;                 // day number within the year
int daytemp = 0;                 // temp storage of day number
int daymonth = 0;                // day number within the month
int hour = 0;                    // 0-23
int minute = 0;                  // 0-59
int second = 0;                  // 0-59
int msecond = 0;                 // milliseconds

void setup()
{  
  pinMode(2,OUTPUT);             // HIGH turns on 60 kHz carrier
  digitalWrite(2, HIGH);         // default for signal is ON
  
  Serial.begin(115200);          // start serial connection over USB
  mySerial.begin(9600);          // start soft serial connection at default GPS rate

  mySerial.println(PMTK_SET_NMEA_BAUDRATE_9600);    // set GPS baud rate to 9600
  mySerial.println(PMTK_SET_NMEA_UPDATE_10HZ);      // set data rate at 10 Hz
  mySerial.println(PGCMD_SET_NMEA_ANTRPTOFF);       // turn off antenna report
  mySerial.println(PMTK_SET_NMEA_OUTPUT_RMCONLY);   // turn output on only for RMC
  
  delay(2000);                   // wait for GPS to send ack sentences
}

void loop()
{
  getdata();                     // get 74 data characters starting after '$' (final is a null)
  getdata();                     // do again to be sure everything was synced up
  while(int(sentence[10])==53 || timestamp > 4294907296)
  {                              // check if sentence too close to the end of the minute (at 50+ sec)
    getdata();                   // or the millis() max bits rollover (within 60 seconds)
  }                              // if either, get another sentence
  parsedata();                   // read charater data into variables
  dayyearcalc();                 // calculate day number of the year from date and month
  minuteincrement();             // set variables for the next minute
  dstset();                      // calculate and set DST flags
  
// calulate delay before starting transmit on the next minute (with final correction):
  delay(60000 - (1000*second + msecond) - (millis() - timestamp) - 300);

  Serial.print("Year: ");
  Serial.println(year);
  Serial.print("Day: ");
  Serial.println(dayyear);
  Serial.print("Hour: ");
  Serial.println(hour);
  Serial.print("Minute: ");
  Serial.println(minute);
  Serial.println();
  
// run five minutes before refreshing data:
  for(n=0;n>=5;n++)
  {
    transmit();
    minuteincrement();
  }
}

// getdata() reads the serial output from the GPS, first clearing out the receive buffer,
// then looking for a '$', which marks the beginnning of the RMC sentence -- then
// reading the next 74 characters into the sentence[75] character array:
void getdata()
{
  while(mySerial.available())      // clear out receive buffer
  {
    c = mySerial.read();
  }
  
  c = 'x';
  
  while(c != '$')                  // look for '$'
  {
    if(mySerial.available())
    {
      c = mySerial.read();
      timestamp = millis();        // time stamp the sentence
    }
  }
  
  n = 0;
  
  while(n < 74)                    // collect the next 74 characters
  {
    if(mySerial.available())
    {
      sentence[n] = mySerial.read();
      n = n + 1;
    }
  }
}

// parsedata() reads the character data from the sentence[75] character array and
// populates the appropriate variables with corresponding integer data, converting
// from ASCII character numbers for the digits to the digits themselves by
// subtracting 48, the ASCII decimal code for zero:
void parsedata()
{
// the time data appear first in the RMC sentence, six characters beyond the start:
  hour = 10*(int(sentence[6])-48) + int(sentence[7])-48;
  minute = 10*(int(sentence[8])-48) + int(sentence[9])-48;
  second = 10*(int(sentence[10])-48) + int(sentence[11])-48;
  msecond = 100*(int(sentence[13])-48) + 10*(int(sentence[14])-48) + int(sentence[15])-48;

// the date data appear near the end, just before the * signifying that the error
// correction bytes follow -- whether or not there is a GPS fix:
  for (n=15;sentence[n]!='*';n++)  // find '*', looking beyond the time data
  {
    x = n - 9;
  }
  daymonth = 10*(int(sentence[x])-48) + int(sentence[x+1])-48;
  month = 10*(int(sentence[x+2])-48) + int(sentence[x+3])-48;
  year = 10*(int(sentence[x+4])-48) + int(sentence[x+5]-48);
}

