Raspberry Pi：GPIO，连续输出GPIO.HIGH

Question

I have a Raspberry Pi installed to switch on some relays. The script is super simple:

import RPi.GPIO as GPIO

RELAY_PIN_1 = 18
RELAY_PIN_2 = 19
RELAY_PIN_3 = 20
RELAY_PIN_4 = 21

def main():
    GPIO.setmode(GPIO.BCM)

    GPIO.setup(RELAY_PIN_1, GPIO.OUT)
    GPIO.setup(RELAY_PIN_2, GPIO.OUT)
    GPIO.setup(RELAY_PIN_3, GPIO.OUT)
    GPIO.setup(RELAY_PIN_4, GPIO.OUT)

    GPIO.output(RELAY_PIN_1, GPIO.HIGH)
    GPIO.output(RELAY_PIN_2, GPIO.HIGH)
    GPIO.output(RELAY_PIN_3, GPIO.HIGH)
    GPIO.output(RELAY_PIN_4, GPIO.HIGH)

if __name__ == "__main__":
    main()   

My question is simple, do I need to keep outputting GPIO.HIGH to all the pins in a while loop, or, will the signal remain high as long as the Raspberry Pi is still powered?

Answer 1

it will remain high until

• you tell it to go low with GPIO.ouptut(xxxx,GPIO.LOW)
• you switch the pin to input
• you turn off the pi (obviously) ...

sometimes pins float a little so you might need a resistor in there somewhere (I think rpi has internal resistors for gpio iirc)

it would have taken almost no time just to run this code and see for yourself :P