//****************Libraries and variables********************

#include "RTClib.h"
RTC_PCF8523 rtc;

char daysOfTheWeek[7][12] = {"Su", "Mo", "Tu", "Wed", "Th", "Fr", 
"Sa"};

#include  //load sd library
#include //load SPI comminication library
int chipSelect = 10; //set chipSelect.
File mySensorData; //variable for working with our file object

#include 
Adafruit_LiquidCrystal lcd(0);
#include "DHT.h"
#define DHTPIN 2 //the pin we are connected to
#define DHTTYPE DHT22 //(AM2302)
#include "Wire.h"
#include "Adafruit_BMP085.h"

Adafruit_BMP085 bmp;//create an instance

DHT dht(DHTPIN, DHTTYPE); //create an instance

long b1=0;//variable to hold first reading
long b2=0;
long b3;//variable to hold the second reading
long delta=0;//variable to hold the change.
int i=0;
void setup() {
Serial.begin(9600);
dht.begin(); //begin is a function in dht
bmp.begin();
lcd.begin(16, 4);
SD.begin(chipSelect); //initialize the SD card with chipselect 
connected to pin 4

//***********************clock***********************
#ifndef ESP8266
while (!Serial); // wait for serial port to connect. Needed for 
native USB
#endif

if (! rtc.begin()) {
Serial.println("Couldn't find RTC");
Serial.flush();
abort();
}

if (! rtc.initialized() || rtc.lostPower()) {
Serial.println("RTC is NOT initialized, let's set the time!");
// When time needs to be set on a new device, or after a power 
loss, the
// following line sets the RTC to the date & time this sketch was 
compiled
rtc.adjust(DateTime(F(__DATE__), F(__TIME__)));
// This line sets the RTC with an explicit date & time, for 
example to set
// January 21, 2014 at 3am you would call:
// rtc.adjust(DateTime(2014, 1, 21, 3, 0, 0));
//
// Note: allow 2 seconds after inserting battery or applying 
external power
// without battery before calling adjust(). This gives the 
PCF8523's
// crystal oscillator time to stabilize. If you call adjust() 
very quickly
// after the RTC is powered, lostPower() may still return true.
}

// When time needs to be re-set on a previously configured 
device, the
// following line sets the RTC to the date & time this sketch was 
compiled
// rtc.adjust(DateTime(F(__DATE__), F(__TIME__)));
// This line sets the RTC with an explicit date & time, for 
example to set
// January 21, 2014 at 3am you would call:
// rtc.adjust(DateTime(2014, 1, 21, 3, 0, 0));

// When the RTC was stopped and stays connected to the battery, 
it has
// to be restarted by clearing the STOP bit. Let's do this to 
ensure
// the RTC is running.
rtc.start();

// The PCF8523 can be calibrated for:
//        - Aging adjustment
//        - Temperature compensation
//        - Accuracy tuning
// The offset mode to use, once every two hours or once every 
minute.
// The offset Offset value from -64 to +63. See the Application 
Note for calculation of offset values.
// https://www.nxp.com/docs/en/application-note/AN11247.pdf
// The deviation in parts per million can be calculated over a 
period of observation. Both the drift (which can be negative)
// and the observation period must be in seconds. For accuracy 
the variation should be observed over about 1 week.
// Note: any previous calibration should canceled prior to any 
new observation period.
// Example - RTC gaining 43 seconds in 1 week
float drift = 43; // seconds plus or minus over observation 
period - set to 0 to cancel previous calibration.
float period_sec = (7 * 86400);  // total observation period 
in seconds (86400 = seconds in 1 day:  7 days = (7 * 86400) 
seconds )
float deviation_ppm = (drift / period_sec * 1000000); //  
deviation in parts per million (μs)
float drift_unit = 4.34; // use with offset mode PCF8523_TwoHours
// float drift_unit = 4.069; //For corrections every min the 
drift_unit is 4.069 ppm (use with offset mode PCF8523_OneMinute)
int offset = round(deviation_ppm / drift_unit);
// rtc.calibrate(PCF8523_TwoHours, offset); // Un-comment to 
perform calibration once drift (seconds) and observation period 
(seconds) are correct
// rtc.calibrate(PCF8523_TwoHours, 0); // Un-comment to cancel 
previous calibration

