#include <WiFi.h>
#include <esp_now.h>

const int ledPin = D4;

void onDataRecv(const esp_now_recv_info_t* recv_info, const uint8_t* data, int len) {
  if (len == 1) {
    uint8_t val = data[0];
    Serial.print("Received: ");
    Serial.println(val);
    digitalWrite(ledPin, val ? HIGH : LOW);
  }
}

void setup() {
  Serial.begin(115200);
  pinMode(ledPin, OUTPUT);
  digitalWrite(ledPin, LOW);

  WiFi.mode(WIFI_STA);

  if (esp_now_init() != ESP_OK) {
    Serial.println("Error initializing ESP-NOW");
    return;
  }

  esp_now_register_recv_cb(onDataRecv);
}

void loop() {
  // no code needed here, all handled by callback
} r