PWM_Python

#!/usr/bin/python3

# from Mark Yoder but changed heavily by me (as you can tell)
# Seth 2022

import glob
import pathlib
from time import sleep

def set_frequency(freq):
    """ Change the frequency

    frequency - frequency in Hz (freq > 0.0) """
    path = "/dev/bone/pwm/1"
    pathpwm = path + "/b"

    # compute current duty cycle
    fd = open(pathpwm + "/duty_cycle", 'r')
    duty_cycle_ns = int(fd.read())
    fd.close()

    fd = open(pathpwm + "/period", 'r')
    period_ns = int(fd.read())
    fd.close()

    duty_cycle = duty_cycle_ns/period_ns          # compute current duty cycle as fraction
    period_ns = 1e9 / freq                  # compute new period
    duty_cycle_ns = period_ns*duty_cycle # compute new duty cycle as fraction of period

    # print('duty_cycle: ' + str(duty_cycle))
    # print('period_ns: ' + str(period_ns))
    # print('duty_cycle_ns: ' + str(duty_cycle_ns))

    # Duty Cycle - Set to 0
    fd = open(pathpwm + "/duty_cycle", 'w')
    fd.write('0')
    fd.close()

    # Period
    fd = open(pathpwm + "/period", 'w')
    fd.write(str(int(period_ns)))
    fd.close()

    # Duty Cycle
    fd = open(pathpwm + "/duty_cycle", 'w')
    fd.write(str(int(duty_cycle_ns)))
    fd.close()

def set_duty_cycle(duty):
    """ Change the duty cycle.

    dutycycle - between 0.0 and 100.0 """
    path = get_pwm_path()
    pathpwm = path + "/b"

    fd = open(pathpwm + "/period", 'r')
    period_ns = int(fd.read()[:-1])
    fd.close()

    duty_cycle_ns = duty/100 * period_ns
    # Duty Cycle
    fd = open(pathpwm + "/duty_cycle", 'w')
    fd.write(str(int(duty_cycle_ns)))
    fd.close()

def stop():
    """ Stop the PWM channel. """

    path = pwm_path()
    pathpwm = path + "/b"

    # Disable
    fd = open(pathpwm + "/enable", 'w')
    fd.write('0')
    fd.close()

    # unexport
    fd = open(path + "/unexport", 'w')
    fd.write(str(path[1]))
    fd.close()