Example Code for Arduino-Calibrate RTC with GNSS

Hardware Preparation

• Gravity: GNSS Position & Timing Module * 1
• DFRduino UNO R3 * 1
• Gravity: IO Expansion Shield * 1

Software Preparation

• Arduino IDE
• Download and install DFRobot_GNSS and RTC library

Wiring Diagram

Sample Code

/*!
 * @file gnssCalibRTC.ino
 * @brief Run this routine, calibration internal clock first, and then circularly get clock
 * @copyright    Copyright (c) 2010 DFRobot Co.Ltd (http://www.dfrobot.com)
 * @license      The MIT License (MIT)
 * @author [qsjhyy]([email protected])
 * @version V1.0
 * @date 2022-08-30
 * @url https://github.com/DFRobot/DFRobot_GNSSAndRTC
 */
#include "DFRobot_GNSSAndRTC.h"

#define I2C_COMMUNICATION  //use I2C for communication, but use the serial port for communication if the line of codes were masked

#ifdef  I2C_COMMUNICATION
DFRobot_GNSSAndRTC_I2C rtc(&Wire, MODULE_I2C_ADDRESS);
#else
/* ---------------------------------------------------------------------------------------------------------------------
      *    board   |             MCU                | Leonardo/Mega2560/M0 |    UNO    | ESP8266 | ESP32 |  microbit  |   m0  |
      *     VCC    |            3.3V/5V             |        VCC           |    VCC    |   VCC   |  VCC  |     X      |  vcc  |
      *     GND    |              GND               |        GND           |    GND    |   GND   |  GND  |     X      |  gnd  |
      *     RX     |              TX                |     Serial1 TX1      |     5     |   5/D6  |  D2   |     X      |  tx1  |
      *     TX     |              RX                |     Serial1 RX1      |     4     |   4/D7  |  D3   |     X      |  rx1  |
* ----------------------------------------------------------------------------------------------------------------------*/
/* Baud rate cannot be changed  */
#if defined(ARDUINO_AVR_UNO) || defined(ESP8266)
SoftwareSerial mySerial(4, 5);
DFRobot_GNSSAndRTC_UART rtc(&mySerial, UART_BAUDRATE);
#elif defined(ESP32)
DFRobot_GNSSAndRTC_UART rtc(&Serial1, UART_BAUDRATE,/*rx*/D2,/*tx*/D3);
#else
DFRobot_GNSSAndRTC_UART rtc(&Serial1, UART_BAUDRATE);
#endif
#endif

void setup()
{
	Serial.begin(115200);
	/*Wait for the chip to be initialized completely, and then exit*/
	while (!rtc.begin()) {
		Serial.println("Failed to init chip, please check if the chip connection is fine. ");
		delay(1000);
	}
	rtc.setHourSystem(rtc.e24hours);//Set display format

	/**
	 * @brief Calibrate RTC immediately with GNSS
	 * @note This is a single calibration;
	 * @n If the GNSS module signal is weak, time calibration may encounter issues.
	 * @return None
	 */
	// rtc.calibRTC();

	/**
	* @brief The loop automatically performs GNSS timing based on the set interval
	* @param hour Automatic calibration of the time interval. range: 0~255, unit: hour.
	* @note When set to zero, automatic time calibration is disabled.
	* @n Enabling it will trigger an immediate calibration.
	* @n If the GNSS module signal is weak, time calibration may encounter issues.
	* @return None
	*/
	rtc.calibRTC(1);
}
	uint8_t underCalibCount = 0;
    
void loop()
{
	/**
	* @brief Current clock calibration status
	* @param mode By default, it is set to true, indicating access to the calibration status only.
	* @n  If continuous calibration for one minute does not return a successful calibration,
	* @n  you can pass in false to manually terminate this calibration session.
	* @return uint8_t type, indicates current clock calibration status
	* @retval 0 Not calibrated
	* @retval 1 Calibration complete
	* @retval 2 Under calibration
	* @note Note: To avoid affecting subsequent calibration status,
	* @n    "Calibration completed Status (1)" is automatically zeroed after a successful read
	*/
	uint8_t status = rtc.calibStatus();
	if (DFRobot_GNSSAndRTC::eCalibComplete == status) {
		underCalibCount = 0;
		Serial.println("Calibration success!");
	} else if (DFRobot_GNSSAndRTC::eUnderCalib == status) {
		underCalibCount += 1;
		if (60 <= underCalibCount) {   // If the calibration fails for a long time, manually terminate the calibration
			rtc.calibStatus(false);
			underCalibCount = 0;
			Serial.println("Calibration failed!");
			Serial.println("It may be due to weak satellite signals.");
			Serial.println("Please proceed to an open outdoor area for time synchronization.");
		}
	}
	DFRobot_GNSSAndRTC::sTimeData_t sTime;
	sTime = rtc.getRTCTime();
	Serial.print(sTime.year, DEC);//year
	Serial.print('/');
	Serial.print(sTime.month, DEC);//month
	Serial.print('/');
	Serial.print(sTime.day, DEC);//day
	Serial.print(" (");
	Serial.print(sTime.week);//week
	Serial.print(") ");
	Serial.print(sTime.hour, DEC);//hour
	Serial.print(':');
	Serial.print(sTime.minute, DEC);//minute
	Serial.print(':');
	Serial.print(sTime.second, DEC);//second
	Serial.println(' ');
	/*Enable 12-hour time format*/
	// Serial.print(rtc.getAMorPM());
	// Serial.println();
        
	// In addition to data acquisition and other time consuming, the delay of 900ms makes each loop closer to 1 second
	delay(900);
}

Result