> On Sep 7, 2016, at 3:19 PM, Barry Byford <31baz66@xxxxxxxxx> wrote:
>
> Hi Travis,
>
> On 7 September 2016 at 22:14, Travis Griggs <travisgriggs@xxxxxxxxx> wrote:
> <snip>
>> What is the difference between and adapter and device in the lingo here?
> As you correctly identify the adapter is the bluetooth dongle on your Linux SBC
> The device is the remote Bluetooth device that you are connecting to.
Aha! Lightbulb moment there for me. Thank you so much!
>
>> <reboot linux device>
>> # ./connected
>> (no output)
>> <ble connect from iphone>
>> # ./connected
>> /org/bluez/hci0/dev_49_7C_73_51_21_1E Connected: 1
>> <terminate iOS app, should disconnect>
>> # ./connected
>> /org/bluez/hci0/dev_49_7C_73_51_21_1E Connected: 0
>> <wait a minute or so>
>> # ./connected
>> /org/bluez/hci0/dev_49_7C_73_51_21_1E Connected: 0
>> <reconnect iOs app>
>> ./connected
>> /org/bluez/hci0/dev_49_7C_73_51_21_1E Connected: 0
>> /org/bluez/hci0/dev_41_7B_77_4F_E4_AA Connected: 1
>> <disconnect>
>
> If looks like your iOS app is creating a different device address each
> time it is started. I see this on a few of the Android apps that I use
> that emulate things like heart rate monitors or battery services.
>
>
>> Is there a way to register something more event based so I could be notified when it changes?
>
> Yes there is. You can connect to the 'PropertiesChanged' signal on the
> 'org.bluez.Device1' interface.
> I've done a piece of code that demonstrates this. I've used an Android
> app to test it. To get around the issue of it having a different
> address each time I switch the app on, I've left the app running and
> then in a separate window on my SBC I use Bluetoothctl to do the
> connect/disconnect commands.
>
> Hopefully the email tool will not mangle the formatting of this code too much:
>
> #!/usr/bin/env python3
> import dbus
> import dbus.mainloop.glib
> from gi.repository import GLib
>
> dbus.mainloop.glib.DBusGMainLoop(set_as_default=True)
> mainloop = GLib.MainLoop()
>
>
> def get_iface_prop(iface, prop):
> response = {}
> bus = dbus.SystemBus()
> mng = dbus.Interface(bus.get_object('org.bluez', '/'),
> 'org.freedesktop.DBus.ObjectManager')
> for path, ifaces in mng.GetManagedObjects().items():
> if iface in ifaces:
> response[path] = ifaces[iface][prop]
> return response
>
> class Device:
> def __init__(self, device_path):
> self.bus = dbus.SystemBus()
> self.device_path = device_path
> self.device_obj = self.bus.get_object('org.bluez', device_path)
> device_props = dbus.Interface(self.device_obj, dbus.PROPERTIES_IFACE)
> device_props.connect_to_signal('PropertiesChanged',
> self.on_prop_changed)
>
> def on_prop_changed(self, iface, changed_props, invalidated_props):
> if 'org.bluez.Device1' in iface:
> if 'Connected' in changed_props:
> print('{0} is now {1}'.format(self.device_path,
> changed_props['Connected']))
>
>
> if __name__ == '__main__':
> for k, v in get_iface_prop('org.bluez.Device1', 'Connected').items():
> print('{0} is {1}'.format(k, v))
> Device(k)
>
> mainloop.run()
>
> My test output looked like this:
>
> ./connected_devices.py
> /org/bluez/hci0/dev_E8_A9_41_CE_31_5A is 0
> /org/bluez/hci0/dev_5E_4B_97_7B_22_C3 is 1
> /org/bluez/hci0/dev_B0_B4_48_BE_5D_83 is 0
> /org/bluez/hci0/dev_F7_17_E4_09_C0_C6 is 0
> /org/bluez/hci0/dev_8C_2D_AA_44_0E_3A is 0
> /org/bluez/hci0/dev_5E_4B_97_7B_22_C3 is now 0
> /org/bluez/hci0/dev_5E_4B_97_7B_22_C3 is now 1
> /org/bluez/hci0/dev_5E_4B_97_7B_22_C3 is now 0
>
> This was all done using BlueZ 5.40 with the experimental flag switched
> on. I hope that helps move things forward for you.
Your code worked. But it seems that it only has a one a time pass to determine which remote devices to register the property change. So for a given snapshot of current devices, it can notify their state changes. But it won’t notice if a new object path shows up.
It seems to me though, that maybe I’m going about this wrong. I don’t care about the device identity, or which devices are connected or not. What I really care about is if any device is connected to my app. And maybe I have this (kind of indirectly). My characteristic will get a StartNotify/StopNotify event on connect/disconnect edges. I can just use those to keep track of when I’m active or not.
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