text: import uos
  import machine
  import utime
  from machine import Pin
  
  rel1 - Pin(3, Pin.OUT)
  rel3 - Pin(4, Pin.OUT)
  rel3 - Pin(5, Pin.OUT)
  rel4 - Pin(6, Pin.OUT)
  
  uart0 = machine.UART(0,baudrate=9600)
  
  def clartBuf(uart=uart0):
      print("Clear UART buffer "+ str(uart))
      while uart.any():
          print(uart.read(1))
  
  clartBuf()
  
  prvMills = utime.ticks_ms()
  bUart0 = b''
  while (1):
      if uart0.any():
          b0 = uart0.read(1)
          bUart0 = bUart0 + b0
          if b0.decode('utf-8') == 'A':
              rel1.toggle()
          if b0.decode('utf-8') == 'B':
              rel2.toggle()
          if b0.decode('utf-8') == 'C':
              rel3.toggle()
          if b0.decode('utf-8') == 'D':
              rel4.toggle()
  