tinkercad PCF8574 I2C reader + 74HC4017 decade couter

#include <Wire.h>

void setup()

{

  TCCR1A = 0b00000000; //TCCR1A bit 0, 1 and TCCR1B bit 3, 4 set timer mode

  TCCR1B = 0b00001101; //Set mode to be clear on compare. set scaler to be clock/1024

  OCR1A = 7811; //period = (OCR1A/B + 1)*scaler*62.5ns = 0.5s

  TIMSK1 = 0b00000010; //enable timer counter

  sei();

  

  Wire.begin();

  Serial.begin(9600);

}

void loop()

{

  byte data;

  Wire.requestFrom(0x20, 1); //request 1 byte from I2C expander

  while(Wire.available()) {

data = Wire.read();

      Serial.print("reader1 data ");

      printBin(data);

      Serial.println();

}

  

  Wire.requestFrom(0x21, 1); //request 1 byte from I2C expander

  while(Wire.available()) {

data = Wire.read();

      Serial.print("reader2 data ");

      printBin(data);

      Serial.println();

}

  

  delay(1000);

}

ISR(TIMER1_COMPA_vect){

PORTC ^= 0b00000001; //toggle pin  6(shift register clock)

}

void printBin(byte aByte) {

  for (int8_t aBit = 7; aBit >= 0; aBit--)

    Serial.write(bitRead(aByte, aBit) ? '1' : '0');

}

Johnson decade counter

reference:

https://docs.arduino.cc/learn/communication/wire

Johnson decade counter

https://www.tinkercad.com/things/gNDxfQiPGge-copy-of-johnson-decade-counter/editel?tenant=circuits