Bluetooth

This class provides a driver for the Bluetooth radio in the module. Currently, only basic BLE functionality is available.

Quick Usage Example

from network import Bluetooth
import time
bt = Bluetooth()
bt.start_scan(-1)

while True:
  adv = bt.get_adv()
  if adv and bt.resolve_adv_data(adv.data, Bluetooth.ADV_NAME_CMPL) == 'Heart Rate':
      try:
          conn = bt.connect(adv.mac)
          services = conn.services()
          for service in services:
              time.sleep(0.050)
              if type(service.uuid()) == bytes:
                  print('Reading chars from service = {}'.format(service.uuid()))
              else:
                  print('Reading chars from service = %x' % service.uuid())
              chars = service.characteristics()
              for char in chars:
                  if (char.properties() & Bluetooth.PROP_READ):
                      print('char {} value = {}'.format(char.uuid(), char.read()))
          conn.disconnect()
          break
      except:
          print("Error while connecting or reading from the BLE device")
          break
  else:
      time.sleep(0.050)

Bluetooth Low Energy (BLE)

Bluetooth low energy (BLE) is a subset of classic Bluetooth, designed for easy connecting and communicating between devices (in particular mobile platforms). BLE uses a methodology known as Generic Access Profile (GAP) to control connections and advertising.

GAP allows for devices to take various roles but generic flow works with devices that are either a Server (low power, resource constrained, sending small payloads of data) or a Client device (commonly a mobile device, PC or Pycom Device with large resources and processing power). Pycom devices can act as both a Client and a Server.

Constructors

class network.Bluetooth(id=0, ...)

Create a Bluetooth object, and optionally configure it. See init for params of configuration.

Example:

from network import Bluetooth
bluetooth = Bluetooth()

Methods

bluetooth.init(id=0, mode=Bluetooth.BLE, antenna=None)

  • id Only one Bluetooth peripheral available so must always be 0
  • mode currently the only supported mode is Bluetooth.BLE

  • antenna selects between the internal and the external antenna. Can be eitherBluetooth.INT_ANT, Bluetooth.EXT_ANT.

    With our development boards it defaults to using the internal antenna, but in the case of an OEM module, the antenna pin (P12) is not used, so it’s free to be used for other things.

Initialises and enables the Bluetooth radio in BLE mode.

To use an external antenna, set P12 as output pin.

Pin('P12', mode=Pin.OUT)(True)

bluetooth.deinit()

Disables the Bluetooth radio.

bluetooth.start_scan(timeout)

Starts performing a scan listening for BLE devices sending advertisements. This function always returns immediately, the scanning will be performed on the background. The return value is None. After starting the scan the function get_adv() can be used to retrieve the advertisements messages from the FIFO. The internal FIFO has space to cache 16 advertisements.

The arguments are:

  • timeout specifies the amount of time in seconds to scan for advertisements, cannot be zero. If timeout is > 0, then the BLE radio will listen for advertisements until the specified value in seconds elapses. If timeout < 0, then there’s no timeout at all, and stop_scan() needs to be called to cancel the scanning process.

Examples:

bluetooth.start_scan(10)        # starts scanning and stop after 10 seconds
bluetooth.start_scan(-1)        # starts scanning indefinitely until bluetooth.stop_scan() is called

bluetooth.stop_scan()

Stops an ongoing scanning process. Returns None.

bluetooth.isscanning()

Returns True if a Bluetooth scan is in progress. False otherwise.

bluetooth.get_adv()

Gets an named tuple with the advertisement data received during the scanning. The tuple has the following structure: (mac, addr_type, adv_type, rssi, data)

  • mac is the 6-byte ling mac address of the device that sent the advertisement.
  • addr_type is the address type. See the constants section below for more details.
  • adv_type is the advertisement type received. See the constants section below fro more details.
  • rssi is signed integer with the signal strength of the advertisement.
  • data contains the complete 31 bytes of the advertisement message. In order to parse the data and get the specific types, the method resolve_adv_data() can be used.

Example for getting mac address of an advertiser:

import ubinascii

bluetooth = Bluetooth()
bluetooth.start_scan(20) # scan for 20 seconds

adv = bluetooth.get_adv() #
ubinascii.hexlify(adv.mac) # convert hexadecimal to ascii

bluetooth.get_advertisements()

Same as the get_adv() method, but this one returns a list with all the advertisements received.

bluetooth.resolve_adv_data(data, data_type)

Parses the advertisement data and returns the requested data_type if present. If the data type is not present, the function returns None.

Arguments:

  • data is the bytes object with the complete advertisement data.
  • data_type is the data type to resolve from from the advertisement data. See constants section below for details.

Example:

import ubinascii
from network import Bluetooth
bluetooth = Bluetooth()

bluetooth.start_scan(20)
while bluetooth.isscanning():
    adv = bluetooth.get_adv()
    if adv:
        # try to get the complete name
        print(bluetooth.resolve_adv_data(adv.data, Bluetooth.ADV_NAME_CMPL))

        mfg_data = bluetooth.resolve_adv_data(adv.data, Bluetooth.ADV_MANUFACTURER_DATA)

        if mfg_data:
            # try to get the manufacturer data (Apple's iBeacon data is sent here)
            print(ubinascii.hexlify(mfg_data))

bluetooth.connect(mac_addr)

Opens a BLE connection with the device specified by the mac_addr argument. This function blocks until the connection succeeds or fails. If the connections succeeds it returns a object of type GATTCConnection.

