#!/usr/bin/python
# -*- coding: utf-8 -*-
import RPi.GPIO as GPIO
import time
import sys
import os
import signal
# Configuration
FAN_PIN = 14 # BCM pin used to drive transistor's base
WAIT_TIME = 5 # [s] Time to wait between each refresh
FAN_LSPD = 20 # [%] Fan minimum speed.
PWM_FREQ = 25 # [Hz] Change this value if fan has strange behavior
# Setup GPIO pin
GPIO.setmode(GPIO.BCM)
GPIO.setup(FAN_PIN, GPIO.OUT, initial=GPIO.LOW)
fan=GPIO.PWM(FAN_PIN,PWM_FREQ)
fan.start(0);

def getCPUtemperature():
    res = os.popen('/opt/vc/bin/vcgencmd measure_temp').readline()
    temp =(res.replace("temp=","").replace("'C\n",""))
print("Temp is {0}°C".format(temp)) #Uncomment here for testing
return temp
def getTEMP():
    CPU_temp = float(getCPUtemperature())
    return()
i = 0
hyst = 1 # Fan speed will change only of the difference of temperature is higher than hysteresis
tempSteps = [30, 35, 40, 45, 50, 60, 65, 70] # [°C] # Configurable temperature and fan speed steps
speedSteps = [0, 20, 40, 60, 80, 100, 100, 100] # [%]
cpuTempOld=0
fanSpeedOld=0
# We must set a speed value for each temperature step
if(len(speedSteps) != len(tempSteps)):
    print("Numbers of temp steps and speed steps are different")
exit(0)

try:
    while 1:
        getTEMP()
        time.sleep(5) # Read the temperature every 5 secs
        cpuTempFile=open("/sys/class/thermal/thermal_zone0/temp","r")
        cpuTemp=float(cpuTempFile.read())/1000
        cpuTempFile.close() # Read CPU temperature
if (abs(cpuTemp-cpuTempOld > hyst)):  #Calculate desired fan speed
if (cpuTemp < tempSteps[0]): # Below first value, fan will run at min speed.
fanSpeed = speedSteps[0]
elif(cpuTemp >= tempSteps[len(tempSteps)-1]): # Above last value, fan will run at max speed
fanSpeed = speedSteps[len(tempSteps)-1]
else: # If temperature is between 2 steps, fan speed is calculated by linear interpolation
for i in range(0,len(tempSteps)-1):
if((cpuTemp >= tempSteps[i]) and (cpuTemp < tempSteps[i+1])):
fanSpeed = round((speedSteps[i+1]-speedSteps[i])\
/(tempSteps[i+1]-tempSteps[i])\
*(cpuTemp-tempSteps[i])\
+speedSteps[i],1)
if((fanSpeed != fanSpeedOld) ):
if((fanSpeed != fanSpeedOld)\
and ((fanSpeed >= FAN_LSPD) or (fanSpeed == 0))):
fan.ChangeDutyCycle(fanSpeed)
fanSpeedOld = fanSpeed
print("Speed is {0}%".format(fanSpeed))
time.sleep(WAIT_TIME) # Wait until next refresh
except(KeyboardInterrupt): # If a keyboard interrupt occurs (ctrl + c), the GPIO is set to 0 and the program exits.
    print("Cancelled... Fan OFF")
    GPIO.cleanup()
    sys.exit()