#include <Wire.h>

unsigned char z=0;
byte port_rd;
#define adr 0x40

void setup() {
  // put your setup code here, to run once:
Serial.begin(115200);
  Wire.begin();

  Wire.beginTransmission(adr);
Wire.write(255);//accende tutti
Wire.endTransmission();
delay(5000);

  Wire.beginTransmission(adr);
Wire.write(0);//spegne tutti
Wire.endTransmission();

}

void loop() {
     Wire.beginTransmission(adr);
    Wire.requestFrom(adr, 1);    // request 1 bytes from PCF8574 at address 0x20
     if (Wire.available()) {
     port_rd = Wire.read();   // receive byte
     }
    Serial.println(port_rd, BIN); // print byte in binary format
    Wire.endTransmission(); // stop transmitting
  // put your main code here, to run repeatedly:


Wire.beginTransmission(adr);
Wire.write(z);
Wire.endTransmission();
delay(100);

if(z!=255)z++;


}