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Description
PROBLEM:
I have a peripheral that sending the notification value constantly, and no None value. But when I invoke the characterisitc.notified() method, I got an None value.
BACKGROUND:
The peripheral will send the notify event per 1 second.
During testing, the connection keeps alive.
TEST CODE:
data = await characteristic.notified() print(data) await asyncio.sleep_ms(2000) data = await characteristic.notified() print(data) data = await characteristic.notified() print(data) data = await characteristic.notified() print(data)
RESULT:
b'\n\x00' b'\x14\x00' None b'\xb\x00'
ANALYSIS:
WHY here is a None return from notified()?
The key part is on "await asyncio.sleep_ms(2000) "after first notified().
I checked the code in client.py
- When sleeping, notify events are still coming, so line 357 is still setting value to characteristc._notify_data, and line 360 is still set the notify event.
- When second notified() be invoked, in line 343, self._notify_data is not None(the data is front previous notify event), so it return immediately.
- When third notified() be invoked, line 343, self._notify_data is None (it is consumed by step 2), then it jumps to the notify_event, but because the last notify_event is set in step 1, so in line 347, it return immediately without waiting for the REAL notify event, and the return data = None.
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