Hello Travis,
On 12 September 2016 at 16:52, Travis Griggs <travisgriggs@xxxxxxxxx> wrote:
>
>> 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!
Excellent news! Glad it helped
>>> <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.
Also good news!
> 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.
True the code I gave as an example did not update if a device was
added after initial invocation.
You will need to look at the 'InterfacesAdded' signal to see when a
device gets added.
An example of how to do that would be:
bus.add_signal_receiver(interfaces_added,
dbus_interface='org.freedesktop.DBus.ObjectManager',
signal_name='InterfacesAdded')
The interfaces_added function could then use the Device class we
created previously to connect to the PropertiesChanged signal on that
device to listen if it was connected or not.
>
> 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.
Not sure the StopNotify is a reliable way to detect that there has
been a disconnect.
The full code that I used to test what I had written above was:
#!/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 interfaces_added(path, interfaces):
if 'org.bluez.Device1' in interfaces:
print('Device added at {}'.format(path))
Device(path)
def get_iface_prop(iface, prop):
response = {}
bus = dbus.SystemBus()
mng = dbus.Interface(bus.get_object('org.bluez', '/'),
'org.freedesktop.DBus.ObjectManager')
bus.add_signal_receiver(interfaces_added,
dbus_interface='org.freedesktop.DBus.ObjectManager',
signal_name='InterfacesAdded')
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()
I removed all the devices before I started running the script so no
devices were reported at invocation. Again, I had a separate window
doing the scanning and connecting which resulted in the following
output:
$ ./connect_devices.py
Device added at /org/bluez/hci0/dev_48_C0_7B_35_98_A5
/org/bluez/hci0/dev_48_C0_7B_35_98_A5 is now 1
/org/bluez/hci0/dev_48_C0_7B_35_98_A5 is now 0
Device added at /org/bluez/hci0/dev_60_06_57_DD_4C_2F
Device added at /org/bluez/hci0/dev_54_1F_46_F1_AA_32
/org/bluez/hci0/dev_54_1F_46_F1_AA_32 is now 1
/org/bluez/hci0/dev_54_1F_46_F1_AA_32 is now 0
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