Scale fan setting to match PWM_F
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This was previously fixed in adafruit#4, but it looks like the fix got clobbered when the LUT code was split out to a separate file.
This conversion is going to depend on the PWM_F and DAC register values, so it needs to be a method. Use this method in `manual_fan_speed()` as well as the LUT subclass. Move the `_pwm_freq` register definition into the base class too. It will be needed for the fixed fan speed conversions. Also import the `MAX_LUT_*` constants from the base module rather than redefining them.
- Add a `_full_speed_lsb` member variable which represents the (smallest) LSB value corresponding to a 100% fan setting. - Add a `_calculate_full_speed()` method that computes it. - Use `_full_speed_lsb` when converting percentages to fan speed settings and back. Fixes adafruit#19.
Recalculate the full speed LSB setting when this property is changed too.
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thanks! hopefully someone from the circuitpy community could test this PR and then we will merge |
FoamyGuy
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Jan 10, 2022
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Updating https://github.com/adafruit/Adafruit_CircuitPython_DPS310 to 2.1.0 from 2.0.0: > Merge pull request adafruit/Adafruit_CircuitPython_DPS310#20 from FoamyGuy/default_import Updating https://github.com/adafruit/Adafruit_CircuitPython_EMC2101 to 1.1.10 from 1.1.9: > Merge pull request adafruit/Adafruit_CircuitPython_EMC2101#20 from stoklund/full_speed > update rtd py version Updating https://github.com/adafruit/Adafruit_CircuitPython_HT16K33 to 4.1.9 from 4.1.8: > Merge pull request adafruit/Adafruit_CircuitPython_HT16K33#95 from tekktrik/doc/update-documentation
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When converting a fan speed percentage to an LSB byte written to the EMC2101 controller, the conversion should translate 100% to 2*PWM_F because the chip determines the PWM duty cycle that way.
The changes in this PR calculate and cache the byte value to use for 100% fan speed in the function
_calculate_full_speed(). This cached full speed value is recomputed wheneveremc.pwm_frequencyoremc.dac_output_enabledare changed — these are the two registers affecting the value.When setting
emc.manual_fan_speedor one of the LUT values, the cached full speed value is used to compute the byte to be programmed into the chip. This means thatemc.pwm_frequencyshould always be set before programming the LUT or manual speed setting.My new oscilloscope arrived today (yay!), so I was able to test this code by measuring the duty cycle on the FAN pin. I tested 10% fan speed increments both with the default PWM frequency, and with
PWM_F=5which produces a 35 kHz PWM signal.Both PWM frequencies plot as a straight line. At 35 kHz, I measured a duty cycle about 0.75% less that the programmed value. I think this is caused by the 1 µs rise time on the open drain FAN pin.