How to use on_notification fuction to get notification

[scps990707]

I am a python beginner, I read a lot of related questions, but they all ask us to look heart_rate_collector.py , but heart_rate_collector.py did't not have any example, i really don't understand how to used it.

def on_notification(self, ble_adapter, conn_handle, uuid, data):

data should be the thing i want to get,is that right?

 

[Einar Thorsrud]

Hi,

The pc-ble-driver-py is a python wrapper for the pc-ble-driver, and the heart_rate_collector.py is the included example that demonstrate how to use it. In other words, heart_rate_collector.py is the example.

I did not understand the question other than that, though. What is it you are wondering about? As you mention on_notification, this is a function that is called whenever a notification is received, and it prints the connection handle, the UUID that got notified and the data that was notified (i.e. the received data).

[scps990707]

How do I get notification from (uuid:0xfff6) and read data.

I think "on_notification" can only show the data what i gave it(hightlight).

on_notification(self, ble_adapter, conn_handle, uuid, data)

So my question is how to get the 'data'?

I have use "self.adapter.enable_notification(new_conn, self.nus_tx)"

self.nus_tx = BLEUUID(0xfff6, self.nus_base)

[Einar Thorsrud]

Have you enabled notifications with enable_notification()? If not, you will not get any notifications, and on_notification() will never be called

[scps990707]

I want to record the notify in 0XFFF6 like image below

but now I have enable notification(),still can't received the data.

[Einar Thorsrud]

I see from the log that you find that characteristic during service discovery. Then the next is to enable notifications using enable_notification with that UUID.

[scps990707]

    def connect_and_discover(self):
        scan_duration = 5
        params = BLEGapScanParams(interval_ms=200, window_ms=150, timeout_s=scan_duration)
        message = "We are connected!\r\n"

        self.adapter.driver.ble_gap_scan_start(scan_params=params)

        try:
            new_conn = self.conn_q.get(timeout=scan_duration)
            self.adapter.service_discovery(new_conn)
            self.adapter.enable_notification(new_conn, self.nus_tx)

            return new_conn
        except Empty:
            print("No device advertising with name {TARGET_DEV_NAME} found.")
            return None

Yes ,I have enable notifications using enable_notification in the "def connect_and_discover(self):"

Is  enable_notification() return anything? or how do I know this function is working? 

[Einar Thorsrud]

Yes, it does return a status. You can see that from looking at the implementation. What is self.nus_tx? Is it the right UUID?

[scps990707]

    def __init__(self, adapter):
        super(NusCollector, self).__init__()
        self.first = 1
        self.adapter = adapter
        self.conn_q = Queue()
        self.adapter.observer_register(self)
        self.adapter.driver.observer_register(self)
        self.adapter.default_mtu = 247
        self.nus_base = BLEUUIDBase([
            0x00, 0x00, 0xff, 0xf0, 0x00 ,0x00, 0x10, 0x00, 0x80, 0x00, 0x00, 0x80, 0x5f, 0x9b, 0x34, 0xfb
        ])
        self.nus_tx = BLEUUID(0xfff6, self.nus_base)

self.nus_tx is the UUID of 0XFFF6 which is the notify one

[Einar Thorsrud]

Is the UUID Base right? In the screenshot it looks like you are using only 16 bit UUIDs, but here you are adding a base (which is probably what you should do as this is a custom service). But in any case, in order to work, this needs to match.

[scps990707]

self.nus_base = BLEUUIDBase([

0x00, 0x00, 0xff, 0xf0, 0x00 ,0x00, 0x10, 0x00, 0x80, 0x00, 0x00, 0x80, 0x5f, 0x9b, 0x34, 0xfb

])

self.nus_tx = BLEUUID(0xfff6, self.nus_base)

I think BLEUUID is to mix "0xfff6" and "self.nus_base",so self.nus_tx become[0x00, 0x00, 0xff, 0xf6, 0x00 ,0x00, 0x10, 0x00, 0x80, 0x00, 0x00, 0x80, 0x5f, 0x9b, 0x34, 0xfb]?

I also got the return form enable_notification() ,and get "None" so i think maybe my UUID is wrong

this is the UUID I want to receive data

[scps990707]

Hello is there anything I can do for it?

[Einar Thorsrud]

I don't immediately see an issue here. I suggest you take a look at this post, which includes a working script that use NUS, and enables notifications (obviously you need to change the UUID and UUID base for your custom service).