PIGPIO problem with delay on scripts

Question

I am trying to run an old Raspberry Pi 2011.12 as a server to control a RGB LED strip. To this I am using PIGPIO since this is the best solution (RPi.GPIO is software based, which creates flickering). However I have problems with a small delay, when trying to run the python script.

My code is as follows:

#!/usr/bin/env python

import time, sys, random

import pigpio

pi = pigpio.pi() # connect to local Pi

redcolor = 0
bluecolor = 0
greencolor = 0

pi.set_PWM_dutycycle(23, redcolor)
pi.set_PWM_dutycycle(24, greencolor)
pi.set_PWM_dutycycle(22, bluecolor)

pi.stop()

I have not tried to run the script on a new Raspberry Pi yet since I hope that somebody here could tell me if the delay sounds normal or if there is a way to reduce it. We are talking about approximately 2 seconds before the PWM signal turns on and light up the RGB LED strip.

I am running on Raspbian Buster (the newest version).

Answer 1

On a Pi Zero W it takes just less than half a second for that script to start PWM.

I'd guess that the bulk of the delay is due to the Python module imports.

To facilitate timing I changed the script to the following.

#!/usr/bin/env python

import time, sys, random

import pigpio

pi = pigpio.pi() # connect to local Pi

redcolor = 128
bluecolor = 128
greencolor = 128

pi.set_PWM_dutycycle(17, redcolor)
pi.set_PWM_dutycycle(18, greencolor)
pi.set_PWM_dutycycle(19, bluecolor)

time.sleep(0.5)

pi.set_PWM_dutycycle(17, 0)
pi.set_PWM_dutycycle(18, 0)
pi.set_PWM_dutycycle(19, 0)

pi.stop()

I timed it by running piscope then doing

gpio -g write 4 0; python led.py; gpio -g write 4 1

I can sort of confirm Python initialisation is the problem.

Using pigs the delay is about 20 milliseconds.

gpio -g write 4 0; pigs p 17 128 mils 500 p 17 0; gpio -g write 4 1