Serial.print("Offset is "); 
Serial.println(offset); // Print to control offset
//*****************************clock****************************
}

void loop() {

float h = dht.readHumidity();
float t = dht.readTemperature(); //Celsius

delay(10000);
lcd.clear();

if (isnan(h) || isnan(t)) {
Serial.println("Failed to read from FHT sensor!");
return;
}
if (!bmp.begin()) {
Serial.println("Could not find a valid BMP085 sensor, check 
wiring!");
while (1) {}
}



Serial.print("Pressure= ");
Serial.print(bmp.readPressure());

Serial.print( " Pa");
//Serial.print(" Start ");
Serial.print(" ");
Serial.print(b1);
Serial.print(" ");
Serial.print(b3);
Serial.print(" D ");
Serial.println(delta);

Serial.print("Baro Temp= ");
Serial.print(bmp.readTemperature() * 9 / 5 + 32);
Serial.println(" F ");

Serial.print("Humidity: ");
Serial.print(h);
Serial.println("%\t");

Serial.println();

//*******************Print to monitor************************
DateTime now = rtc.now();

Serial.print(now.year(), DEC);
Serial.print('/');
Serial.print(now.month(), DEC);
Serial.print('/');
Serial.print(now.day(), DEC);
Serial.print(" (");
Serial.print(daysOfTheWeek[now.dayOfTheWeek()]);
Serial.print(") ");
Serial.print(now.hour(), DEC);
Serial.print(':');
Serial.print(now.minute(), DEC);
Serial.print(':');
Serial.print(now.second(), DEC);
Serial.println();


//************************Write to the LCD display*************
lcd.setCursor(0, 0);
lcd.print(now.year(), DEC);
lcd.print('/');
lcd.print(now.month(), DEC);
lcd.print('/');
lcd.print(now.day(), DEC);
lcd.print("(");
lcd.print(daysOfTheWeek[now.dayOfTheWeek()]);
lcd.print(")");
lcd.print(now.hour(), DEC);
lcd.print(':');
lcd.print(now.minute(), DEC);

lcd.setCursor(0, 1);
lcd.print(bmp.readTemperature() * 9 / 5 + 32);
lcd.print(" F");

lcd.setCursor(0, 2);
lcd.print(bmp.readPressure());
lcd.print(" Pa");
lcd.print(" Del ");
lcd.print(delta);

lcd.setCursor(0, 3);
lcd.print(h);
lcd.print(" %RH");

//this code is used to check the change in barometric pressure 
for a given time interval

Serial.print(now.year(), DEC);
Serial.print('/');
Serial.print(now.month(), DEC);
Serial.print('/');
Serial.print(now.day(), DEC);
Serial.print(" (");
Serial.print(daysOfTheWeek[now.dayOfTheWeek()]);
Serial.print(") ");
Serial.print(now.hour(), DEC);
Serial.print(':');
Serial.print(now.minute(), DEC);
Serial.print(':');
Serial.print(now.second(), DEC);
Serial.println();
i=i+1;
Serial.println(i);
//readings are refreshed every 10 seconds. 
//this will happen 360 times in one hour. 
//when the count is greater than 359, or 360, the second reading 
is compared to the one
//taken at the beginning of the time interval. Change the value 
of the test count-1 to 
//use a different time interval.
if(i>359){  //creates a time between readings of one hour. 
Serial.println("now writing to disk");

//********************Write to the SD card*******************
mySensorData = SD.open("PTData.txt", FILE_WRITE); //open 
FTData.txt on the SD card as a file to write to
if (mySensorData) { //if file opens

DateTime now = rtc.now();

mySensorData.print(now.year(), DEC);
mySensorData.print('/');
mySensorData.print(now.month(), DEC);
mySensorData.print('/');
mySensorData.print(now.day(), DEC);
mySensorData.print(" (");
mySensorData.print(daysOfTheWeek[now.dayOfTheWeek()]);
mySensorData.print(") ");
mySensorData.print(now.hour(), DEC);
mySensorData.print(',');
mySensorData.print(now.minute(), DEC);
mySensorData.print(",");
mySensorData.print(bmp.readTemperature() * 9 / 5 + 32); //write 
temperature to SD card.
mySensorData.print(",");
mySensorData.print(bmp.readPressure());//write pressure
mySensorData.print(",");
mySensorData.println(h);//write humidity
mySensorData.close(); //close the file

}
i=0;
b2=bmp.readPressure();
delta=b1-b2;//display change relative to one hour prior

b1=b2;

}

}