In order to use servos, we take advantage ofpwmio. Now, in theory, you could just use the rawpwmio calls to set the frequency to 50 Hz and then set the pulse widths. But we would rather make it a little more elegant and easy!

So, instead we will useadafruit_motor which manages servos for you quite nicely!adafruit_motor is a library so be sure tograb it from the library bundle if you have not yet! If you need help installing the library, check out theCircuitPython Libraries page.

Servos come in two types: 

• Astandard hobby servo - the horn moves 180 degrees (90 degrees in each direction from zero degrees).
• Acontinuous servo - the horn moves in full rotation like a DC motor. Instead of an angle specified, you set a throttle value with 1.0 being full forward, 0.5 being half forward, 0 being stopped, and -1 being full reverse, with other values between.

Servo Wiring

The connections for a servo are the same for standard servos and continuous rotation servos.

Connect the servo'sbrownor blackground wire to ground on the CircuitPython board.

Connect the servo'sred power wire to 5V power. USB power can in some cases good for a servo or two. But some USB ports supply limited current, and operating a servo from the USB 5V line may cause a power brownout and board crash.

For more servos, you'll need an external battery pack or external power supply. Do not use 3.3V for powering a servo!

Connect the servo'syellow orwhite signal wire to the control/data pin, in this caseA1 orA2 but you can use any PWM-capable pin.

Standard Servo Code

Here's an example that will sweep a servo connected to pinA2 from 0 degrees to 180 degrees (-90 to 90 degrees) and back.

To use with CircuitPython, you need to first install a few libraries, into the lib folder on yourCIRCUITPY drive. Then you need to updatecode.py with the example script.

Thankfully, we can do this in one go.In the example below, click theDownload Project Bundle button below to download the necessary libraries and thecode.py file in a zip file. Extract the contents of the zip file, open the directoryCircuitPython_Essentials/CircuitPython_Servo/ and then click on the directory that matches the version of CircuitPython you're using and copy the contents of that directory to yourCIRCUITPY drive.

YourCIRCUITPY drive should now look similar to the following image:

# SPDX-FileCopyrightText: 2018 Kattni Rembor for Adafruit Industries## SPDX-License-Identifier: MIT"""CircuitPython Essentials Servo standard servo example"""import timeimport boardimport pwmiofrom adafruit_motor import servo# create a PWMOut object on Pin A2.pwm = pwmio.PWMOut(board.A2, duty_cycle=2 ** 15, frequency=50)# Create a servo object, my_servo.my_servo = servo.Servo(pwm)while True:    for angle in range(0, 180, 5):  # 0 - 180 degrees, 5 degrees at a time.        my_servo.angle = angle        time.sleep(0.05)    for angle in range(180, 0, -5): # 180 - 0 degrees, 5 degrees at a time.        my_servo.angle = angle        time.sleep(0.05)

# SPDX-FileCopyrightText: 2018 Kattni Rembor for Adafruit Industries## SPDX-License-Identifier: MIT"""CircuitPython Essentials Servo standard servo example"""import timeimport boardimport pwmiofrom adafruit_motor import servo# create a PWMOut object on Pin A2.pwm = pwmio.PWMOut(board.A2, duty_cycle=2 ** 15, frequency=50)# Create a servo object, my_servo.my_servo = servo.Servo(pwm)while True:    for angle in range(0, 180, 5):  # 0 - 180 degrees, 5 degrees at a time.        my_servo.angle = angle        time.sleep(0.05)    for angle in range(180, 0, -5): # 180 - 0 degrees, 5 degrees at a time.        my_servo.angle = angle        time.sleep(0.05)

Continuous Servo Code

There are two differences with Continuous Servos vs. Standard Servos:

1. Theservo object is created like my_servo = servo.ContinuousServo(pwm) instead of my_servo = servo.Servo(pwm)
2. Instead of usingmyservo.angle, you usemy_servo.throttle using a throttle value from 1.0 (full on) to 0.0 (stopped) to -1.0 (full reverse). Any number between would be a partial speed forward (positive) or reverse (negative). This is very similar to standard DC motor control with theadafruit_motor library.

This example runs full forward for 2 seconds, stops for 2 seconds, runs full reverse for 2 seconds, then stops for 4 seconds.

To use with CircuitPython, you need to first install a few libraries, into the lib folder on yourCIRCUITPY drive. Then you need to updatecode.py with the example script.

Thankfully, we can do this in one go.In the example below, click theDownload Project Bundle button below to download the necessary libraries and thecode.py file in a zip file. Extract the contents of the zip file, open the directoryCircuitPython_Essentials/CircuitPython_Continuous_Servo/ and then click on the directory that matches the version of CircuitPython you're using and copy the contents of that directory to yourCIRCUITPY drive.

YourCIRCUITPY drive should now look similar to the following image:

# SPDX-FileCopyrightText: 2019 Anne Barela for Adafruit Industries## SPDX-License-Identifier: MIT"""CircuitPython Essentials Servo continuous rotation servo example"""import timeimport boardimport pwmiofrom adafruit_motor import servo# create a PWMOut object on Pin A2.pwm = pwmio.PWMOut(board.A2, frequency=50)# Create a servo object, my_servo.my_servo = servo.ContinuousServo(pwm)while True:    print("forward")    my_servo.throttle = 1.0    time.sleep(2.0)    print("stop")    my_servo.throttle = 0.0    time.sleep(2.0)    print("reverse")    my_servo.throttle = -1.0    time.sleep(2.0)    print("stop")    my_servo.throttle = 0.0    time.sleep(4.0)

# SPDX-FileCopyrightText: 2019 Anne Barela for Adafruit Industries## SPDX-License-Identifier: MIT"""CircuitPython Essentials Servo continuous rotation servo example"""import timeimport boardimport pwmiofrom adafruit_motor import servo# create a PWMOut object on Pin A2.pwm = pwmio.PWMOut(board.A2, frequency=50)# Create a servo object, my_servo.my_servo = servo.ContinuousServo(pwm)while True:    print("forward")    my_servo.throttle = 1.0    time.sleep(2.0)    print("stop")    my_servo.throttle = 0.0    time.sleep(2.0)    print("reverse")    my_servo.throttle = -1.0    time.sleep(2.0)    print("stop")    my_servo.throttle = 0.0    time.sleep(4.0)

Pretty simple!

Note that we assume that 0 degrees is 0.5ms and 180 degrees is a pulse width of 2.5ms. That's a bit wider than the official 1-2ms pulse widths. If you have a servo that has a different range you can initialize theservo object with a differentmin_pulse andmax_pulse. For example:

my_servo = servo.Servo(pwm,min_pulse=500,max_pulse=2500) 

For more detailed information on using servos with CircuitPython, check out theCircuitPython section of the servo guide!