int row_pins[4] = {18,17,16,15};
int col_pins[4] = {7,6,5,4};

int row_ls[4] = {38,37,36,35};
int col_ls[4] = {0,45,48,47};

char key;
char last_key;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);

  for(int i=0;i<4;i++){
    pinMode(row_pins[i], INPUT_PULLUP);
    pinMode(col_pins[i], OUTPUT);
    digitalWrite(col_pins[i], HIGH);
  }
  for(int i=0;i<4;i++){
    pinMode(row_ls[i], OUTPUT);
    pinMode(col_ls[i], OUTPUT);
    digitalWrite(row_ls[i], LOW);
    digitalWrite(col_ls[i], LOW);
  }
}
void turn_on(int row,int col){

  for(int i=0;i<4;i++){
    digitalWrite(row_ls[i], HIGH);
    digitalWrite(col_ls[i], LOW);
  }
  if(row >=0) digitalWrite(row_ls[row], LOW);
  if(col >=0) digitalWrite(col_ls[col], HIGH);
  
}
char read_keypad(){
  char keys[4][4] = {
    {'1','2','3','A'},
    {'4','5','6','B'},
    {'7','8','9','C'},
    {'*','0','#','D'}
  };
  for(int j =0;j<4;j++){
    digitalWrite(col_pins[j], LOW);
    for(int i=0;i<4;i++){
      if(digitalRead(row_pins[i]) == LOW){
        digitalWrite(col_pins[j], HIGH);
        turn_on(i,j);
        return keys[i][j];
      }
    }
    digitalWrite(col_pins[j], HIGH);
  }
  return NULL;
}

void loop() {
  key = read_keypad();
  if(key && (last_key != key)){
    last_key = key;
    Serial.printf("检测到按键：%c 按下\n",key);
  }
}