Using the Pmod R2R with Arduino Uno

/************************************************************************
*
* Test of the Pmod 
*
*************************************************************************
* Description: Pmod_R2R
* The output voltage is adjustable according to the logic levels
* applied to pins 2 to 9 of the Arduino.
* The output voltage is the sum of all components.
*
* Material
* 1. Arduino Uno
* 2. Pmod R2R 
*
************************************************************************/

void setup()
{
 for (int i=2; i<=9; i++) // configuration ofpins 2 to 9 as output
 {
  pinMode(i,OUTPUT);
 }
}

void loop()
{
 // Input D7 of the module in the high state imposes a component of VCC/2
 digitalWrite(9,HIGH);
 // Input D6 of the module in the high state imposes a component of VCC/4
 digitalWrite(8,LOW);
 // Input D5 of the module in the high state imposes a component of VCC/8
 digitalWrite(7,LOW);
 // Input D4 of the module in the high state imposes a component of VCC/16
 digitalWrite(6,LOW);
 // Input D3 of the module in the high state imposes a component of VCC/32
 digitalWrite(5,HIGH);
 // Input D2 of the module in the high state imposes a component of VCC/64
 digitalWrite(4,HIGH);
 // Input D1 of the module in the high state imposes a component of VCC/128
 digitalWrite(3,HIGH);
 // Input D0 of the module in the high state imposes a component of VCC/256
 digitalWrite(2,HIGH);
}