void dayyearcalc()                 // determine the dayyear from the month and daymonth
{
  x = 0;
  if(year%4 == 0)                  // set x to 1 if leap year
  {
    x = 1;
  }
  if(month == 1)
  {
    dayyear = daymonth;
  }
  if(month == 2)
  {
    dayyear = daymonth + 31;
  }
  if(month == 3)
  {
      dayyear = daymonth + 59 + x;
  }
  if(month == 4)
  {
      dayyear = daymonth + 90 + x;
  }
  if(month == 5)
  {
      dayyear = daymonth + 120 + x;
  }
  if(month == 6)
  {
      dayyear = daymonth + 151 + x;
  }
  if(month == 7)
  {
      dayyear = daymonth + 181 + x;
  }
  if(month == 8)
  {
      dayyear = daymonth + 212 + x;
  }
  if(month == 9)
  {
      dayyear = daymonth + 243 + x;
  }
  if(month == 10)
  {
      dayyear = daymonth + 273 + x;
  }
  if(month == 11)
  {
      dayyear = daymonth + 304 + x;
  }
  if(month == 12)
  {
      dayyear = daymonth + 334 + x;
  }
}

// dstset() determines the dayyear for the start and end of DST then sets or unsets
// the flags for the 57th and 58th seconds in the WWVB time code:
void dstset()
{
  daytemp = dayyear;          // store current dayyear

  month = 3;                  // determine dayyear of 2nd Sunday in March
  daymonth = 1;
  dayyearcalc();
  while((5 + dayyear + year*365 + (year+3)/4)%7 != 0)  // Sunday == 0; find the first
  {
    dayyear++;
  }
  dayDSTon = dayyear + 7;     // set DST-on variable to second Sunday

  month = 11;                 // determine dayyear of 1st Sunday in November
  daymonth = 1;
  dayyearcalc();
  while((5 + dayyear + year*365 + (year+3)/4)%7 != 0)  // a Sunday == 0; find the first
  {
    dayyear++;
  }
  dayDSToff = dayyear;        // set DST-off variable to 1st Sunday in November
  
  dayyear = daytemp;          // return dayyear to current value

  dstwarn = 0;                // set warn flag to zero for beginning of the year
  dst = 0;                    // set change flag to zero for the beginning of the year

  if(dayyear >= (dayDSTon - 1))     // set warning flag if it is the day before change or later
  {
    dstwarn = 1;
  }
  if(dayyear >= dayDSTon)           // set change flag if it is the change day or later
  {
    dst = 1;
  }
  if(dayyear >= (dayDSToff - 1))    // unset warning flag if it is the day before change or later
  {
    dstwarn = 0;
  }
  if(dayyear >= dayDSToff)          // unset change flag if it is the change day or later
  {
    dst = 0;
  }
}

// minuteincrement() increases the minute variable by one and then makes the
// subsequent resulting changes in other time variables:
void minuteincrement()
{
  minute = minute + 1;

  if(minute == 60)
  {
    minute = 0;
    hour++;
    if(hour == 24)
    {
      hour = 0;
      dayyear++;
      if(year%4 == 0)
      {
        if(dayyear == 367)
        {
          year++;
        }
      }
      else
      {
        if(dayyear == 366)
        {
        year++;
        }
      }
    }
  }
}

// transmit() determines from the time and date variables the appropriate BCD code elements
// to be sent at each second of the minute of code transmission; in addition to zeros and ones,
// there is a mark element sent every ten seconds:
void transmit()
{
  mark();              //second 00 -- marks the beginning of the minute

  x = minute;          //second 01 -- beginning of MINUTE code
  if(x/40 == 1)
  {
    one();
    x = x-40;
  }
  else
  {
    zero();
  }

  if(x/20 == 1)        //second 02
  {
    one();
    x = x-20;
  }
  else
  {
    zero();
  }

  if(x/10 == 1)        //second 03
  {
    one();
    x = x-10;
  }
  else
  {
    zero();
  }

  zero();              //second 04
  
  if(x/8 == 1)         //second 05
  {
    one();
    x = x-8;
  }
  else
  {
    zero();
  }

  if(x/4 == 1)         //second 06
  {
    one();
    x = x-4;
  }
  else
  {
    zero();
  }

  if(x/2 == 1)         //second 07
  {
    one();
    x = x-2;
  }
  else
  {
    zero();
  }

  if(x/1 == 1)         //second 08
  {
    one();
    x = x-1;
  }
  else
  {
    zero();
  }

  mark();              //second 09

  zero();              //second 10
  
  zero();              //second 11
  
  x = hour;            //second 12 -- beginning of HOUR code
  if(x/20 == 1)
  {
    one();
    x = x-20;
  }
  else
  {
    zero();
  }

  if(x/10 == 1)        //second 13
  {
    one();
    x = x-10;
  }
  else
  {
    zero();
  }

