Reading a bluetooth characteristic value on an Iphone

  • I am trying to read the characteristic value from the LoPy on an Iphone with the example code from the Pycom documentation.

    from network import Bluetooth

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

    def conn_cb (bt_o):
    events =
    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)


    srv1 = bluetooth.service(uuid=b'1234567890123456', isprimary=True)

    chr1 = srv1.characteristic(uuid=b'ab34567890123456', value=5)

    char1_read_counter = 0
    def char1_cb_handler(chr):
    global char1_read_counter
    char1_read_counter += 1

    events =
    if  events & Bluetooth.CHAR_WRITE_EVENT:
        print("Write request with value = {}".format(chr.value()))
        if char1_read_counter < 3:
            print('Read request on char 1')
            return 'ABC DEF'

    char1_cb = chr1.callback(trigger=Bluetooth.CHAR_WRITE_EVENT | Bluetooth.CHAR_READ_EVENT, handler=char1_cb_handler)

    I can get the phone to connect to the LoPy and receive the characteristic data from it. However, I cannot figure out how to read the data to get the characteristic's value of 5. I am using Xcode with the Swift programming language and its Core Bluetooth framework. When reading a value on the LoPy, there is a simply a read() function. How does this function work and is there a way to get the code behind it, so I could set up a similar implementation in Swift?

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