Serial Communication from NodeMCU using Mongoose OS to Arduino1

// Load Mongoose OS API
load('api_timer.js');
load('api_uart.js');
load('api_sys.js');
load('api_gpio.js');
// Uart number used for this example
let uartNo = 0;
// Accumulated Rx data, will be echoed back to Tx
let rxAcc = "";
let pin=16;
GPIO.set_mode(pin, GPIO.MODE_OUTPUT);
let value = false;
 
// Configure UART at 115200 baud
UART.setConfig(uartNo, {
baudRate: 115200,
}); 
// Set dispatcher callback, it will be called whenver new Rx data or space in
// the Tx buffer becomes available
UART.setDispatcher(uartNo, function(uartNo, ud) {
  let ra = UART.readAvail(uartNo);
  if (ra > 0) {
    // Received new data: print it immediately to the console, and also
    // accumulate in the "rxAcc" variable which will be echoed back to UART later
    print("_____________________________________");
	let data = UART.read(uartNo);
	GPIO.toggle(pin);
    print("Received UART data:", data);
    rxAcc += data;
  }
}, null);
 
// Enable Rx
UART.setRxEnabled(uartNo, true);
 
// Send UART data every second
Timer.set(10000 /* milliseconds */, true /* repeat */, function() {
  print("--------_________------_________");
  value = !value;
  UART.write(
    uartNo,
    "Hello UART! "+ "\n"
  );
  rxAcc = "";
}, null);