Expander

int InterruptPIN = 17;
boolean keyChanged = false;
void InterruptOnIn(){keyChanged = true;}

PCF8574 ExtOuts(0x20);
PCF8574 ExtIns(0x21);

static const inline void Setup_Expanders(){
    for(int i=0;i<8;i++) {ExtOuts.pinMode(i, OUTPUT);}
    ExtOuts.begin();

    pinMode(InterruptPIN, INPUT_PULLUP);
    attachInterrupt(digitalPinToInterrupt(InterruptPIN), InterruptOnIn, FALLING);

    for(int i=0;i<8;i++) {ExtIns.pinMode(i, INPUT);}
    ExtIns.begin();

    for(int i=0;i<8;i++) {ExtOuts.digitalWrite(i, HIGH);delay(100);}
    for(int i=8;i>=0;i--) {ExtOuts.digitalWrite(i, LOW);delay(100);}
}


static const inline void Expander_Loop(){
  if (keyChanged){
    PCF8574::DigitalInput val = ExtIns.digitalReadAll();
    if (val.p0==HIGH) Serial.println("KEY0 PRESSED");
    if (val.p1==HIGH) Serial.println("KEY1 PRESSED");
    if (val.p2==HIGH) Serial.println("KEY2 PRESSED");
    if (val.p3==HIGH) Serial.println("KEY3 PRESSED");
    if (val.p4==HIGH) Serial.println("KEY4 PRESSED");
    if (val.p5==HIGH) Serial.println("KEY5 PRESSED");
    if (val.p6==HIGH) Serial.println("KEY6 PRESSED");
    if (val.p7==HIGH) Serial.println("KEY7 PRESSED");
    keyChanged = false;
  }
}