Python • Problems using PWM in subprocess

Code:

def activate_car_handling(self):        thread = Process(target=self._start_car_handling, args=(self.shared_flag,))        self._threads.append(thread)        thread.start()        def _start_car_handling(self, flag):        self._print_button_explanation()        self._map_all_objects_to_buttons()        while not flag.value:            for event in self._xboxControl.get_controller_events():                button, pressValue = self._xboxControl.get_button_and_press_value_from_event(event)                if self._xboxControl.check_for_exit_event(button):                    self._exit_program(flag)                    break                # get the object to take action based on the button pushed                try:                    self._buttonToObjectDict[button].handle_xbox_input(button, pressValue)                except KeyError: # if key does not correspond to object, then go to next event                    continue                if self._cameraEnabled:                    self._cameraHelper.update_control_values_for_video_feed(self.shared_dict)        print("Exiting car handling")

Code:

import RPi.GPIO as GPIOfrom roboCarHelper import map_value_to_new_scalefrom itertools import chainclass CarHandling:def __init__(self, leftBackward, leftForward, rightBackward, rightForward, enA, enB):self._leftBackward = leftBackwardself._leftForward = leftForwardself._rightBackward = rightBackwardself._rightForward = rightForwardself._enA = enAself._enB = enBself._pwmMinTT = 20 # this needs to be set to the value where the motors start "biting"self._pwmMaxTT = 60self._speed = 0self._turnLeft = Falseself._turnRight = Falseself._goForward = Falseself._goReverse = Falseself._gpioThrottle = {True: GPIO.HIGH, False: GPIO.LOW}GPIO.setup(leftBackward, GPIO.OUT)GPIO.setup(leftForward, GPIO.OUT)GPIO.setup(rightBackward, GPIO.OUT)GPIO.setup(rightForward, GPIO.OUT)GPIO.setup(enA, GPIO.OUT)GPIO.setup(enB, GPIO.OUT)self._pwmA = GPIO.PWM(enA, 100)self._pwmB = GPIO.PWM(enB, 100)self._pwmA.start(0)self._pwmB.start(0)self._controlsDictTurnButtons = {"Left": "D-PAD left","Right": "D-PAD right",}self._controlsDictThrottle = {"Gas": "RT","Reverse": "LT"}self._turnButtons = list(self._controlsDictTurnButtons.values())self._gasAndReverseButtons = list(self._controlsDictThrottle.values())def handle_xbox_input(self, button, pressValue):if button in self._turnButtons:self._prepare_car_for_turning(button, pressValue)self._move_car()elif button in self._gasAndReverseButtons:self._prepare_car_for_throttle(button, pressValue)self._move_car()def car_buttons(self):completeDict = dict(chain(self._controlsDictThrottle.items(), self._controlsDictTurnButtons.items()))return completeDictdef get_current_speed(self):return int(self._speed)def get_current_turn_value(self):if self._turnLeft:return "Left"elif self._turnRight:return "Right"else:return "-"def _change_duty_cycle(self, pwms, speed):for pwm in pwms:pwm.ChangeDutyCycle(speed)def _adjust_gpio_values(self, gpioValues):leftForwardValue, rightForwardValue, leftBackwardValue, rightBackwardValue = gpioValuesGPIO.output(self._leftForward, self._gpioThrottle[leftForwardValue])GPIO.output(self._rightForward, self._gpioThrottle[rightForwardValue])GPIO.output(self._leftBackward, self._gpioThrottle[leftBackwardValue])GPIO.output(self._rightBackward, self._gpioThrottle[rightBackwardValue])def _move_car(self):if self._goForward:if not self._turnLeft and not self._turnRight:gpioValues = [True, True, False, False]elif self._turnLeft:gpioValues = [False, True, False, False]elif self._turnRight:gpioValues = [True, False, False, False]elif self._goReverse:if not self._turnLeft and not self._turnRight:gpioValues = [False, False, True, True]elif self._turnLeft:gpioValues = [False, False, False, True]elif self._turnRight:gpioValues = [False, False, True, False]elif not self._goReverse and not self._goForward:if not self._turnLeft and not self._turnRight:gpioValues = [False, False, False, False]elif self._turnLeft:gpioValues = [False, True, True, False]elif self._turnRight:gpioValues = [True, False, False, True]self._adjust_gpio_values(gpioValues)def _prepare_car_for_turning(self, button, buttonState):stopTurning = Falseif button == "D-PAD left" and buttonState == 1:self._turnLeft = Trueself._turnRight = Falseelif button == "D-PAD right" and buttonState == 1:self._turnLeft = Falseself._turnRight = Trueelse:self._turnLeft = Falseself._turnRight = FalsestopTurning = Trueif not stopTurning:if not self._goForward and not self._goReverse:self._change_duty_cycle([self._pwmA, self._pwmB], self._pwmMaxTT)def _prepare_car_for_throttle(self, button, buttonPressValue):speed = map_value_to_new_scale(buttonPressValue,self._pwmMinTT,self._pwmMaxTT,2)if speed > self._pwmMinTT + 1: # only change speed if over the tresholdif button == "RT":self._goForward = Trueself._goReverse = Falseelif button == "LT":self._goForward = Falseself._goReverse = Trueelse:speed = 0self._goForward = Falseself._goReverse = Falseself._change_duty_cycle([self._pwmA, self._pwmB], speed)self._speed = speeddef cleanup(self):self._pwmA.stop()self._pwmB.stop()