Raspberry Pi 控制 LED 基于 CPU 温度与 Python

Question

I'd like some help getting this python code to work with my Raspberry Pi. The goal is to turn on 1 of 3 LED's at a time ( Green, Yellow, and Red ) based on a CPU Temperature Range .

This means:

• Green LED needs to turn ON when temperature range is less than 32ºC.
• Red LED ON if temperature is greater than 37ºC.
• Then Yellow LED ON if temperature is greater than 31ºC or less than 37ºC.

I'm a newbie at coding, so far I can get the temperature to print and only the Red LED turns on and stays on regardless of CPU temperature.

import os
import time
import RPi.GPIO as GPIO


#GREEN=11
#YELLOW=10
#RED=9

GPIO.setwarnings(False)
GPIO.setmode(GPIO.BCM)
GPIO.setup(11,GPIO.OUT)
GPIO.setup(10,GPIO.OUT)
GPIO.setup(9,GPIO.OUT)


def measure_temp():
        temp = os.popen("vcgencmd measure_temp").readline()
        return (temp.replace("temp=","").replace("'C",""))

while True:
        measure_temp()
        if measure_temp<32:
            GPIO.output(11,GPIO.HIGH)
            GPIO.output(10,GPIO.LOW)
            GPIO.output(9,GPIO.LOW)
        if measure_temp>37:
            GPIO.output(9,GPIO.HIGH)
            GPIO.output(10,GPIO.LOW)
            GPIO.output(11,GPIO.LOW)
        if measure_temp>32 or <37
            GPIO.output(10,GPIO.HIGH)
            GPIO.output(11,GPIO.LOW)
            GPIO.output(9,GPIO.LOW)
            print(measure_temp())

#cleanup
c.close()
GPIO.cleanup()

Answer 1

Cool project and your code is close.

I think the main problem is that you get a string from vcgencmd and you are trying to compare that to a number. I would go with something more like this (untested):

#!/usr/bin/env python3

import os
import re
import time
import RPi.GPIO as GPIO

RED, YELLOW, GREEN = 9, 10, 11

GPIO.setwarnings(False)
GPIO.setmode(GPIO.BCM)
GPIO.setup(RED,GPIO.OUT)
GPIO.setup(YELLOW,GPIO.OUT)
GPIO.setup(GREEN,GPIO.OUT)


def measure_temp():
        output = os.popen("vcgencmd measure_temp").readline()
        # Remove anything not like a digit or a decimal point
        result = re.sub('[^0-9.]','', output)
        return float(result)

while True:
        temp = measure_temp()
        if temp<32:
            GPIO.output(GREEN,GPIO.HIGH)
            GPIO.output(YELLOW,GPIO.LOW)
            GPIO.output(RED,GPIO.LOW)
        elif temp>37:
            GPIO.output(RED,GPIO.HIGH)
            GPIO.output(GREEN,GPIO.LOW)
            GPIO.output(YELLOW,GPIO.LOW)
        else:
            GPIO.output(YELLOW,GPIO.HIGH)
            GPIO.output(GREEN,GPIO.LOW)
            GPIO.output(RED,GPIO.LOW)
        print(temp)
        # Let's not affect our temperature by running flat-out full-speed :-)
        time.sleep(1)

#cleanup
c.close()
GPIO.cleanup()

Note also the use of elif which makes it rather easier for testing the final one of your three cases.

I also went for a regex to extract the number from the vcgencmd string because the text may change with different internationalisation - YMMV here.