PCF8591 AD/DA Converter Module

/*
* Project name:
PCF8591 AD/DA Converter Module
* Copyright
(c) Researchdesignlab.com
* Description:

* Test configuration:
MCU: ATMEGA328
Dev.Board: Arduino uno
Oscillator: 16 MHz
Software: Arduino

*/

#include <Wire.h>
#define PCF8591 (0x90 >> 1) // I2C bus address
#define ADC0 0x00 // control bytes for reading individual ADCs
#define ADC1 0x01
#define ADC2 0x02
#define ADC3 0x03
byte value0, value1, value2, value3;
void setup()
{
Wire.begin();
Serial.begin(9600);
}
void loop()
{
Wire.beginTransmission(PCF8591); // wake up PCF8591
Wire.write(ADC0); // control byte - read ADC0
Wire.endTransmission(); // end tranmission
Wire.requestFrom(PCF8591, 2);
value0=Wire.read();
value0=Wire.read();
Wire.beginTransmission(PCF8591); // wake up PCF8591
Wire.write(ADC1); // control byte - read ADC1
Wire.endTransmission(); // end tranmission
Wire.requestFrom(PCF8591, 2);
value1=Wire.read();
value1=Wire.read();
Wire.beginTransmission(PCF8591); // wake up PCF8591
Wire.write(ADC2); // control byte - read ADC2
Wire.endTransmission(); // end tranmission
Wire.requestFrom(PCF8591, 2);
value2=Wire.read();
value2=Wire.read();
Wire.beginTransmission(PCF8591); // wake up PCF8591
Wire.write(ADC3); // control byte - read ADC3
Wire.endTransmission(); // end tranmission
Wire.requestFrom(PCF8591, 2);
value3=Wire.read();
value3=Wire.read();
Serial.print(value0); Serial.print(" ");
Serial.print(value1); Serial.print(" ");
Serial.print(value2); Serial.print(" ");
Serial.print(value3); Serial.print(" ");
Serial.println();
delay(1000);
}