Fix PWM bug when pin already exported

[salamantos]

Problem

If pin was already in use, you will get error:

Traceback (most recent call last):
  File "/home/orangepi/feeder/start.py", line 11, in <module>
    PWM_Class.start_pwm()
  File "/usr/local/lib/python3.10/dist-packages/OPi/GPIO.py", line 749, in start_pwm
    return sysfs.PWM_Duty_Cycle_Percent(self.chip, self.pin, self.duty_cycle_percent)  # duty cycle controls the on-off
  File "/usr/local/lib/python3.10/dist-packages/OPi/sysfs.py", line 164, in PWM_Duty_Cycle_Percent
    with open(path, "w") as fp:  # pretty sure this
OSError: [Errno 22] Invalid argument

and PWM will not be enabled

Solution

This is due to try-except in PWM init method: if device already in use, it re-exports, but skips enabling and duty-cycle set

So I just moved latter logic after try-except block