Adafruit Blinka supports PWMOut! This means you can easily pulse LEDs and control servos from your Raspberry Pi using any GPIO pin! This page will walk you through wiring up an LED and a servo, and provide an example for each.
Update Adafruit Blinka
Before getting started, make sure you're running the latest version of Adafruit Blinka. If you have not already installed it, run the following:
pip3 install adafruit-blinka
If you've previously installed it, you should run a pip3 update:
pip3 install --upgrade adafruit-blinka
Once you're certain that you are running the latest version of Adafruit Blinka, you can continue!
Supported Pins
PWMOut is supported on all GPIO pins on the Raspberry Pi! They are independent, and each can have a different frequency and duty cycle.
PWM - LEDs
This example will show you how to use PWM to pulse fade an LED.
First, wire up the LED to the Raspberry Pi.
Double-check you have the right wires connected to the right location, it can be tough to keep track of pins as there are forty of them!
No additional libraries are needed, so we can go straight on to the example code.
Run the following code:
# SPDX-FileCopyrightText: 2018 Kattni Rembor for Adafruit Industries
#
# SPDX-License-Identifier: MIT
import time
import board
import pwmio
led = pwmio.PWMOut(board.D5, 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)
Verify that the LED is pulsing. If not, check that it's wired to GPIO #5, the resistor is installed correctly, and you have a ground wire to the Raspberry Pi.
Type control-C to quit.
Servo Control
In order to use servos, we take advantage of pulseio. You have two options. You can use the raw pulseio calls to set the frequency to 50 Hz and then set the pulse widths. Or, you can use adafruit_motor which manages servos for you quite nicely.
This section will cover both options.
Install adafruit_motor by running pip3 install adafruit-circuitpython-motor
First, wire up a servo to your Raspberry Pi:
- Servo power (red wire) to Raspberry Pi 5V
- Servo ground (black/brown wire) to Raspberry Pi ground
- Servo signal (yellow/white wire) to Raspberry Pi GPIO5
# SPDX-FileCopyrightText: 2020 Kattni Rembor for Adafruit Industries
#
# SPDX-License-Identifier: MIT
import time
import board
import pwmio
# Initialize PWM output for the servo (on pin D5):
servo = pwmio.PWMOut(board.D5, frequency=50)
# Create a function to simplify setting PWM duty cycle for the servo:
def servo_duty_cycle(pulse_ms, frequency=50):
period_ms = 1.0 / frequency * 1000.0
duty_cycle = int(pulse_ms / (period_ms / 65535.0))
return duty_cycle
# Main loop will run forever moving between 1.0 and 2.0 mS long pulses:
while True:
servo.duty_cycle = servo_duty_cycle(1.0)
time.sleep(1.0)
servo.duty_cycle = servo_duty_cycle(2.0)
time.sleep(1.0)
The servo should sweep back and forth repeatedly. If it does not, verify your wiring matches the diagram above.
Type control-C to quit.
# SPDX-FileCopyrightText: 2018 Kattni Rembor for Adafruit Industries
#
# SPDX-License-Identifier: MIT
import time
import board
import pwmio
from adafruit_motor import servo
# create a PWMOut object on Pin D5.
pwm = pwmio.PWMOut(board.D5, duty_cycle=2 ** 15, frequency=50)
# Create a servo object.
servo = servo.Servo(pwm)
while True:
for angle in range(0, 180, 5): # 0 - 180 degrees, 5 degrees at a time.
servo.angle = angle
time.sleep(0.05)
for angle in range(180, 0, -5): # 180 - 0 degrees, 5 degrees at a time.
servo.angle = angle
time.sleep(0.05)
The servo should sweep back and forth in steps. If it does not, verify your wiring matches the diagram above.
Type control-C to quit.
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