Servo sweep

What this example shows

Driving a hobby servo by angle instead of raw ticks, and sweeping it back and forth across its configured range. This is the board's primary advertised use case.

The example code

from pca9685 import PCA9685
from utime import sleep_ms

pwm = PCA9685()  # sets 50Hz PWM frequency by default, suitable for hobby servos

# Adjust to match your servo's datasheet if it doesn't reach full range
pwm.setServoPulseRange(500, 2500)  # microseconds
pwm.setServoAngleRange(0, 180)  # degrees

while True:
    for angle in range(0, 181):
        pwm.setServoAngle(0, angle)
        sleep_ms(15)

    for angle in range(180, -1, -1):
        pwm.setServoAngle(0, angle)
        sleep_ms(15)

Expected result:

No serial output. A hobby servo connected to channel 0 sweeps from 0 to 180 degrees and back, each direction taking a little under 3 seconds, then repeats.

Functions used

PCA9685(i2c=None, address=PCA9685_DEFAULT_ADDRESS)returns None

Constructor. Sets the default 50 Hz PWM frequency, which is what hobby servos expect. If i2c is not supplied, it auto-detects the I2C pins on ESP32, ESP8266 and Soldered Dasduino CONNECTPLUS boards.

ReturnsConstructor; no return value.

Parameters

Type	Name	Description
I2C	i2c	Initialized machine.I2C object. Optional; auto-detected on known boards.
int	address	I2C address of the board. Defaults to PCA9685_DEFAULT_ADDRESS (0x40).

setServoPulseRange(minPulseUs, maxPulseUs)returns None

Configures the pulse width, in microseconds, that setServoAngle() maps to the minimum and maximum angle. Match this to your servo's own datasheet if it does not reach its full mechanical range at the library's default.

ReturnsNothing.

Parameters

Type	Name	Description
int	minPulseUs	Pulse width in microseconds mapped to the minimum angle. Library default: 500 us.
int	maxPulseUs	Pulse width in microseconds mapped to the maximum angle. Library default: 2500 us.

setServoAngleRange(minAngle, maxAngle)returns None

Configures the angle range, in degrees, accepted by setServoAngle().

ReturnsNothing.

Parameters

Type	Name	Description
float	minAngle	Angle in degrees mapped to minPulseUs. Library default: 0.
float	maxAngle	Angle in degrees mapped to maxPulseUs. Library default: 180.

setServoAngle(channel, angle)returns bool

Drives a hobby servo on the given channel to an angle, clamped to the configured angle range. Internally converts the angle to a pulse width and calls setPWM() for you. Assumes the default 50 Hz frequency set by the constructor.

ReturnsTrue on success, False if channel is out of range.

Parameters

Type	Name	Description
int	channel	Channel number, 0 to 15.
float	angle	Angle in degrees, clamped to the range set by setServoAngleRange().

Putting it together

setServoPulseRange() and setServoAngleRange() are one-time setup calls: run them once, before the first setServoAngle(). After that, setServoAngle() does the angle-to-pulse-width math and calls setPWM() for you, so you never need to compute tick counts by hand for a servo.

This example relies on the constructor's default 50 Hz frequency, which is what hobby servos expect. If something else on the same board has since called setPWMFreq() to a different value, for example for an LED on another channel, keep servo channels at 50 Hz rather than relying on setServoAngle() at a different frequency.

SourceOpen the verified MicroPython exampleView the exact source used by this page.Examples/pca9685-servoSweep.py