RaspberryPi 与 Python：如何停止伺服并重新启动

Question

When i stop the servo after an action and want to start it again the servo is moving strange. The servo seems to move out of range.

import RPi.GPIO as GPIO
import time

GPIO.setup(17, GPIO.OUT)
p = GPIO.PWM(17, 50)
p.start(2.5)
time.sleep(3)
p.ChangDutyCycle(12.5)
time.sleep(3)
p.ChangDutyCycle(2.5)
time.sleep(3)
p.stop()
p.start(2.5)
# this is not working
p.ChangDutyCycle(12.5)
p.stop()

The servo should normally start again and make the movement. It think it maybe sets the start position wrong and wants to move in the other direction.

Answer 1

Alternately, you can use my library which hides most of the pwm and GPIO board complexity. Sample code:

from RaspberryMotors.motors import servos
s1 = servos.servo(11)  #create the servo objects , connected to GPIO board pin #11 
s1.setAngleAndWait(45) # move S1 position of 45 degrees
s1.shutdown()  #will clean up the GPIO board as well

You can view download the code or the library via any of the two links: https://github.com/vikramdayal/RaspberryMotors or https://pypi.org/project/RaspberryMotors/#description

Answer 2

I solved the problem not very elegant, but I didn't found any better solution. I made an extra file with all the servo moves and executed it with os.system("path to file") in the main program. In the separate file I initialized the servo pins and started the servo. At the end I stopped the servo and cleaned only the servo pins to not break the main program with other pins involved. The problem is that you have to set the servos back to the start position at the end of the separate file.

Answer 3

Not sure it is correct, but, after the stop if you create again the PWM it works. So:

p = GPIO.PWM(17, 50)
p.start(2.5)
time.sleep(3)
p.ChangDutyCycle(12.5)
p.stop()

# create it again
p = GPIO.PWM(17, 50)
p.start(12.5)
time.sleep(3)
p.ChangDutyCycle(4)
p.stop()