Connections are initiated by the central device. There is a maximum of 4 simultaneous connections.

bluetooth.connect('112233eeddff') # mac address is accepted as a string

bluetooth.callback(trigger=None, handler=None, arg=None)

Creates a callback that will be executed when any of the triggers occurs. The arguments are:

  • trigger can be either Bluetooth.NEW_ADV_EVENT, Bluetooth.CLIENT_CONNECTED, or Bluetooth.CLIENT_DISCONNECTED
  • handler is the function that will be executed when the callback is triggered.
  • arg is the argument that gets passed to the callback. If nothing is given the bluetooth object itself is used.

An example of how this may be used can be seen in the bluetooth.events() method.

bluetooth.events()

Returns a value with bit flags identifying the events that have occurred since the last call. Calling this function clears the events.

Example of usage:

from network import Bluetooth

bluetooth = Bluetooth()
bluetooth.set_advertisement(name='LoPy', service_uuid=b'1234567890123456')

def conn_cb (bt_o):
    events = bt_o.events()   # this method returns the flags and clears the internal registry
    if events & Bluetooth.CLIENT_CONNECTED:
        print("Client connected")
    elif events & Bluetooth.CLIENT_DISCONNECTED:
        print("Client disconnected")

bluetooth.callback(trigger=Bluetooth.CLIENT_CONNECTED | Bluetooth.CLIENT_DISCONNECTED, handler=conn_cb)

bluetooth.advertise(True)

bluetooth.set_advertisement(* , name=None, manufacturer_data=None, service_data=None, service_uuid=None)

Configure the data to be sent while advertising. If left with the default of None the data won’t be part of the advertisement message.

The arguments are:

  • name is the string name to be shown on advertisements.
  • manufacturer_data manufacturer data to be advertised (hint: use it for iBeacons).
  • service_data service data to be advertised.
  • service_uuid uuid of the service to be advertised.

Example:

bluetooth.set_advertisement(name="advert", manufacturer_data="lopy_v1")

bluetooth.advertise([Enable])

Start or stop sending advertisements. The set_advertisement() method must have been called prior to this one.

bluetooth.service(uuid, * , isprimary=True, nbr_chars=1, start=True)

Create a new service on the internal GATT server. Returns a object of type BluetoothServerService.

The arguments are:

  • uuid is the UUID of the service. Can take an integer or a 16 byte long string or bytes object.
  • isprimary selects if the service is a primary one. Takes a bool value.
  • nbr_chars specifies the number of characteristics that the service will contain.
  • start if True the service is started immediately.
bluetooth.service('abc123')

bluetooth.disconnect_client()

Closes the BLE connection with the client.

Constants

  • Bluetooth mode: Bluetooth.BLE
  • Advertisement type: Bluetooth.CONN_ADV, Bluetooth.CONN_DIR_ADV, Bluetooth.DISC_ADV, Bluetooth.NON_CONN_ADV, Bluetooth.SCAN_RSP
  • Address type: Bluetooth.PUBLIC_ADDR, Bluetooth.RANDOM_ADDR, Bluetooth.PUBLIC_RPA_ADDR, Bluetooth.RANDOM_RPA_ADDR
  • Advertisement data type: Bluetooth.ADV_FLAG, Bluetooth.ADV_16SRV_PART, Bluetooth.ADV_T16SRV_CMPL, Bluetooth.ADV_32SRV_PART, Bluetooth.ADV_32SRV_CMPL, Bluetooth.ADV_128SRV_PART, Bluetooth.ADV_128SRV_CMPL, Bluetooth.ADV_NAME_SHORT, Bluetooth.ADV_NAME_CMPL, Bluetooth.ADV_TX_PWR, Bluetooth.ADV_DEV_CLASS, Bluetooth.ADV_SERVICE_DATA, Bluetooth.ADV_APPEARANCE, Bluetooth.ADV_ADV_INT, Bluetooth.ADV_32SERVICE_DATA, Bluetooth.ADV_128SERVICE_DATA, Bluetooth.ADV_MANUFACTURER_DATA
  • Characteristic properties (bit values that can be combined): Bluetooth.PROP_BROADCAST, Bluetooth.PROP_READ, Bluetooth.PROP_WRITE_NR, Bluetooth.PROP_WRITE, Bluetooth.PROP_NOTIFY, Bluetooth.PROP_INDICATE, Bluetooth.PROP_AUTH, Bluetooth.PROP_EXT_PROP
  • Characteristic callback events: Bluetooth.CHAR_READ_EVENT, Bluetooth.CHAR_WRITE_EVENT, Bluetooth.NEW_ADV_EVENT, Bluetooth.CLIENT_CONNECTED, Bluetooth.CLIENT_DISCONNECTED, Bluetooth.CHAR_NOTIFY_EVENT
  • Antenna type: Bluetooth.INT_ANT, Bluetooth.EXT_ANT

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