The file is a core header file within the official Blynk Arduino Library , specifically designed to enable communication between ESP8266-based boards (like the NodeMCU or Wemos D1 Mini) and the Blynk IoT platform. Core Functionality
, which includes all necessary dependencies for various hardware. Arduino Forum How to Install the Blynk Library The most reliable method is through the Library Manager in the Arduino IDE: Arduino Forum Open Library Manager Include Library blynksimpleesp8266 h library zip
BLYNK_WRITE(V1) int ledState = param.asInt(); digitalWrite(LED_PIN, ledState); The file is a core header file within