/*
  http://www.bristolwatch.com/arduino/arduino6.htm
  PCA9555 32-Bit GPIO Expander with Arduino
  by Lewis Loflin lewis@bvu.net
*/



#include <Wire.h> // specify use of Wire.h library.

int i;
byte temp1;
void setup()

{
  pinMode(2, INPUT);  // IRQ input
  Wire.begin();
  Wire.beginTransmission(0x20);  // setup out direction registers
  Wire.write(0x06);  // pointer
  Wire.write(0x0F);  // DDR Port0 bits 0-3 input 4-7 output 
  Wire.write(0x00);  // DDR Port1 all output
  Wire.endTransmission(); 

  Wire.beginTransmission(0x20);  // 
  Wire.write(0x02);  // pointer
  Wire.write(0x00);  // clear bits 4-7 PORT0
  Wire.endTransmission(); 

  Wire.beginTransmission(0x20);  // invert bit
  Wire.write(0x04);  // pointer
  Wire.write(0xFF);  // invert bits PORT0 on read
  Wire.endTransmission(); 

  // clear LEDs PORT1
  Wire.beginTransmission(0x20);  
  Wire.write(0x03); // begin here
  Wire.write(temp1); 
  Wire.endTransmission();


  // Use 0x21 for LCD display.

  Wire.beginTransmission(0x21);  // setup out direction registers
  Wire.write(0x06);  // pointer
  Wire.write(0x00);  // DDR Port1 all output 
  Wire.write(0x00);  // DDR Port1 all output
  Wire.endTransmission(); 

  // setup port 0 D7 = E; D6 = RS 
  Wire.beginTransmission(0x21); 
  Wire.write(0x02); //pointer
  Wire.write(B10000000); // setup for command mode
  Wire.endTransmission(); 


}  // end setup

void loop() {

  i++; 
  // LEDs to GND PORT 1
  Wire.beginTransmission(0x20);  
  Wire.write(0x03); // begin here
  Wire.write(i); 
  Wire.endTransmission();

  if (i > 255) i = -1;
  delay(500); // delay 500 mSec.

} // end loop