performing infinite loop while awaiting input

问题

I have a little project I'm working on, it's fairly simple so I'm hoping someone can help me.

I'm using a raspberry pi to dim a single LED with some very crude PWM.

my PWM code looks like this:

import RPi.GPIO as GPIO
import time
GPIO.setmode(GPIO.BCM)
GPIO.setup(7, GPIO.OUT)
frequency = 0.005
dwell = 0.0001
while True:
    time.sleep(frequency)
    GPIO.output(7, 1)
    time.sleep(dwell)
    GPIO.output(7, 0)

Basically, in order for the LED to remain lit at the brightness determined by "dwell" I need that bit of code to continue looping forever.

What I would like to do is use something like

dwell=raw_input('brightness:')

so that while the PWM code is looping, I can drop in a new value for dwell to adjust the brightness of the LED.

all of my efforts so far result in one of the following:

a: the dimming loop executes once only and stops to await input b: the dimming loop will execute infinitely but not allow further input

can one of you fine people provide me with a code example that explains how I can achieve this?

for those interested, ultimately what I would like to do is set the value of dwell via sockets and use a better form of PWM output to drive LED downlights. Baby steps :)

回答1:

It looks like you need multithreading!

# import the module
import threading

# define a function to be called in the other thread
def get_input():
    while True:
        dwell=raw_input()

# create a Thread object
input_thread=threading.Thread(target=get_input)

# start the thread
input_thread.start()

# now enter the infinite loop
while True:
    time.sleep(frequency)
    GPIO.output(7, 1)
    time.sleep(dwell)
    GPIO.output(7, 0)

There's probably something about locks or semaphores or mutex...es (mutices?) missing here, but I don't know much about those. Simple things like this seem to work for me.

来源：https://stackoverflow.com/questions/28790570/performing-infinite-loop-while-awaiting-input

标签

python

input

raspberry-pi

infinite-loop

pwm