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| // Date and time functions using a PCF8523 RTC connected via I2C and Wire lib
#include "RTClib.h"
RTC_PCF8523 rtc;
char daysOfTheWeek[7][12] = {"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"};
void setup () {
Serial.begin(9600);
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 cancelled prior to any new observation period.
// Example - RTC gaining 43 seconds in 1 week
float drift = 43; // seconds plus or minus over oservation period - set to 0 to cancel previous calibration.
float period_sec = (7 \* 86400); // total obsevation 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
}
void loop () {
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();
delay(1000);
}
|
