PCF8574A I2C I/O routine

PCF8574A.pde

/******************************************************************************
 *  PCF8574A I2C Output
 *
 *  Prototype I2C interface to PCF8574A I/O Expander.
 *
 *  Arduino analog input 5 - I2C SCL
 *  Arduino analog input 4 - I2C SDA
 *
 ******************************************************************************/

// Up to 8 devices can share the same I2C bus starting from address 38h to 3Fh
// hexadecimal (56 to 63 decimal)
#define  DEVICE_ADDRESS  56

#include <Wire.h>

void setup()
{
  Wire.begin();                   // Join I2C bus
  deviceWrite(B11111111);         // Set all LEDs off
}

void loop()
{
  deviceWrite(B11111001);         // Turn on LEDs connected to P1 and P2
                                  // Turn off LED connected to P0
  delay(1000);                    // Delay 1 second
  deviceWrite(B11111110);         // Turn off LEDs connected to P1 and P2
                                  // Turn on LED connected to P0
  delay(1000);                    // Delay 1 second
}

void deviceWrite(byte txData)
{
  Wire.beginTransmission(DEVICE_ADDRESS);
  Wire.send(txData);
  Wire.endTransmission();
}