use notify properly for pixel and sound services

Author: dhalbert

adafruit_ble_adafruit/addressable_pixel_service.py

@@ -69,15 +69,18 @@ class _PixelPacket(ComplexCharacteristic):
 
     uuid = AdafruitService.adafruit_service_uuid(0x903)
 
-    def __init__(self, length):
+    def __init__(self):
         super().__init__(
             properties=Characteristic.WRITE,
             read_perm=Attribute.NO_ACCESS,
-            max_length=length,
+            # max length will be set on binding.
         )
 
     def bind(self, service):
         """Binds the characteristic to the given Service."""
+        # Set Characteristic's max length, based on value from AddressablePixelService.
+        # + 3 is for size of start and flags
+        self.max_length = service.data_length + 3
         bound_characteristic = super().bind(service)
         return _bleio.PacketBuffer(bound_characteristic, buffer_size=1)
 
@@ -100,13 +103,14 @@ class AddressablePixelService(AdafruitService):
     0 = WS2812 (NeoPixel), 800kHz
     1 = SPI (APA102: DotStar)
     """
+    _pixel_packet = _PixelPacket()
+    """Pixel-setting data. max_length is supplied on binding."""
 
-    def __init__(self, length, service=None):
-        # Delay creation of _pixel_packet until length is given.
-        self.__class__._pixel_packet = _PixelPacket(length + 3)
-        super().__init__(service=service)
+    def __init__(self, data_length, service=None):
+        # Used by _PixelPacket when binding is done.
+        self.data_length = data_length
         self._pixel_packet_buf = None
-        self._buf_length = length
+        super().__init__(service=service)
 
     @property
     def values(self):

adafruit_ble_adafruit/microphone_service.py

@@ -37,11 +37,31 @@
 from adafruit_ble_adafruit.adafruit_service import AdafruitService
 
 
+class _SoundSamples(Characteristic):  # pylint: disable=too-few-public-methods
+    """The Characteristic's max_length is passed from the service,
+    so defer setting it until binding happens.
+    """
+
+    def __init__(self):
+        super().__init__(
+            uuid=AdafruitService.adafruit_service_uuid(0xB01),
+            properties=(Characteristic.READ | Characteristic.NOTIFY),
+            write_perm=Attribute.NO_ACCESS,
+        )
+
+    def __bind_locally(self, service, initial_value):
+        # The service instantiation determines how many samples
+        # to send.
+        self.max_length = service.num_samples * 2
+        return super().__bind_locally(service, initial_value)
+
+
 class MicrophoneService(AdafruitService):  # pylint: disable=too-few-public-methods
     """Digital microphone data."""
 
     uuid = AdafruitService.adafruit_service_uuid(0xB00)
-    sound_samples = None
+
+    sound_samples = _SoundSamples()
     """
     Array of 16-bit sound samples, varying based on period.
     If num_channel == 2, the samples alternate left and right channels.
@@ -57,11 +77,7 @@ class MicrophoneService(AdafruitService):  # pylint: disable=too-few-public-meth
     measurement_period = AdafruitService.measurement_period_charac()
     """Initially 1000ms."""
 
-    def __init__(self, max_samples, service=None):
-        self.__class__.sound_samples = Characteristic(
-            uuid=AdafruitService.adafruit_service_uuid(0xB01),
-            properties=(Characteristic.READ | Characteristic.NOTIFY),
-            write_perm=Attribute.NO_ACCESS,
-            max_length=max_samples * 2,
-        )
+    def __init__(self, num_samples, service=None):
+        # Used by _SoundSamples when binding is done.
+        self.num_samples = num_samples
         super().__init__(service=service)

examples/ble_adafruit_circuitplayground_bluefruit.py

@@ -25,7 +25,8 @@
 accel_svc.measurement_period = 100
 accel_last_update = 0
 
-NEOPIXEL_BUF_LENGTH = const(30)
+# 3 RGB bytes * 10 pixels.
+NEOPIXEL_BUF_LENGTH = const(3 * 10)
 neopixel_svc = AddressablePixelService(NEOPIXEL_BUF_LENGTH)
 neopixel_buf = bytearray(NEOPIXEL_BUF_LENGTH)
 # Take over NeoPixel control from cp.

examples/ble_adafruit_clue_bluefruit.py renamed to examples/ble_adafruit_clue.py

@@ -29,7 +29,7 @@
 accel_svc.measurement_period = 100
 accel_last_update = 0
 
-# CLUE has just one board pixel. The 3 is for RGB.
+# CLUE has just one board pixel. 3 RGB bytes * 1 pixel.
 NEOPIXEL_BUF_LENGTH = const(3 * 1)
 neopixel_svc = AddressablePixelService(NEOPIXEL_BUF_LENGTH)
 neopixel_buf = bytearray(NEOPIXEL_BUF_LENGTH)
@@ -106,6 +106,8 @@
             clue._mic.record(  # pylint: disable=protected-access
                 mic_samples, len(mic_samples)
             )
+            # This subtraction yields unsigned values which are
+            # reinterpreted as signed after passing.
             mic_svc.sound_samples = mic_samples - 32768
             mic_last_update = now_msecs