Boris Lovosevic edited this page Jan 30, 2018 · 19 revisions

machine Module

Class PWM


This class includes PWM support using ESP32 LEDC peripheral


Features

  • up to 8 pwm channels can be used
  • 4 pwm timers are available, multiple channels can use the same timer
  • all pwm channels using the same timer have the same frequency, but can have different duty cycles
  • maximum pwm frequency is 40 MHz
  • pwm duty resolution can be 1-15 bits and is automatically set to maximum value for requested frequency.
    The frequency and the duty resolution are interdependent. The higher the PWM frequency, the lower duty resolution is available and vice versa.
>>> PWM.list()
PWM(pin: 21, freq=10000 Hz, duty=25% [1024], duty resolution=12 bits, channel=0, timer=0)
PWM(pin: 23, freq=10000 Hz, duty=9% [409], duty resolution=12 bits, channel=1, timer=0)
PWM(pin: 25, freq=2003 Hz, duty=25% [8192], duty resolution=15 bits, channel=2, timer=2)
PWM(pin: 27, freq=20000 Hz, duty=25% [512], duty resolution=11 bits, channel=3, timer=1)
PWM(pin: 4, freq=20000 Hz, duty=75% [1536], duty resolution=11 bits, channel=4, timer=1)
PWM(pin: 19, freq=10000 Hz, duty=50% [2048], duty resolution=12 bits, channel=5, timer=0)
PWM(pin: 22, freq=2003 Hz, duty=25% [8192], duty resolution=15 bits, channel=6, timer=2)
PWM(pin: 26, freq=10000 Hz, duty=75% [3072], duty resolution=12 bits, channel=7, timer=0)

pwm


Create the pwm instance object

pwm = machine.PWM(pin [, freq=f] [, duty=d] [, timer=tm])

Arg Description
pin esp32 GPIO number to be used as pwm output
can be given as integer value or machine.Pin object
freq optional, default 5 kHz; pwm frequeny in Hz (1 - 40000000)
duty optional, default 50% kHz; pwm duty cycle in % (0 - 100)
timer optional, default 0; pwm timer (0 - 3)

PWM channel is selected automatically from 8 available pwm channels.

pwm.init([ freq=f] [, duty=d] [, timer=tm])

Reinitialize the pwm channel

Arg Description
freq optional, if not given, the frequency is not changed
duty optional, if not given, the duty cycle is not changed
timer optional, if not given, the pwm timer is not changed

Changing the frequency or timer will affect all pwm channels using the same timer.

pwm.deinit()

Deinitialize and free the pwm channel, stop pwm output.

The echannel can be reinitializeded using pwm.init().

pwm.freq([freq])

With no argument, return the current pwm channel frequency.
Set the new pwm frequency to ḟreq Hz.
All pwm channels using the same timer will be affected.

pwm.duty([duty_perc])

With no argument, return the current pwm channel duty cycle.
Set the new pwm duty cycle to duty_perc in %. The value can be given as float.

pwm.pause()

Pause the pwm channel timer, no pwm output will be present on pwm pin.
All pwm channels using the same timer will be affected.

pwm.resume()

Resume the pwm channel timer, pwm output will be present on pwm pin.
All pwm channels using the same timer will be affected.


machine.PWM.list()

List the characteristics of all active pwm channels.


Example

from machine import PWM

# Init all 8 pwm channels to the defaults
pwm1=PWM(21)
pwm2=PWM(23)
pwm3=PWM(25)
pwm4=PWM(27)
pwm5=PWM(4)
pwm6=PWM(19)
pwm7=PWM(22)
pwm8=PWM(26)
# --> Image 1

# Set duty cycles of all pwm channels
pwm1.duty(10)
pwm2.duty(20)
pwm3.duty(30)
pwm4.duty(40)
pwm5.duty(50)
pwm6.duty(60)
pwm7.duty(70)
pwm8.duty(80)
# --> Image 2

# Reinitialize pwm5 to use timer 1 with frequency of 20 kHz
pwm5.init(freq=20000,timer=1)
# --> Image 3


# Set the frequency of pwm1 to 1 MHz
# All channels using the same timer (0) will be affected
# Duty cycles of all channels are preserved
pwm1.freq(1000000)
# --> Image 4

# Set the frequency of pwm5 to 2 MHz
pwm5.freq(2000000)
# --> Image 5

>>> PWM.list()
PWM(pin: 21, freq=1000000 Hz, duty=7% [5], duty resolution=6 bits, channel=0, timer=0)
PWM(pin: 23, freq=1000000 Hz, duty=18% [12], duty resolution=6 bits, channel=1, timer=0)
PWM(pin: 25, freq=1000000 Hz, duty=28% [18], duty resolution=6 bits, channel=2, timer=0)
PWM(pin: 27, freq=1000000 Hz, duty=37% [24], duty resolution=6 bits, channel=3, timer=0)
PWM(pin: 4, freq=2000000 Hz, duty=50% [16], duty resolution=5 bits, channel=4, timer=1)
PWM(pin: 19, freq=1000000 Hz, duty=57% [37], duty resolution=6 bits, channel=5, timer=0)
PWM(pin: 22, freq=1000000 Hz, duty=68% [44], duty resolution=6 bits, channel=6, timer=0)
PWM(pin: 26, freq=1000000 Hz, duty=78% [50], duty resolution=6 bits, channel=7, timer=0)

pwm1 Image 1 pwm2 Image 2 pwm3 Image 3 pwm4 Image 4 pwm5 Image 5

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