A simple Python class to work with the Linux PWM kernel driver.
Written for the Raspberry Pi and the hardware pwm timers, but should work with other SOCs.
Requires that a PWM kernel driver is loaded appropriately which on the RPi normally means a dts overlay.
Instructions for building and loading an appropriate dts for the RPi can be found here.
I'm using a custom Yocto built O/S where pwm overlays are installed by default.
Here is a simple interactive example using the PWM class
root@rpi3:~# python3 Python 3.5.2 (default, Nov 22 2016, 06:54:46) [GCC 6.2.0] on linux Type "help", "copyright", "credits" or "license" for more information.
Import the PWM class from
>>> from pwm import PWM
Create an instance of the class for the PWM0 timer
>>> pwm0 = PWM(0)
Call export() before first use
Setup a 1 ms period, 25% duty cycle pulse (period and duty_cycle units are nanoseconds)
>>> pwm0.period = 1000000 >>> pwm0.duty_cycle = 250000
Start the pwm timer
>>> pwm0.enable = True
Change the duty cycle to 50%
>>> pwm0.duty_cycle = 500000
Turn off the timer
>>> pwm0.enable = False
Create an instance for the PWM1 timer
>>> pwm1 = PWM(1) >>> pwm1.export()
Setup a servo-like pulse with a 50 ms period and 2 ms duty_cycle
>>> pwm1.period = 50000000 >>> pwm1.duty_cycle = 2000000 >>> pwm1.enable = True
Set the servo pulse to 2.5 ms
>>> pwm1.duty_cycle = 2500000
Set the servo pulse to 1.5 ms
>>> pwm1.duty_cycle = 1500000
Back to 2.0 ms
>>> pwm1.duty_cycle = 2000000
Turn it off
>>> pwm1.enable = False
Unexport both timers
>>> pwm0.unexport() >>> pwm1.unexport() >>> quit()