Processor under high load when using multiple GPIO

Question

Soo here is the thing. I have a script with a function delayedRing(params), which "activates" 3 GPIOs at the same time (or with delay, which is set with parameters), like so:

LED1 ON -> delay -> LED2 ON -> delay -> LED3 -> duration -> LED1 OFF -> delay -> LED2 OFF -> delay -> LED3 OFF

Here is the code:

def delayedRing(interval, duration, bellCount, delay):
    try:
        msg = "rang at " + getCurrentDate() + ' ' + getCurrentTime() + '\n'
        f = open('/home/pi/zvonci/log.txt', 'a')
        f.write(msg.encode('utf-8'))
        f.close()
    except:
        print("error writing to file")

    offLeds = 0
    currentMs = time.clock()

    while offLeds < bellCount:
        ms = time.clock() - currentMs

        if ms < duration:
            GPIO.output(V, GPIO.HIGH)
            if ms >= interval:
                GPIO.output(S, GPIO.HIGH)
                if ms >= 2 * interval:
                     GPIO.output(M, GPIO.HIGH)

        elif offLeds == 0:
            offLeds += 1
            GPIO.output(V, GPIO.LOW)
        if offLeds == 1 and ms >= float(duration + interval):
            offLeds += 1
            GPIO.output(S, GPIO.LOW)
        if offLeds == 2 and ms >= float(duration + 2 * interval):
            offLeds += 1
            GPIO.output(M, GPIO.LOW)

It is working perfectly, but when the code is executing, the processor is under very high load (100% load for the whole duration), which is logical, since it is "activating" GPIOs everytime it loops over the code.

The question is, should I optimize my code, so it sends the signal only twice (when it is turned on and off) or should I let it be as it is?

This piece of code is run once or twice a day for ~4 minutes so it is not a lot.

Answer 1

If you add a time.sleep(0.01) into the while loop, it will use a lot less time.

I modified the code slightly for my convenience but it seems to work.

#!/usr/bin/env python

import time
import pigpio

V=23
S=24
M=25

def delayedRing(interval, duration, bellCount, delay):

    offLeds = 0
    currentMs = time.time()

    while offLeds < bellCount:
        ms = time.time() - currentMs

        #print(offLeds, bellCount, ms, duration)

        if ms < duration:
            pi.write(V, pigpio.HIGH)
            if ms >= interval:
                pi.write(S, pigpio.HIGH)
                if ms >= 2 * interval:
                     pi.write(M, pigpio.HIGH)

        elif offLeds == 0:
            offLeds += 1
            pi.write(V, pigpio.LOW)
        if offLeds == 1 and ms >= float(duration + interval):
            offLeds += 1
            pi.write(S, pigpio.LOW)
        if offLeds == 2 and ms >= float(duration + 2 * interval):
            offLeds += 1
            pi.write(M, pigpio.LOW)

        time.sleep(delay)

pi = pigpio.pi()
if not pi.connected:
   exit(0)

delayedRing(2, 10, 3, 0.1)

pi.stop()

I guess it must depend on the values you are using for interval, duration, bell count, and delay.

As a matter of interest why not just use

LED1 ON
time.sleep(delay)
if bellcount > 1
   LED2 ON
   time.sleep(delay)
   if bellcount > 2
      LED3 ON
time.sleep(duration)
LED1 OFF
time.sleep(delay)
LED2 OFF
time.sleep(delay)
LED3 OFF