using fixed PacketBuffer for ToneService

adafruit_ble_adafruit/tone_service.py

@@ -33,33 +33,62 @@
 
 import struct
 
+from _bleio import PacketBuffer
+
 from adafruit_ble.attributes import Attribute
-from adafruit_ble.characteristics import Characteristic, StructCharacteristic
+from adafruit_ble.characteristics import Characteristic, ComplexCharacteristic
 
 from .adafruit_service import AdafruitService
 
+class _TonePacket(ComplexCharacteristic):
+    uuid = AdafruitService.adafruit_service_uuid(0xC01)
+
+    format = "<HI"
+    format_size = struct.calcsize(format)
+
+    def __init__(self):
+        super().__init__(
+            properties=Characteristic.WRITE,
+            read_perm=Attribute.NO_ACCESS,
+            max_length=self.format_size,
+            fixed_length=True,
+        )
+
+    def bind(self, service):
+        """Binds the characteristic to the given Service."""
+        bound_characteristic = super().bind(service)
+        return PacketBuffer(bound_characteristic, buffer_size=1)
+
 
 class ToneService(AdafruitService):
     """Play tones."""
 
     uuid = AdafruitService.adafruit_service_uuid(0xC00)
-    tone = StructCharacteristic(
-        "<HW",
-        uuid=AdafruitService.adafruit_service_uuid(0xC01),
-        properties=Characteristic.WRITE,
-        read_perm=Attribute.NO_ACCESS,
-    )
+    _tone_packet = _TonePacket()
     """
     Tuple of (frequency: 16 bits, in Hz, duration: 32 bits, in msecs).
     If frequency == 0, a tone being played is turned off.
     if duration == 0, play indefinitely.
     """
 
+    def __init__(self, service=None):
+        super().__init__(service=service)
+        self._tone_packet_buf = bytearray(_TonePacket.format_size)
+
+    @property
+    def tone(self):
+        """Return (frequency, duration), or None if no value available"""
+        buf = self._tone_packet_buf
+        if self._tone_packet.readinto(buf) == 0:
+            # No new values available.
+            return None
+        return struct.unpack(_TonePacket.format, buf)
+
     def play(self, frequency, duration):
         """
         Frequency is in Hz. If frequency == 0, a tone being played is turned off.
         Duration is in seconds. If duration == 0, play indefinitely.
         """
-        self.tone = struct.pack(
-            "<HW", frequency, 0 if duration == 0 else int(duration * 1000 + 0.5)
+        self._tone_packet = struct.pack(
+            _TonePacket.format, frequency, 0 if duration == 0 else int(duration * 1000 + 0.5)
         )

examples/ble_adafruit_circuitplayground_bluefruit.py

@@ -34,10 +34,6 @@
 temp_last_update = 0
 
 tone_svc = ToneService()
-# Nothing playing now.
-last_tone = (0, 0)
-tone_last_freq = 0
-tone_playing = False
 
 ble = BLERadio()
 
@@ -70,8 +66,7 @@
         button_svc.set_pressed(cp.switch, cp.button_a, cp.button_b)
 
         tone = tone_svc.tone
-        if tone != last_tone:
-            print(tone)
+        if tone is not None:
             freq, duration = tone
             if freq != 0:
                 if duration != 0: