text: # Test GATTC/S data transfer between peripheral and central, and use of gatts_set_buffer()
  
  from micropython import const
  import time, machine, bluetooth
  
  TIMEOUT_MS = 5000
  
  _IRQ_CENTRAL_CONNECT = const(1 << 0)
  _IRQ_CENTRAL_DISCONNECT = const(1 << 1)
  _IRQ_GATTS_WRITE = const(1 << 2)
  _IRQ_PERIPHERAL_CONNECT = const(1 << 6)
  _IRQ_PERIPHERAL_DISCONNECT = const(1 << 7)
  _IRQ_GATTC_SERVICE_RESULT = const(1 << 8)
  _IRQ_GATTC_CHARACTERISTIC_RESULT = const(1 << 9)
  _IRQ_GATTC_READ_RESULT = const(1 << 11)
  _IRQ_GATTC_WRITE_STATUS = const(1 << 12)
  _IRQ_GATTC_NOTIFY = const(1 << 13)
  
  SERVICE_UUID = bluetooth.UUID("00000001-1111-2222-3333-444444444444")
  CHAR_CTRL_UUID = bluetooth.UUID("00000002-1111-2222-3333-444444444444")
  CHAR_RX_UUID = bluetooth.UUID("00000003-1111-2222-3333-444444444444")
  CHAR_TX_UUID = bluetooth.UUID("00000004-1111-2222-3333-444444444444")
  CHAR_CTRL = (CHAR_CTRL_UUID, bluetooth.FLAG_WRITE | bluetooth.FLAG_NOTIFY)
  CHAR_RX = (CHAR_RX_UUID, bluetooth.FLAG_WRITE | bluetooth.FLAG_WRITE_NO_RESPONSE)
  CHAR_TX = (CHAR_TX_UUID, bluetooth.FLAG_NOTIFY)
  SERVICE = (SERVICE_UUID, (CHAR_CTRL, CHAR_RX, CHAR_TX))
  SERVICES = (SERVICE,)
  
  last_event = None
  last_data = None
  ctrl_value_handle = 0
  rx_value_handle = 0
  tx_value_handle = 0
  
  
  def irq(event, data):
      global last_event, last_data, ctrl_value_handle, rx_value_handle, tx_value_handle
      last_event = event
      last_data = data
      if event == _IRQ_CENTRAL_CONNECT:
          print("_IRQ_CENTRAL_CONNECT")
      elif event == _IRQ_CENTRAL_DISCONNECT:
          print("_IRQ_CENTRAL_DISCONNECT")
      elif event == _IRQ_GATTS_WRITE:
          print("_IRQ_GATTS_WRITE")
      elif event == _IRQ_PERIPHERAL_CONNECT:
          print("_IRQ_PERIPHERAL_CONNECT")
      elif event == _IRQ_PERIPHERAL_DISCONNECT:
          print("_IRQ_PERIPHERAL_DISCONNECT")
      elif event == _IRQ_GATTC_CHARACTERISTIC_RESULT:
          if data[-1] == CHAR_CTRL_UUID:
              print("_IRQ_GATTC_SERVICE_RESULT", data[-1])
              ctrl_value_handle = data[2]
          elif data[-1] == CHAR_RX_UUID:
              print("_IRQ_GATTC_SERVICE_RESULT", data[-1])
              rx_value_handle = data[2]
          elif data[-1] == CHAR_TX_UUID:
              print("_IRQ_GATTC_SERVICE_RESULT", data[-1])
              tx_value_handle = data[2]
      elif event == _IRQ_GATTC_READ_RESULT:
          print("_IRQ_GATTC_READ_RESULT", data[-1])
      elif event == _IRQ_GATTC_WRITE_STATUS:
          print("_IRQ_GATTC_WRITE_STATUS", data[-1])
      elif event == _IRQ_GATTC_NOTIFY:
          print("_IRQ_GATTC_NOTIFY", data[-1])
  
  
  def wait_for_event(event, timeout_ms):
      t0 = time.ticks_ms()
      while time.ticks_diff(time.ticks_ms(), t0) < timeout_ms:
          if isinstance(event, int):
              if last_event == event:
                  break
          elif event():
              break
          machine.idle()
  
  
  # Acting in peripheral role.
  def instance0():
      multitest.globals(BDADDR=ble.config("mac"))
      ((char_ctrl_handle, char_rx_handle, char_tx_handle),) = ble.gatts_register_services(SERVICES)
  
      # Increase the size of the rx buffer and enable append mode.
      ble.gatts_set_buffer(char_rx_handle, 100, True)
  
      print("gap_advertise")
      ble.gap_advertise(20_000, b"\x02\x01\x06\x04\xffMPY")
      multitest.next()
      try:
          # Wait for central to connect to us.
          wait_for_event(_IRQ_CENTRAL_CONNECT, TIMEOUT_MS)
          if last_event != _IRQ_CENTRAL_CONNECT:
              return
          conn_handle, _, _ = last_data
  
          # Wait for the central to signal that it's done with its part of the test.
          wait_for_event(
              lambda: last_event == _IRQ_GATTS_WRITE and last_data[1] == char_ctrl_handle,
              2 * TIMEOUT_MS,
          )
  
          # Read all accumulated data from the central.
          print("gatts_read:", ble.gatts_read(char_rx_handle))
  
          # Notify the central a few times.
          for i in range(4):
              time.sleep_ms(300)
              ble.gatts_notify(conn_handle, char_tx_handle, "message{}".format(i))
  
          # Notify the central that we are done with our part of the test.
          time.sleep_ms(300)
          ble.gatts_notify(conn_handle, char_ctrl_handle, "OK")
  
          # Wait for the central to disconnect.
          wait_for_event(_IRQ_CENTRAL_DISCONNECT, TIMEOUT_MS)
      finally:
          ble.active(0)
  
  
  # Acting in central role.
  def instance1():
      multitest.next()
      try:
          # Connect to peripheral and then disconnect.
          print("gap_connect")
          ble.gap_connect(0, BDADDR)
          wait_for_event(_IRQ_PERIPHERAL_CONNECT, TIMEOUT_MS)
          if last_event != _IRQ_PERIPHERAL_CONNECT:
              return
          conn_handle, _, _ = last_data
  
          # Discover characteristics.
          ble.gattc_discover_characteristics(conn_handle, 1, 65535)
          wait_for_event(
              lambda: ctrl_value_handle and rx_value_handle and tx_value_handle, TIMEOUT_MS
          )
  
          # Write to the characteristic a few times, with and without response.
          for i in range(4):
              print("gattc_write")
              ble.gattc_write(conn_handle, rx_value_handle, "central{}".format(i), i & 1)
              if i & 1:
                  wait_for_event(_IRQ_GATTC_WRITE_STATUS, TIMEOUT_MS)
              time.sleep_ms(400)
  
          # Write to say that we are done with our part of the test.
          ble.gattc_write(conn_handle, ctrl_value_handle, "OK", 1)
          wait_for_event(_IRQ_GATTC_WRITE_STATUS, TIMEOUT_MS)
  
          # Wait for notification that peripheral is done with its part of the test.
          wait_for_event(
              lambda: last_event == _IRQ_GATTC_NOTIFY and last_data[1] == ctrl_value_handle,
              TIMEOUT_MS,
          )
  
          # Disconnect from peripheral.
          print("gap_disconnect:", ble.gap_disconnect(conn_handle))
          wait_for_event(_IRQ_PERIPHERAL_DISCONNECT, TIMEOUT_MS)
      finally:
          ble.active(0)
  
  
  ble = bluetooth.BLE()
  ble.active(1)
  ble.irq(irq)
  