Add a buzzer driver.

src/aiy/_drivers/_buzzer.py

@@ -0,0 +1,65 @@
+# Copyright 2017 Google Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Buzzer driver."""
+
+import threading
+import time
+import RPi.GPIO as GPIO
+
+
+class Buzzer:
+    """Controls the buzzer to make some noises for a certain period.
+
+    Simple usage:
+        my_buzzer = Buzzer(channel = 22)
+        my_buzzer.buzz(30)
+    """
+
+    def __init__(self, channel):
+        GPIO.setmode(GPIO.BCM)
+        GPIO.setup(channel, GPIO.OUT)
+        self.pwm = GPIO.PWM(channel, 4000)
+        self.buzzing = False
+        self.deadline = 0
+        self.lock = threading.Lock()
+        self.exit = False
+        self.daemon = threading.Thread(target=self._daemon, daemon=True)
+        self.daemon.start()
+
+    def __del__(self):
+        with self.lock:  # pylint: disable=E1129
+            self.exit = True
+        self.pwm.stop()
+        self.daemon.Join()
+        GPIO.cleanup(self.channel)
+
+    def buzz(self, seconds):
+        with self.lock:
+            if not self.buzzing:
+                self.pwm.start(50)
+                self.buzzing = True
+                print('buzz start')
+            self.deadline = time.monotonic() + seconds
+
+    def _daemon(self):
+        while True:
+            with self.lock:  # pylint: disable=E1129
+                if self.exit:
+                    return
+                if self.buzzing and time.monotonic() > self.deadline:
+                    self.pwm.stop()
+                    self.buzzing = False
+                    print('buzz start')
+            time.sleep(1)