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#!/usr/bin/env python
# Import required modules
import RPi.GPIO as GPIO
from time import sleep
# Constants: parameters that the caller cannot modify
# Frequency: We have determined that the optimal frequency for our motor is 1kHz
pwm_frequency = 1000
# Motor Class
# This controls the motor at the given IO
class Motor:
def __init__(self, speed_pin, forward_pin, reverse_pin):
# Set the board IO (just in case it hasn't been done yet)
GPIO.setmode(GPIO.BCM)
# Set our variables for the directional pins
self.forward_pin = forward_pin
self.reverse_pin = reverse_pin
# setup the IO
GPIO.setup(speed_pin, GPIO.OUT)
GPIO.setup(self.forward_pin, GPIO.OUT)
GPIO.setup(self.reverse_pin, GPIO.OUT)
# Set speed pin as a PWM output
self.speed_pwm = GPIO.PWM(speed_pin, pwm_frequency)
self.current_speed = 0.
# END __init__
# Move the motor at a given speed, given as a floating point percentage (-100 <= x <= 100)
# If speed is less than 0, motor will run in reverse, otherwise it will run forward
def move(self, speed):
if speed == self.current_speed:
# do not attempt to readjust speed; this can cause erratic behavior
return
if speed < -100.0 or speed > 100.0:
return
# Stop any previous movements
self.speed_pwm.stop()
# Set the duty cycle for the speed of the motor
self.speed_pwm.ChangeDutyCycle(abs(speed))
if speed < 0:
# Set direction to reverse
GPIO.output(self.forward_pin, GPIO.LOW)
GPIO.output(self.reverse_pin, GPIO.HIGH)
else:
# Set the direction to forward
GPIO.output(self.forward_pin, GPIO.HIGH)
GPIO.output(self.reverse_pin, GPIO.LOW)
# Start the PWM output to start moving the motor
self.speed_pwm.start(abs(speed))
self.current_speed = speed
sleep((1./pwm_frequency) * 3)
# END Move
# Stop the motor from spinning.
# To brake the motor, both direction outputs are set to HIGH
def brake(self):
# Stop any current PWM signals
self.speed_pwm.stop()
# Set the direction outputs to brake
GPIO.output(self.forward_pin, GPIO.HIGH)
GPIO.output(self.reverse_pin, GPIO.HIGH)
self.current_speed = 0.
# END Brake
# Set the motor to coast (i.e. Do not provide power to the motor, but still allow it to spin)
# To coast the motor, both direction outputs are set to LOW
def coast(self):
# Stop any current PWM signals
self.speed_pwm.stop()
# Set the direction outputs to coast
GPIO.output(self.forward_pin, GPIO.LOW)
GPIO.output(self.reverse_pin, GPIO.LOW)
self.current_speed = 0.
# END Coast
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