def __init__(self, ultra_sonic_sensor_timeout):
if type(self) == BaseEngine:
# Prevent direct instatiation of this class
raise NotImplementedError
# Length in time of each move command in seconds
self.ultra_sonic_sensor_timeout = ultra_sonic_sensor_timeout
if os.environ.get('country_bot_env') != "TESTING":
GPIO.setwarnings(False)
global _engine_initialized
if _engine_initialized == False:
self.initialize_engine()
def initialize_engine(self):
"""
These RPi initialization tasks only occur once
"""
# Set up the Raspberry Pi Board configuration
GPIO.setmode(GPIO.BOARD)
# Set up ultrasonic sensor pins
GPIO.setup(self.TRIG_PIN, GPIO.OUT)
GPIO.setup(self.ECHO_PIN, GPIO.IN)
# Set up and reset motor pins
for pin in self.MOTOR_PINS:
GPIO.setup(pin, GPIO.OUT)
global _engine_initialized
_engine_initialized = True
def _move_straight_and_turn(self, turn_pin):
""" Turn car in direction of pin specified """
if not turn_pin in self.MOTOR_PINS:
raise ValueError
# Turn the steering
GPIO.output(turn_pin, True)
time.sleep(self.BRAKE_AND_TURN_PAUSE_TIME)
# Move forward
GPIO.output(self.MOTOR_STRAIGHT_PIN, True)
time.sleep(self.MOVE_DURATION)
# Stop car
self._apply_brakes()
GPIO.output(turn_pin, False)
def get_us_distance(self):
"""
Measures the distance using the ultrasonic sensor. Returns a distance
in cm. Returns `math.inf` if distance cannot be measured
"""
try:
# Send off trigger, and wait for sensor to settle
GPIO.output(self.TRIG_PIN, False)
time.sleep(self.ULTRASONIC_SENSOR_SETTLE_TIME)
# Create the pulse for a short amount of time
GPIO.output(self.TRIG_PIN, True)
time.sleep(0.00001)
GPIO.output(self.TRIG_PIN, False)
pulse_start_time, pusle_end_time = time.time(), time.time()
# grab start time
cycles = 0
while GPIO.input(self.ECHO_PIN) == 0:
pulse_start_time = time.time()
cycles += 1
if cycles > self.ultra_sonic_sensor_timeout:
return math.inf
cycles = 0
while GPIO.input(self.ECHO_PIN) == 1:
pusle_end_time = time.time()
cycles += 1
if cycles > self.ultra_sonic_sensor_timeout:
return math.inf
duration = pusle_end_time - pulse_start_time
return duration * self.SPEED_OF_SOUND / 2
except:
# Error occured, return infinity for distance
return math.inf
def turn_wheels_forward(self):
""" Straighten the wheels """
GPIO.output(self.MOTOR_LEFT_PIN, False)
GPIO.output(self.MOTOR_RIGHT_PIN, False)
def turn_wheels_right(self):
""" Turn wheels to the right, removing pin output to 'left' wheels """
GPIO.output(self.MOTOR_LEFT_PIN, False)
GPIO.output(self.MOTOR_RIGHT_PIN, True)
def __init__(self, ultra_sonic_sensor_timeout=500000):
super().__init__(ultra_sonic_sensor_timeout=ultra_sonic_sensor_timeout)
# Set up PWM pin for slower forward motion
self.pwm = GPIO.PWM(self.MOTOR_STRAIGHT_PIN, self.PWM_FREQUENCY)
def go_straight(self):
""" Moves the car forward for MOVE_DURATION, applying motion to given pin """
GPIO.output(self.MOTOR_STRAIGHT_PIN, True)
time.sleep(self.MOVE_DURATION)
GPIO.output(self.MOTOR_STRAIGHT_PIN, False)
self._apply_brakes()
def _apply_brakes(self):
""" Momentarily applies brakes to prevent car from rolling """
GPIO.output(self.MOTOR_STRAIGHT_PIN, False)
GPIO.output(self.MOTOR_REVERSE_PIN, True)
time.sleep(self.BRAKE_AND_TURN_PAUSE_TIME)
GPIO.output(self.MOTOR_REVERSE_PIN, False)