Arduino_Serial_RCV

#define Pin1 4
#define Pin2 5
#define Pin3 6
#define Pin4 7
#define Pin5 8
#define Pin6 9
#define Pin7 10
#define Pin8 11
#define Pin9 12
#define Pin10 13

bool swt1, swt2, swt3, swt4, swt5, swt6, swt7, swt8, swt9, swt10;

void setup() {
  pinMode(Pin1, OUTPUT);
  pinMode(Pin2, OUTPUT);
  pinMode(Pin3, OUTPUT);
  pinMode(Pin4, OUTPUT);
  pinMode(Pin5, OUTPUT);
  pinMode(Pin6, OUTPUT);
  pinMode(Pin7, OUTPUT);
  pinMode(Pin8, OUTPUT);
  pinMode(Pin9, OUTPUT);
  pinMode(Pin10, OUTPUT);
  Serial.begin(9600);
  while (!Serial);
}

void loop() {
  if (Serial.available() > 0) {
    char cmd = Serial.read();
    if (cmd == 'a') {
      swt1 = !swt1;
    }
    if (cmd == 'b') {
      swt2 = !swt2;
    }
    if (cmd == 'c') {
      swt3 = !swt3;
    }
    if (cmd == 'd') {
      swt4 = !swt4;
    }
    if (cmd == 'e') {
      swt5 = !swt5;
    }
    if (cmd == 'f') {
      swt6 = !swt6;
    }
    if (cmd == 'g') {
      swt7 = !swt7;
    }
    if (cmd == 'h') {
      swt8 = !swt8;
    }
    if (cmd == 'i') {
      swt9 = !swt9;
    }
    if (cmd == 'j') {
      swt10 = !swt10;
    }
  }
  Serial.flush();
  digitalWrite(Pin1, swt1);
  digitalWrite(Pin2, swt2);
  digitalWrite(Pin3, swt3);
  digitalWrite(Pin4, swt4);
  digitalWrite(Pin5, swt5);
  digitalWrite(Pin6, swt6);
  digitalWrite(Pin7, swt7);
  digitalWrite(Pin8, swt8);
  digitalWrite(Pin9, swt9);
  digitalWrite(Pin10, swt10);
}