DTMF Decoder

/*
* Project name:
DTMF Decoder
* Copyright
(c) Researchdesignlab.com
* Description:

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

*/

int sda=5;
int d1=2;
int d2=3;
int d3=4;
int d4=5;

void setup()
{
pinMode(d1,INPUT);
pinMode(d2,INPUT);
pinMode(d3,INPUT);
pinMode(d4,INPUT);
Serial.begin(9600);
}

void loop()
{
if(sda==LOW)
{
delay(200);
if((d1==HIGH) && (d2==LOW) && (d3==LOW) && (d4==LOW))
{
Serial.println("1");
}
if((d1==LOW) && (d2==HIGH) && (d3==LOW) && (d4==LOW))
{
Serial.println("2");
}
if((d1==LOW) && (d2==HIGH) && (d3==HIGH) && (d4==LOW))
{
Serial.println("3");
}
if((d1==LOW) && (d2==HIGH) && (d3==LOW) && (d4==LOW))
{
Serial.println("4");
}
if((d1==LOW) && (d2==HIGH) && (d3==LOW) && (d4==LOW))
{
Serial.println("5");
}
if((d1==LOW) && (d2==HIGH) && (d3==LOW) && (d4==LOW))
{
Serial.println("6");
}
if((d1==HIGH) && (d2==HIGH) && (d3==HIGH) && (d4==LOW))
{
Serial.println("7");
}
if((d1==LOW) && (d2==LOW) && (d3==LOW) && (d4==HIGH))
{
Serial.println("8");
}
if((d1==HIGH) && (d2==LOW) && (d3==LOW) && (d4==HIGH))
{
Serial.println("9");
}
if((d1==LOW) && (d2==HIGH) && (d3==LOW) && (d4==HIGH))
{
Serial.println("0");
}
}
}