Just to be clear about GPIO.cleanup

Question

I am not so fluent in programming for the Rpi, which I only do in my very few spare time, so I would like some confirmation.

If I put GPIO.cleanup() this cleansups and puts to input all used GPIOs , right?

I ask this very simple question because in the docs of a sensor (ultrasonic) I have there is this code for us to use:

def reading(sensor):
    import time
    import RPI.GPIO as GPIO
    GPIO.setwarnings(False)
    GPIO.setmode(GPIO.BOARD)
    TRIG=11
    ECHO= 13
    if sensor == 0:
        GPIO.setup(TRIG,GPIO.OUT)
        GPIO.setup(ECHO,GPIO.IN)
        time.sleep(0.3)
        GPIO.output(TRIG,True)
        time.sleep(0.00001)
        GPIO.output(TRIG,False)
        while GPIO.input(ECHO) ==0:
            signaloff=time.time()
        while GPIO.input(ECHO) ==1:
            signalon=time.time()
        timepassed=signalon-signaloff
        distance=timepassed*170000
        return distance
        GPIO.cleanup()
    else:
        print"Incorrect usonic() function variable"

print reading(0)

First, I find the implementation of this function not that good. With the imports and the setmode inside the function. But what it bothers me most is that the function includes cleanup

I am planning to use other GPIOs for other sensors as well, But does using the above function once means that it is going to interfere with my own other sensors? I guess it will and that the implementation of this function is wrong.

Any thoughts on this?

Answer 1

Yes, the cleanup() function sets to be inputs all the GPIO used by a RPi.GPIO script. It doesn't effect other RPi.GPIO scripts running at the same time.

That particular script seems to be designed as a one-off which invokes reading() once and then exits. In that context it may not be as poor as it first looks.

Opinion.

Even so I think it poor practice. I would move the initialisation (import time, import RPI.GPIO, setwarnings, setmode, setup) and termintation (cleanup) functions outside the reading() function as generally a much more sensible, usable, and changeable design.

End of opinion.

As long as RPi.GPIO scripts do not use the same resource as another running script multiple scripts may be running at a time.

As an example the following script uses GPIO4 (I prefer BCM numbering). Copy the script and change the USE=4 line to different values for each script. If you then run them in parallel (use & or separate terminal windows per script) you can confirm each works quite happily with the other scripts.

#!/usr/bin/env python

import time
import RPi.GPIO as GPIO

USE=4

GPIO.setmode(GPIO.BCM)
GPIO.setup(USE, GPIO.OUT)

end_time = time.time() + 60

while end_time > time.time():
   print("using {}".format(USE))
   GPIO.output(USE, False)
   time.sleep(0.5)
   GPIO.output(USE, True)
   time.sleep(0.5)

GPIO.cleanup()

Answer 2

GPIO.cleanup() is cleaning up all the ports you’ve used.

It resets the ports you have used in your program back to input mode.