https://www.twovolt.com/2020/05/02/arduino-4-digit-7-segment-multiplexed-display-board-using-atmega328-chip/

ARDUINO 4 DIGIT 7 SEGMENT MULTIPLEXED DISPLAY BOARD USING ATMEGA328 CHIP

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#include <EEPROM.h>

#define bt_up     A0

#define bt_down   A1

#define bt_reset  A2

#define buzzer 13

#define data_pin  2

#define clock_pin 3

                       /*0*/ /*1*/ /*2*/ /*3*/ /*4*/ /*5*/ /*6*/ /*7*/ /*8*/ /*9*/

const int digits[] = { 0x3f, 0x06, 0x5b, 0x4f, 0x66, 0x6d, 0x7d, 0x07, 0x7f, 0x6f };

                         // 12%,  25%,  38%,  50%,  63%,  75%,  88%, 100% 

const int Brightness[] = { 0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f};

long Counter=0;

int flag1=0, flag2=0, timer=0;

void setup(){ // put your setup code here, to run once  

pinMode(bt_up,    INPUT_PULLUP);

pinMode(bt_down,  INPUT_PULLUP);

pinMode(bt_reset, INPUT_PULLUP);

pinMode(buzzer, OUTPUT);

pinMode(clock_pin, OUTPUT);

pinMode(data_pin, OUTPUT);

start();

writeValue(Brightness[6]); // set Brightness 0 to 7

stop();

// clear display

write_data(0x00, 0x00, 0x00, 0x00);

//Indicate that system is ready

for (int i = 9; i >=0; i–) {

write_data(digits[i%10], digits[i%10], digits[i%10], digits[i%10]);

 delay(1000); 

}

if(EEPROM.read(0)==0){}

else{

eeprom_write();

EEPROM.write(0, 0);

}

eeprom_read(); 

}

void loop(){  

if(digitalRead(bt_up) == 0){ 

if(flag1==0){ flag1=1;

digitalWrite(buzzer, HIGH);

Counter = Counter+1;

if(Counter>9999){Counter=0;} 

eeprom_write();

delay(100); 

 }

}else{flag1=0;}

if(digitalRead(bt_down) == 0){ 

if(flag2==0){ flag2=1;

digitalWrite(buzzer, HIGH);

Counter = Counter-1;

if(Counter<0){Counter=9999;}

eeprom_write();

delay(100);  

 }  

}else{flag2=0;}

if(digitalRead(bt_reset) == 0){ 

digitalWrite(buzzer, HIGH);

if(timer<100){timer=timer+1;}

if(timer==100){

Counter=0;

eeprom_write(); 

 }   

}else{timer=0;}

write_data(digits[(Counter/1000)%10], digits[(Counter/100)%10], digits[(Counter/10)%10], digits[Counter%10]);

delay(10); 

digitalWrite(buzzer, LOW);

}

void eeprom_write(){ 

EEPROM.write(1,  Counter%10);

EEPROM.write(2, (Counter/10)%10);

EEPROM.write(3, (Counter/100)%10);

EEPROM.write(4, (Counter/1000)%10);

}

void eeprom_read(){

Counter=EEPROM.read(4)*1000+EEPROM.read(3)*100+EEPROM.read(2)*10+EEPROM.read(1);

}

void write_data(uint8_t dig1, uint8_t dig2, uint8_t dig3, uint8_t dig4){

  start();

  writeValue(0x40);

  stop();

  start();

  writeValue(0xc0);

  writeValue(dig1);

  writeValue(dig2);

  writeValue(dig3);

  writeValue(dig4);

  stop();

}

void start(void){

  digitalWrite(clock_pin,HIGH);//send start signal to TM1637

  digitalWrite(data_pin,HIGH);

  delayMicroseconds(5);

  digitalWrite(data_pin,LOW);

  digitalWrite(clock_pin,LOW);

  delayMicroseconds(5);

}

void stop(void){

  digitalWrite(clock_pin,LOW);

  digitalWrite(data_pin,LOW);

  delayMicroseconds(5);

  digitalWrite(clock_pin,HIGH);

  digitalWrite(data_pin,HIGH);

  delayMicroseconds(5);

}

bool writeValue(uint8_t value){

  for(uint8_t i = 0; i < 8; i++){

    digitalWrite(clock_pin, LOW);

    delayMicroseconds(5);

    digitalWrite(data_pin, (value & (1 << i)) >> i);

    delayMicroseconds(5);

    digitalWrite(clock_pin, HIGH);

    delayMicroseconds(5);

  }

  // wait for ACK

  digitalWrite(clock_pin,LOW);

  delayMicroseconds(5);

  pinMode(data_pin,INPUT);

  digitalWrite(clock_pin,HIGH);

  delayMicroseconds(5);

  bool ack = digitalRead(data_pin) == 0;

  pinMode(data_pin,OUTPUT);

  return ack;

}