Function for gets the pwm frequency

pca9685_driver/device.py

@@ -188,3 +188,15 @@ def set_pwm_frequency(self, value):
         self.sleep()
         self.write(Registers.PRE_SCALE, reg_val)
         self.wake()
+
+    def calc_frequency(self, prescale):
+        """Calculate the frequency by the controller's prescale, specified by the PCA9685 datasheet
+
+        :param prescale: the prescale value of the controller
+        """
+        return int(round(self.__oscillator_clock / ((prescale + 1) * 4096.0)))
+
+    def get_pwm_frequency(self):
+        """Gets the frequency for all PWM output"""
+
+        return self.calc_frequency(self.read(Registers.PRE_SCALE))

test/test_device.py

@@ -74,3 +74,21 @@ def test_set_pwm_value(self):
         # Assert
         self.assertEqual(dev.bus.values[24], 18)
         self.assertEqual(dev.bus.values[25], 4)
+
+    def test_calc_frequency(self):
+        # Arrange
+        dev = Device(0, 0, FakeSMBus)
+
+        # Act & Assert
+        self.assertEqual(dev.calc_frequency(30), 197)
+        self.assertEqual(dev.calc_frequency(5), 1017)
+
+    def test_get_pwm_frequency(self):
+        # Arrange
+        dev = Device(0, 0, FakeSMBus)
+
+        # Act
+        dev.set_pwm_frequency(197)
+
+        # Assert
+        self.assertEqual(dev.get_pwm_frequency(), 197)