CircuitPython PWM
Your board has pulseio support, which means you can PWM LEDs, control servos, beep piezos, and manage "pulse
train" type devices like DHT22 and Infrared.
Nearly
every pin has PWM support! For example, all ATSAMD21 board have an A0 pin which is 'true' analog out and
does not
have PWM support.
PWM with Fixed Frequency
This example will show you how to use PWM to fade the little red LED on your board.
Copy and paste the code into code.py using your favorite editor, and save the file.
Create a PWM Output
led = pulseio.PWMOut(board.D13, frequency=5000, duty_cycle=0)
Since we're using the onboard LED, we'll call the object led , use pulseio.PWMOut to create the output and pass in
the D13 LED pin to use.
Main Loop
The main loop uses range() to cycle through the loop. When the range is below 50, it PWMs the LED brightness up,
and when the range is above 50, it PWMs the brightness down. This is how it fades the LED brighter and dimmer!
The time.sleep() is needed to allow the PWM process to occur over a period of time. Otherwise it happens too quickly
for you to see!
PWM Output with Variable Frequency
Fixed frequency outputs are great for pulsing LEDs or controlling servos. But if you want to make some beeps with a
piezo, you'll need to vary the frequency.
The following example uses pulseio to make a series of tones on a piezo.
To use with any of the M0 boards, no changes to the following code are needed.
import time
import board
import pulseio
led = pulseio.PWMOut(board.D13, frequency=5000, duty_cycle=0)
while True:
for i in range(100):
# PWM LED up and down
if i < 50:
led.duty_cycle = int(i * 2 * 65535 / 100) # Up
else:
led.duty_cycle = 65535 - int((i - 50) * 2 * 65535 / 100) # Down
time.sleep(0.01)
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