pwmio module contains classes to provide access to basic pulse IO.
All classes change hardware state and should be deinitialized when they
are no longer needed if the program continues after use. To do so, either
deinit() or use a context manager. See
Lifetime and ContextManagers for more info.
import pwmio import time from board import * pwm = pwmio.PWMOut(D13) pwm.duty_cycle = 2 ** 15 time.sleep(0.1)
This example will initialize the the device, set
duty_cycle, and then sleep 0.1 seconds.
CircuitPython will automatically turn off the PWM when it resets all
hardware after program completion. Use
deinit() or a
to do it yourself.
PWMOut(pin: microcontroller.Pin, *, duty_cycle: int = 0, frequency: int = 500, variable_frequency: bool = False)¶
Output a Pulse Width Modulated signal on a given pin.
Create a PWM object associated with the given pin. This allows you to write PWM signals out on the given pin. Frequency is fixed after init unless
variable_frequencyis True, further PWM outputs may be limited because it may take more internal resources to be flexible. So, when outputting both fixed and flexible frequency signals construct the fixed outputs first.
Simple LED fade:
import pwmio import board pwm = pwmio.PWMOut(board.D13) # output on D13 pwm.duty_cycle = 2 ** 15 # Cycles the pin with 50% duty cycle (half of 2 ** 16) at the default 500hz
PWM at specific frequency (servos and motors):
import pwmio import board pwm = pwmio.PWMOut(board.D13, frequency=50) pwm.duty_cycle = 2 ** 15 # Cycles the pin with 50% duty cycle (half of 2 ** 16) at 50hz
Variable frequency (usually tones):
import pwmio import board import time pwm = pwmio.PWMOut(board.D13, duty_cycle=2 ** 15, frequency=440, variable_frequency=True) time.sleep(0.2) pwm.frequency = 880 time.sleep(0.1)
16 bit value that dictates how much of one cycle is high (1) versus low (0). 0xffff will always be high, 0 will always be low and 0x7fff will be half high and then half low.
Depending on how PWM is implemented on a specific board, the internal representation for duty cycle might have less than 16 bits of resolution. Reading this property will return the value from the internal representation, so it may differ from the value set.
32 bit value that dictates the PWM frequency in Hertz (cycles per second). Only writeable when constructed with
Depending on how PWM is implemented on a specific board, the internal value for the PWM’s duty cycle may need to be recalculated when the frequency changes. In these cases, the duty cycle is automatically recalculated from the original duty cycle value. This should happen without any need to manually re-set the duty cycle.