Bluetooth Communication between Spike and MacBook

[codeadamca]

I have two LEGO Spikes. The first Spike is using Bluetooth advertising to send a string:

from pybricks.hubs import InventorHub, ThisHub
from pybricks.tools import wait

hub = InventorHub()
hub = ThisHub(broadcast_channel=39)

while True:

    print("Broadcasting...")
    hub.ble.broadcast("123456789012345678901234")

    wait(2000)

And the second Spike is listening:

from pybricks.hubs import EssentialHub, ThisHub
from pybricks.tools import wait

hub = EssentialHub()
hub = ThisHub(observe_channels=[39])

while True:

    print("Observing...")
    data = hub.ble.observe(39)

    if data is not None:
        print(data)

    wait(2000)

This is working fine!

I also have a Python script on my MacBook that is scanning Bluetooth and it is picking up the advertisements from the first Spike.

I have a second Python script running on my MacBook that is advertising. But my second Spike is not receiving it. My first Python script is also not seeing it. Here is my advertising script:

import objc
import time
from Foundation import NSObject, NSLog, NSData
from CoreBluetooth import CBCentralManager, CBPeripheralManager, CBAdvertisementDataManufacturerDataKey, CBAdvertisementDataLocalNameKey

class PeripheralDelegate(NSObject):
    def peripheralManagerDidUpdateState_(self, peripheral):
        if peripheral.state() == 5:  # 5 = Powered On
            NSLog("Peripheral is powered on, starting advertisement...")

            # Manufacturer-specific data (channel 39 = 0x0027)
            data = b'green'
            manufacturer_id = (819).to_bytes(2, 'little')  # 0x27 = 39
            adv_data = manufacturer_id + data

            adv_dict = {
                CBAdvertisementDataManufacturerDataKey: NSData.dataWithBytes_length_(adv_data, len(adv_data)),
                CBAdvertisementDataLocalNameKey: "MacColor"
            }

            peripheral.startAdvertising_(adv_dict)

peripheral_delegate = PeripheralDelegate.alloc().init()
peripheral = CBPeripheralManager.alloc().initWithDelegate_queue_options_(peripheral_delegate, None, None)

# Keep it running for 60 seconds
for _ in range(60):
    time.sleep(1)

How can I get my Spike to see advertisements from my MacBoom or other devices>?

[dlech]

                CBAdvertisementDataLocalNameKey: "MacColor"

Don't include a name. It uses manufacturer data only.

Although the CoreBluetooth docs say:

The peripheral manager only supports two keys: CBAdvertisementDataLocalNameKey and CBAdvertisementDataServiceUUIDsKey.

So this likely won't actually work.

You could add a peripheralManagerDidStartAdvertising_error_ handler to the delegate to see if it causes an error.

            manufacturer_id = (819).to_bytes(2, 'little')  # 0x27 = 39

You have to use the LEGO company ID, which is 919 (0x0397).

            data = b'green'

data needs the channel number and a header that give the type and length of the data

data = bytes([
    39,  # channel
    0,  # indicates only one value/not a tuple
    (5 << 5) | len(b"green"),  # type/length header: 5=str
    *b"green",  # str data
])

How can I get my Spike to see advertisements from my MacBoom or other devices>?

You can read more about the protocol at https://github.com/pybricks/technical-info/blob/master/pybricks-ble-broadcast-observe.md

Anything that can send the required advertisement data can work.

[codeadamca]

Thanks @dlech for the help!

I have updated my script. I can now detect my advertising using either LightBlue and nRF Connect apps, but not from the Spike. In the LightBlue app, there is no manufacturer data. I read somewhere that Mac OS strips manufacturer data from Bluetooth Low Energy advertising. Any insights on this would be very much appreciated.

My updated code can be seen here:
https://github.com/codeadamca/python-bluetooth

I'm currently using advertise4.py.

[dlech]

Any insights on this would be very much appreciated.

As I mentioned above, the official Apple docs say that only that the local name and services UUIDs are supported so I'm afraid we are out of luck making it work on macOS.