// C++ code
//

// 初始接腳
int rows[]={18,5,17,16};
int cols[]={4,0,2,15};
int row=4;
int col=4;
int i,x,y;
char tbl[]={'1','2','3','A',
            '4','5','6','B',
            '7','8','9','C',
            '*','0','#','D'};
/*
x,y 00 '1'
x,y 10 '4'
x,y 23 'C'
x,y 33 'D'
====>x*4+y
*/
void setup()
{
  Serial.begin(9600);
  for (i=0;i<row;i++)
    pinMode(rows[i], OUTPUT);
  for (i=0;i<col;i++)
    pinMode(cols[i], INPUT_PULLUP);
   Serial.begin(9600);
}

bool test,old=false;
void loop()
{
  
  test=scan();
  if (test==1 && old==0){
    //Serial.print(x);
    //Serial.println(y);
    Serial.println(tbl[x*4+y]);
  }
  old=test;
}
bool  scan()
{
  bool Pressed=false;
  //scan row[0]
  digitalWrite(rows[0],LOW);
  digitalWrite(rows[1],HIGH);
  digitalWrite(rows[2],HIGH);
  digitalWrite(rows[3],HIGH);
  for (int i=0;i<col;i++)
    if (digitalRead(cols[i])==0){
      Pressed=true;
      x=0;y=i;
      return Pressed;
    }    
  //scan row[1] 
  digitalWrite(rows[0],HIGH);
  digitalWrite(rows[1],LOW);
  digitalWrite(rows[2],HIGH);
  digitalWrite(rows[3],HIGH);
  for (int i=0;i<col;i++)
    if (digitalRead(cols[i])==0){
      Pressed=true;
      x=1;y=i;
      return Pressed;
    }    
      
  //scan row[2]
  digitalWrite(rows[0],HIGH);
  digitalWrite(rows[1],HIGH);
  digitalWrite(rows[2],LOW);
  digitalWrite(rows[3],HIGH);
  for (int i=0;i<col;i++)
    if (digitalRead(cols[i])==0){
      Pressed=true;
      x=2;y=i;
      return Pressed;
    }    
  //scan row[3] 
  digitalWrite(rows[0],HIGH);
  digitalWrite(rows[1],HIGH);
  digitalWrite(rows[2],HIGH);
  digitalWrite(rows[3],LOW);
  for (int i=0;i<col;i++)
    if (digitalRead(cols[i])==0){
      Pressed=true;
      x=3;y=i;
      return Pressed;
    }
  digitalWrite(rows[0],HIGH);
  digitalWrite(rows[1],HIGH);
  digitalWrite(rows[2],HIGH);
  digitalWrite(rows[3],HIGH);
 return Pressed;
}