#include <PCF8574.h>

PCF8574 pcf20(0x20);

void setup() {
  Serial.begin(115200);

  Serial.print("PCF8574_LIB_VERSION:\t");
  Serial.println(PCF8574_LIB_VERSION);

  if (!pcf20.begin()) {
    Serial.println("Chip not responding.");
  }

  if (!pcf20.isConnected()) {
    Serial.println("could not initialize... => not connected");
    while (1);
  }

  uint8_t value = pcf20.read8();

  Serial.print("0x20 read: ");
  Serial.println(value, HEX);
}

void loop() {

  for (int i = 0; i < 255; i++) {
    pcf20.write8(i);
    delay(100);
  }

  pcf20.write(0, 1);

  for (int i = 0; i < 7; i++) {
    pcf20.shiftLeft();
    delay(100);
  }

  for (int i = 0; i < 7; i++) {
    pcf20.shiftRight();
    delay(100);
  }

  for (int i = 0; i < 8; i++) {
    pcf20.write(i, 1);
    delay(100);
    pcf20.write(i, 0);
    delay(100);
  }

  for (int i = 0; i < 8; i++) {
    pcf20.toggle(i);
    delay(100);
    pcf20.toggle(i);
    delay(100);
  }

  // Echo the state of the lines on the other PCF
  uint8_t value = pcf20.read8();
  pcf20.write8(value);
  delay(100);
}