permanently running PWM

[drekthrall]

Hello,

my simple python code :

Code: Select all

#!/usr/bin/env python
import RPi.GPIO as GPIO

GPIO.setmode(GPIO.BCM)
GPIO.setup(25, GPIO.OUT)
p = GPIO.PWM(25,200)
p.start(50)

If I execute this script 25GPIO will turn on (on 50%) and immediately turn off. My LED just once blinked.

If I execute script like this :

Code: Select all

import RPi.GPIO as GPIO

GPIO.setmode(GPIO.BCM)
GPIO.setup(25, GPIO.OUT)
GPIO.output(25, True)

The LED will be turned on "forever".

My question is how to run PWM "forever" without any loops like while ... ? Thanks for any response !

[mahjongg]

You just turn PWM on, and it will run "forever" until you give a new PWM control, that turns it off.

[B.Goode]

You just tun PWM on, and it will run "forever" until you give a new PWM control, that turns it off.

What happens when the controlling Python script terminates? Is that the end of 'forever'?

[drekthrall]

You just tun PWM on, and it will run "forever" until you give a new PWM control, that turns it off.

That is not working for me , i need to add time.sleep(x) to let PWM running for x seconds , after time.sleep ends PWM ends too :/

[rpdom]

The software PWM is controlled by the python RPi.GPIOlibrary. As soon as your program terminates it will stop working. You can't do anything about that.

The hardware PWM would keep running independently of any program, but there is only one of those normally available.

[drekthrall]

The software PWM is controlled by the python RPi.GPIOlibrary. As soon as your program terminates it will stop working. You can't do anything about that.

The hardware PWM would keep running independently of any program, but there is only one of those normally available.

Thanks ! That was very helpful for me ! Thanks for help

[drekthrall]

The software PWM is controlled by the python RPi.GPIOlibrary. As soon as your program terminates it will stop working. You can't do anything about that.

The hardware PWM would keep running independently of any program, but there is only one of those normally available.

One more question please ... Is there any Raspberry pi ( 2 A,B ,B+ , ...) that has 2 (or more) HW PWM ? If no, is there any HW PWM module ?

[joan]

pigpio will let you use the two hardware PWM channels available on the A+/B+/Pi2/compute module. It well also let you run hardware timed PWM on the other GPIOs even when the Python script is terminated (as long as the pigpio daemon is left running).

[drekthrall]

pigpio will let you use the two hardware PWM channels available on the A+/B+/Pi2/compute module. It well also let you run hardware timed PWM on the other GPIOs even when the Python script is terminated (as long as the pigpio daemon is left running).

Thanks !
Only for sure Raspberry Pi 2 B has two hardware PWMs ?

[joan]

...
Only for sure Raspberry Pi 2 B has two hardware PWMs ?

http://abyz.co.uk/rpi/pigpio/python.html#hardware_PWM