  zero();              //second 14

  if(x/8 == 1)         //second 15
  {
    one();
    x = x-8;
  }
  else
  {
    zero();
  }

  if(x/4 == 1)         //second 16
  {
    one();
    x = x-4;
  }
  else
  {
    zero();
  }

  if(x/2 == 1)         //second 17
  { 
    one();
    x = x-2;
  }
  else
  {
    zero();
  }

  if(x/1 == 1)         //second 18
  {
    one();
    x = x-1;
  }
  else
  {
    zero();
  }

  mark();              //second 19

  zero();              //second 20

  zero();              //second 21

  x = dayyear;         //second 22 -- beginning of DAY code
  if(x/200 == 1)
  {
    one();
    x = x-200;
  }
  else
  {
    zero();
  }

  if(x/100 == 1)       //second 23
  {
    one();
    x = x-100;
  }
  else
  {
    zero();
  }

  zero();              //second 24

  if(x/80 == 1)        //second 25
  {
    one();
    x = x-80;
  }
  else
  {
    zero();
  }

  if(x/40 == 1)        //second 26
  {
    one();
    x = x-40;
  }
  else
  {
    zero();
  }

  if(x/20 == 1)        //second 27
  {
    one();
    x = x-20;
  }
  else
  {
    zero();
  }

  if(x/10 == 1)        //second 28
  {
    one();
    x = x-10;
  }
  else
  {
    zero();
  }

  mark();              //second 29

  if(x/8 == 1)         //second 30
  {
    one();
    x = x-8;
  }
  else
  {
    zero();
  }

  if(x/4 == 1)         //second 31
  {
    one();
    x = x-4;
  }
  else
  {
    zero();
  }

  if(x/2 == 1)         //second 32
  {
    one();
    x = x-2;
  }
  else
  {
    zero();
  }

  if(x/1 == 1)         //second 33
  {
    one();
    x = x-1;
  }
  else
  {
    zero();
  }

  zero();              //second 34

  zero();              //second 35

  one();               //second 36 -- UT1 correction positive

  zero();              //second 37 -- UT1 correction positive 

  one();               //second 38 -- UT1 correction positive

  mark();              //second 39
  
  zero();              //second 40 -- zero UT1 correction
  
  zero();              //second 41 -- zero UT1 correction
  
  zero();              //second 42 -- zero UT1 correction
  
  zero();              //second 43 -- zero UT1 correction
  
  zero();              //second 44

  x = year;            //second 45 -- beginning of YEAR code
  if(x/80 == 1)
  {
    one();
    x = x-80;
  }
  else
  {
    zero();
  }

  if(x/40 == 1)        //second 46
  {
    one();
    x = x-40;
  }
  else
  {
    zero();
  }

  if(x/20 == 1)        //second 47
  {
    one();
    x = x-20;
  }
  else
  {
    zero();
  }

  if(x/10 == 1)        //second 48
  {
    one();
    x = x-10;
  }
  else
  {
    zero();
  }

  mark();              //second 49

  if(x/8 == 1)         //second 50
  {
    one();
    x = x-8;
  }
  else
  {
    zero();
  }

  if(x/4 == 1)         //second 51
  {
    one();
    x = x-4;
  }
  else
  {
    zero();
  }

  if(x/2 == 1)         //second 52
  {
    one();
    x = x-2;
  }
  else
  {
    zero();
  }

  if(x/1 == 1)         //second 53
  {
    one();
    x = x-1;
  }
  else
  {
    zero();
  }

  zero();              //second 54

  if(year%4 == 0)      //second 55 --  one if leap year, zero if not
  {
    one();
  }
  else
  {
    zero();
  }

  zero();              //second 56 -- no leap second warning

  if( dstwarn == 1)
  {                    //second 57 -- DST change warning
    one();
  }
  else
  {
    zero();
  }
  
  if( dst == 1)
  {                    //second 58 -- make DST change
    one();
  }
  else
  {
    zero();
  }

  mark();              //second 59
}

void mark()            // constructs and sends the BCD code element MARK
{
  digitalWrite(2,LOW);
  delay(800);
  digitalWrite(2,HIGH);
  delay(200);
}

void zero()            // constructs and sends the BCD code element ZERO
{
  digitalWrite(2,LOW);
  delay(200);
  digitalWrite(2,HIGH);
  delay(800);
}
    
void one()             // constructs and sends the BCD code element ONE
{
  digitalWrite(2,LOW);
  delay(500);
  digitalWrite(2,HIGH);
  delay(500);
}