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)