text: # SPDX-FileCopyrightText: 2021 ladyada for Adafruit Industries
  # SPDX-License-Identifier: MIT
  
  # Example to send a packet periodically between addressed nodes with ACK
  # Author: Jerry Needell
  #
  import time
  import board
  import busio
  import digitalio
  import adafruit_rfm9x
  
  # set the time interval (seconds) for sending packets
  transmit_interval = 10
  
  # Define radio parameters.
  RADIO_FREQ_MHZ = 915.0  # Frequency of the radio in Mhz. Must match your
  # module! Can be a value like 915.0, 433.0, etc.
  
  # Define pins connected to the chip.
  # set GPIO pins as necessary -- this example is for Raspberry Pi
  CS = digitalio.DigitalInOut(board.CE1)
  RESET = digitalio.DigitalInOut(board.D25)
  
  # Initialize SPI bus.
  spi = busio.SPI(board.SCK, MOSI=board.MOSI, MISO=board.MISO)
  # Initialze RFM radio
  rfm9x = adafruit_rfm9x.RFM9x(spi, CS, RESET, RADIO_FREQ_MHZ)
  
  # set delay before sending ACK
  rfm9x.ack_delay = 0.1
  # set node addresses
  rfm9x.node = 1
  rfm9x.destination = 2
  # initialize counter
  counter = 0
  ack_failed_counter = 0
  # send startup message from my_node
  rfm9x.send_with_ack(bytes("startup message from node {}".format(rfm9x.node), "UTF-8"))
  
  # Wait to receive packets.
  print("Waiting for packets...")
  # initialize flag and timer
  time_now = time.monotonic()
  while True:
      # Look for a new packet: only accept if addresses to my_node
      packet = rfm9x.receive(with_ack=True, with_header=True)
      # If no packet was received during the timeout then None is returned.
      if packet is not None:
          # Received a packet!
          # Print out the raw bytes of the packet:
          print("Received (raw header):", [hex(x) for x in packet[0:4]])
          print("Received (raw payload): {0}".format(packet[4:]))
          print("RSSI: {0}".format(rfm9x.last_rssi))
          # send reading after any packet received
      if time.monotonic() - time_now > transmit_interval:
          # reset timeer
          time_now = time.monotonic()
          counter += 1
          # send a  mesage to destination_node from my_node
          if not rfm9x.send_with_ack(
              bytes("message from node node {} {}".format(rfm9x.node, counter), "UTF-8")
          ):
              ack_failed_counter += 1
              print(" No Ack: ", counter, ack_failed_counter)
  