这次的代码所使用的硬件上1602换成了IIC，不用复杂地接线了。

把1602和DS3231按如下接好即可：

VCC —— VCC

GND —— GND

SCL —— SCL/A5

SDA —— SDA/A4

#include <Wire.h>
#include <ds3231.h>
#include <LiquidCrystal_I2C_DS3231.h>
#define BUFF_MAX 128

//****************************************Define I2C LCD Display *********************************
#define I2C_ADDR    0x27  // Define I2C Address for the PCF8574T 
//---(Following are the PCF8574 pin assignments to LCD connections )----
// This are different than earlier/different I2C LCD displays

#define Rs_pin  0
#define Rw_pin  1
#define En_pin  2
#define BACKLIGHT_PIN  3
#define D4_pin  4
#define D5_pin  5
#define D6_pin  6
#define D7_pin  7

#define  LED_OFF  0
#define  LED_ON  1

/*-----( Declare objects )-----*/  
LiquidCrystal_I2C  lcd(I2C_ADDR,En_pin,Rw_pin,Rs_pin,D4_pin,D5_pin,D6_pin,D7_pin);
//************************************ END LCD DISPLAY *******************************************
//年
byte Nian[8] = {0b01000,0b01111,0b10010, 0b01111, 0b01010, 0b11111, 0b00010, 0b00010};
//月
byte Yue[8] = {0b01111, 0b01001, 0b01111, 0b01001, 0b01111, 0b01001, 0b10011, 0b00001};
//日
byte Ri[8] = {0b01111, 0b01001, 0b01001, 0b01111, 0b01001, 0b01001, 0b01111, 0b00000};

uint8_t time[8];
char recv[BUFF_MAX];
unsigned int recv_size = 0;
unsigned long prev, interval = 1000;

void setup()
{
    Serial.begin(9600);
    Wire.begin();
    DS3231_init(DS3231_INTCN);
    memset(recv, 0, BUFF_MAX);
    Serial.println("GET time");

  //**************************LCD Setup********************************
   lcd.begin (16,2);  // initialize the lcd 
   // Switch on the backlight
   lcd.setBacklightPin(BACKLIGHT_PIN,POSITIVE);
   lcd.setBacklight(LED_ON);
  //***************************END LCD Setup********************************
    
    Serial.println("Setting time");
   // setTheTime("304022129022016");     // ssmmhhWDDMMYYYY set time once in the given format
    lcd.createChar(0, Nian);
    lcd.createChar(1, Yue);
    lcd.createChar(2, Ri);
}

void loop()
{
    char tempF[6]; 
    float temperature;
    char buff[BUFF_MAX];
    unsigned long now = millis();
    struct ts t;
    // show time once in a while
    if (now - prev > interval){
        DS3231_get(&t); //Get time
        temperature = DS3231_get_treg(); //Get temperature
        dtostrf(temperature, 5, 1, tempF);

        lcd.clear();
        lcd.setCursor(0,0);
        
        lcd.print(t.year);
        lcd.write(byte(0));
        if(t.mon<10)
        {
          lcd.print("0");
        }
        lcd.print(t.mon);
         lcd.write(byte(1));
        if(t.mday<10)
        {
          lcd.print("0");
        }
        lcd.print(t.mday);
         lcd.write(byte(2));
        lcd.print("  ");
        printWeek(t.wday);     
                
        lcd.setCursor(0,1); //Go to second line of the LCD Screen
         if(t.hour<10)
        {
          lcd.print("0");
        }
        lcd.print(t.hour);
        lcd.print(":");
        if(t.min<10)
        {
          lcd.print("0");
        }
        lcd.print(t.min);
        lcd.print(":");
        if(t.sec<10)
        {
          lcd.print("0");
        }
        lcd.print(t.sec);
        
        lcd.print(' ');
        lcd.print(tempF);
        lcd.print((char)223);
        lcd.print("C");
        prev = now;
    }

}

void setTheTime(char *cmd)
{
    struct ts t;

    // ssmmhhWDDMMYYYY  set time

        t.sec = inp2toi(cmd, 0);
        t.min = inp2toi(cmd, 2);
        t.hour = inp2toi(cmd, 4);
        t.wday = inp2toi(cmd, 6);
        t.mday = inp2toi(cmd, 7);
        t.mon = inp2toi(cmd, 9);
        t.year = inp2toi(cmd, 11) * 100 + inp2toi(cmd, 13);
        DS3231_set(t);
        Serial.println("OK");
}


void printWeek(int week)
{
  switch(week)
  {
    case 1: lcd.print("Mon");break;
    case 2: lcd.print("Tue");break;
    case 3: lcd.print("Wed");break;
    case 4: lcd.print("Thu");break;
    case 5: lcd.print("Fri");break;
    case 6: lcd.print("Sat");break;
    case 7: lcd.print("Sun");break;
    default: lcd.print(" Error ");break;
  } 
}

原始代码和库来源：https://www.youtube.com/watch?v=eDUueSq_mcg