Merge pull request #1 from adafruit/pwm_freq

adding pwm frequency knobs

Author: siddacious

adafruit_emc2101.py

@@ -49,6 +49,8 @@
 _FAN_CONFIG = const(0x4A)
 _FAN_SPINUP = const(0x4B)
 _REG_FAN_SETTING = const(0x4C)
+_PWM_FREQ = const(0x4D)
+_PWM_DIV = const(0x4E)
 _LUT_HYSTERESIS = const(0x4F)
 
 _TEMP_FILTER = const(0xBF)
@@ -308,7 +310,10 @@ class EMC2101:  # pylint: disable=too-many-instance-attributes
     """When set to True, the magnitude of the fan output signal is inverted, making 0 the maximum
     value and 100 the minimum value"""
 
+    _fan_pwm_clock_select = RWBit(_FAN_CONFIG, 3)
     _fan_pwm_clock_override = RWBit(_FAN_CONFIG, 2)
+    _pwm_freq = RWBits(5, _PWM_FREQ, 0)
+    _pwm_freq_div = UnaryStruct(_PWM_DIV, "<B")
 
     dac_output_enabled = RWBit(_REG_CONFIG, 4)
     """When set, the fan control signal is output as a DC voltage instead of a PWM signal"""
@@ -345,7 +350,7 @@ def initialize(self):
     @property
     def internal_temperature(self):
         """The temperature as measured by the EMC2101's internal 8-bit temperature sensor"""
-        return self._int_temp  # !!! it's RAAAAAAAAARW)
+        return self._int_temp
 
     @property
     def external_temperature(self):
@@ -357,7 +362,55 @@ def external_temperature(self):
         full_tmp >>= 5
         full_tmp *= 0.125
 
-        return full_tmp  # !!! it's RAAAAAAAAARW
+        return full_tmp
+
+    def set_pwm_clock(self, use_preset=False, use_slow=False):
+        """
+        Select the PWM clock source, chosing between two preset clocks or by configuring the
+        clock using `pwm_frequency` and `pwm_frequency_divisor`.
+
+   :param bool use_preset:
+    True: Select between two preset clock sources
+    False: The PWM clock is set by `pwm_frequency` and `pwm_frequency_divisor`
+   :param bool use_slow:
+        True: Use the 1.4kHz clock
+        False: Use the 360kHz clock.
+   :type priority: integer or None
+   :return: None
+   :raises AttributeError: if use_preset is not a `bool`
+   :raises AttributeError: if use_slow is not a `bool`
+
+        """
+
+        if not isinstance(use_preset, bool):
+            raise AttributeError("use_preset must be given a bool")
+        if not isinstance(use_slow, bool):
+            raise AttributeError("use_slow_pwm must be given a bool")
+
+        self._fan_pwm_clock_override = not use_preset
+        self._fan_pwm_clock_select = use_slow
+
+    @property
+    def pwm_frequency(self):
+        """Selects the base clock frequency used for the fan PWM output"""
+        return self._pwm_freq
+
+    @pwm_frequency.setter
+    def pwm_frequency(self, value):
+        if value < 0 or value > 0x1F:
+            raise AttributeError("pwm_frequency must be from 0-31")
+        self._pwm_freq_div = value
+
+    @property
+    def pwm_frequency_divisor(self):
+        """The Divisor applied to the PWM frequency to set the final frequency"""
+        return self._pwm_freq_div
+
+    @pwm_frequency_divisor.setter
+    def pwm_frequency_divisor(self, divisor):
+        if divisor < 0 or divisor > 255:
+            raise AttributeError("pwm_frequency_divisor must be from 0-255")
+        self._pwm_freq_div = divisor
 
     @property
     def fan_speed(self):
@@ -398,30 +451,6 @@ def lut_enabled(self):
     def lut_enabled(self, enable_lut):
         self._fan_lut_prog = not enable_lut
 
-    # def get_lut(self, lut_index):
-    #     """The Look Up Table used to determine what the fan speed should be based on the measured
-    #     temperature. `lut` acts similarly to a dictionary but with restrictions:
-
-    #     * The LUT key is a temperature in celcius
-    #     * The LUT value is the corresponding fan speed in % of maximum RPM
-    #     * The LUT can only contain 8 entries. Attempting to set a ninth will
-    #         result in an `IndexError`
-
-    #     Example:
-
-    #     .. code-block:: python3
-
-    #     # If the measured external temperature goes over 20 degrees C, set the fan speed to 50%
-    #     fan_controller.lut[20] = 50
-
-    #     # If the temperature is over 30 degrees, set the fan speed to 75%
-    #     fan_controller.lut[30] = 75
-    #     """
-    #     return self._lut.__getitem__(self, lut_index)
-
-    # def set_lut(self, lut_temp, lut_speed):
-    #     self._lut.__setitem__(lut_temp, lut_speed)
-
     @property
     def lut(self):
         """The dict-like representation of the LUT"""

examples/set_pwm_freq.py

@@ -0,0 +1,26 @@
+# SPDX-FileCopyrightText: 2020 Bryan Siepert, written for Adafruit Industries
+#
+# SPDX-License-Identifier: MIT
+import time
+import board
+import busio
+from adafruit_emc2101 import EMC2101
+
+i2c = busio.I2C(board.SCL, board.SDA)
+
+emc = EMC2101(i2c)
+emc.set_pwm_clock(use_preset=False)
+# Datasheet recommends using the maximum value of 31 (0x1F)
+# to provide the highest effective resolution
+emc.pwm_frequency = 14
+
+# This divides the pwm frequency down to a smaller number
+# so larger divisor = lower frequency
+emc.pwm_frequency_divisor = 127
+
+while True:
+    print("External temperature:", emc.external_temperature, "C")
+    emc.manual_fan_speed = 50
+    time.sleep(1.5)
+    print("Fan speed:", emc.fan_speed, "RPM")
+    time.sleep(1)