#include <SoftwareSerial.h>
SoftwareSerial swSerial(4, 5); // RX=4, TX=5

const int MY_BUTTON = 2;
const int MY_LED = 10;
const int BUILTIN_LED = LED_BUILTIN;

bool myLedState = false;
bool lastButtonState = HIGH;

void setup() {
  pinMode(MY_BUTTON, INPUT_PULLUP);
  pinMode(MY_LED, OUTPUT);
  pinMode(BUILTIN_LED, OUTPUT);
  swSerial.begin(9600);
}

void loop() {
  if (swSerial.available() >= 2) {
    char cmd = swSerial.read();
    char val = swSerial.read();
    if (cmd == 'U') {
      myLedState = (val == 'T') ? !myLedState : (val == '1');
      digitalWrite(MY_LED, myLedState ? HIGH : LOW);
      digitalWrite(BUILTIN_LED, HIGH);
      delay(50);
      digitalWrite(BUILTIN_LED, LOW);
    }
  }

  bool curr = digitalRead(MY_BUTTON);
  if (lastButtonState == HIGH && curr == LOW) {
    swSerial.write('N');
    swSerial.write('T');
    digitalWrite(BUILTIN_LED, HIGH);
    delay(50);
    digitalWrite(BUILTIN_LED, LOW);
    delay(50);
  }
  lastButtonState = curr;
}