PWM

Code Example

from periphery import PWM

# Open PWM chip 0, channel 10
pwm = PWM(0, 10)

# Set frequency to 1 kHz
pwm.frequency = 1e3
# Set duty cycle to 75%
pwm.duty_cycle = 0.75

pwm.enable()

# Change duty cycle to 50%
pwm.duty_cycle = 0.50

pwm.close()

API

class periphery.PWM(chip, channel)[source]

Bases: object

Instantiate a PWM object and open the sysfs PWM corresponding to the specified chip and channel.

Parameters

  • chip (int) – PWM chip number.

  • channel (int) – PWM channel number.

Returns

PWM object.

Return type

PWM

Raises

  • PWMError – if an I/O or OS error occurs.

  • TypeError – if chip or channel types are invalid.

  • LookupError – if PWM chip does not exist.

  • TimeoutError – if waiting for PWM export times out.

PWM_STAT_RETRIES = 10
PWM_STAT_DELAY = 0.1
close()[source]

Close the PWM.

enable()[source]

Enable the PWM output.

disable()[source]

Disable the PWM output.

property devpath

Get the device path of the underlying sysfs PWM device.

Type

str

property chip

Get the PWM chip number.

Type

int

property channel

Get the PWM channel number.

Type

int

property period_ns

Get or set the PWM’s output period in nanoseconds.

Raises

  • PWMError – if an I/O or OS error occurs.

  • TypeError – if value type is not int.

Type

int

property duty_cycle_ns

Get or set the PWM’s output duty cycle in nanoseconds.

Raises

  • PWMError – if an I/O or OS error occurs.

  • TypeError – if value type is not int.

Type

int

property period

Get or set the PWM’s output period in seconds.

Raises

  • PWMError – if an I/O or OS error occurs.

  • TypeError – if value type is not int or float.

Type

int, float

property duty_cycle

Get or set the PWM’s output duty cycle as a ratio from 0.0 to 1.0.

Raises

  • PWMError – if an I/O or OS error occurs.

  • TypeError – if value type is not int or float.

  • ValueError – if value is out of bounds of 0.0 to 1.0.

Type

int, float

property frequency

Get or set the PWM’s output frequency in Hertz.

Raises

  • PWMError – if an I/O or OS error occurs.

  • TypeError – if value type is not int or float.

Type

int, float

property polarity

Get or set the PWM’s output polarity. Can be “normal” or “inversed”.

Raises

  • PWMError – if an I/O or OS error occurs.

  • TypeError – if value type is not str.

  • ValueError – if value is invalid.

Type

str

property enabled

Get or set the PWM’s output enabled state.

Raises

  • PWMError – if an I/O or OS error occurs.

  • TypeError – if value type is not bool.

Type

bool

class periphery.PWMError[source]

Bases: OSError

Base class for PWM errors.