Add piezo support

library/grow/__init__.py

@@ -1 +1,71 @@
 __version__ = '0.0.1'
+
+import time
+import atexit
+import threading
+import RPi.GPIO as GPIO
+
+
+class Piezo():
+    def __init__(self, gpio_pin=13):
+        GPIO.setmode(GPIO.BCM)
+        GPIO.setwarnings(False)
+        GPIO.setup(gpio_pin, GPIO.OUT, initial=GPIO.LOW)
+        self.pwm = GPIO.PWM(gpio_pin, 440)
+        self.pwm.start(0)
+        self._timeout = None
+        atexit.register(self._exit)
+
+    def frequency(self, value):
+        """Change the piezo frequency.
+
+        Loosely corresponds to musical pitch, if you suspend disbelief.
+
+        """
+        self.pwm.ChangeFrequency(value)
+
+    def start(self, frequency=None):
+        """Start the piezo.
+
+        Sets the Duty Cycle to 100%
+
+        """
+        if frequency is not None:
+            self.frequency(frequency)
+        self.pwm.ChangeDutyCycle(1)
+
+    def stop(self):
+        """Stop the piezo.
+
+        Sets the Duty Cycle to 0%
+
+        """
+        self.pwm.ChangeDutyCycle(0)
+
+    def beep(self, frequency=440, timeout=0.1, blocking=True, force=False):
+        """Beep the piezo for time seconds.
+
+        :param freq: Frequency, in hertz, of the piezo
+        :param timeout: Time, in seconds, of the piezo beep
+        :param blocking: If true, function will block until piezo has stopped
+
+        """
+        if blocking:
+            self.start(frequency=frequency)
+            time.sleep(timeout)
+            self.stop()
+            return True
+        else:
+            if self._timeout is not None:
+                if self._timeout.is_alive():
+                    if force:
+                        self._timeout.cancel()
+                    else:
+                        return False
+            self._timeout = threading.Timer(timeout, self.stop)
+            self.start(frequency=frequency)
+            self._timeout.start()
+            return True
+
+    def _exit(self):
+        self.pwm.stop()