dtoverlay=pwm-2chan has no effect on RPi 5

[schech1]

I added dtoverlay=pwm-2chan to /boot/config.txt on a Raspberry Pi 5, but lsmod | grep pwm does not show any output.
Also there is no pwm-signal generated either on GPIO19 or 18.

[CamDavidsonPilon]

Hi @schech1, are you using the latest version (0.2.1, check with pip list). If not, please upgrade. The RPi5 is supported by adding chip=2, ex: HardwarePWM(..., chip=2)

[schech1]

Yes, I'm using 0.2.1 and i also used chip=2.
I also believe that issue is not really related with rpi_hardware_pwm.
But should I see pwm_bcm2835 when using lsmod | grep pwm on a RPi5 after reboot?

[CamDavidsonPilon]

Testing on my Rpi5, no, I don't see lsmod | grep pwm return anything

[schech1]

I'm trying to figure out what I do wrong.
I connected an LED to GPIO 18 and ran this simple test:

from gpiozero import PWMLED
from rpi_hardware_pwm import HardwarePWM
from time import sleep

# Not working
pwm = HardwarePWM(pwm_channel=0, hz=60, chip=2)
pwm.start(100) 
sleep(2)
pwm.stop()

# Working
led = PWMLED(18, frequency = 200) 
led.value = 1
sleep(1)
led.value = 0

Using gpiozero on the same pin, it works.
Is there anything I can do to investigate further?

[CamDavidsonPilon]

hm, try the following in boot/config.txt (this is from my RPi5):

dtoverlay=pwm-2chan,pin=12,func=4,pin2=13,func2=4

then try the same code, but targeting pin 12. Maybe something is different with the other pins?

[schech1]

Yeah, that works.
Got it working no on pin 12 and 13.

[CamDavidsonPilon]

Okay, interesting, something must be different with RPi5 for the original pins. I'll have to investigate later though.

[somsubhro88]

This solution works for me as well. Thank you for this library!!

[wayneOS1337]

I still got problems on Pi5.

config.txt:
dtoverlay=pwm-2chan,pin=12,func=4,pin2=13,func2=4

python:
pwm = HardwarePWM(pwm_channel=1, hz=frequency, chip=2)
pwm.start(50)

I get no PWM output on Pin 13. What am i missing? Thanks in advance.

[CamDavidsonPilon]

@wayneOS1337 not sure - did you do a reboot? Can you paste here your entire config.txt file?

[wayneOS1337]

Yes, i did a reboot. My config.txt is:

# For more options and information see
# http://rptl.io/configtxt
# Some settings may impact device functionality. See link above for details

# Uncomment some or all of these to enable the optional hardware interfaces
#dtparam=i2c_arm=on
#dtparam=i2s=on
#dtparam=spi=on

# Enable audio (loads snd_bcm2835)
dtparam=audio=on

# Additional overlays and parameters are documented
# /boot/firmware/overlays/README

# Automatically load overlays for detected cameras
camera_auto_detect=1

# Automatically load overlays for detected DSI displays
display_auto_detect=1

# Automatically load initramfs files, if found
auto_initramfs=1

# Enable DRM VC4 V3D driver
dtoverlay=vc4-kms-v3d
max_framebuffers=2

# Don't have the firmware create an initial video= setting in cmdline.txt.
# Use the kernel's default instead.
disable_fw_kms_setup=1

# Run in 64-bit mode
arm_64bit=1

# Disable compensation for displays with overscan
disable_overscan=1

# Run as fast as firmware / board allows
arm_boost=1

[cm4]
# Enable host mode on the 2711 built-in XHCI USB controller.
# This line should be removed if the legacy DWC2 controller is required
# (e.g. for USB device mode) or if USB support is not required.
otg_mode=1

[all]
dtoverlay=pwm-2chan,pin=12,func=4,pin2=13,func2=4

So basically i just added the pwm-2chan line on the end. I did this previously on a Pi4 and everythings was working smooth with "rpi_hardware_pwm".

But my guess is that the dtoverlay is not working correctly. After reboot i get for:

$ pinctrl get 12,13

12: no pd | -- // PIN32/GPIO12 = none
13: no pd | -- // PIN33/GPIO13 = none

i also tried to just use dtoverlay=pwm-2chan or dtoverlay=pwm in config.txt, to use it with the default GPIO 18 but to no avail.

[CamDavidsonPilon]

There is an errant ` at the end of the last line of your config.txt: is that a type in github or your config?

[wayneOS1337]

Yes, sorry that was a typo in my comment. i edited my comment. The file is without it.

[CamDavidsonPilon]

Not sure! How are you measuring PWM on a pin?

[wayneOS1337]

I tested it with a Servo (same settings as on the Pi4) and also with a LED. Did you use Bookworm as OS? or is there any additional Software i need to install?

[valtsu23]

I have the same issue with Rpi 5. Even with dtoverlay=pwm lsmod | grep pwm gives nothing.
pinctrl get 18 gives: 18: a3 pd | lo // PIN12/GPIO18 = PWM0_CHAN2

I see this error on startup:
clk: couldn't set clk_pwm0 clk rate to 100000000 (-22), current rate: 30720000

[valtsu23]

Problem is the pwmchip index.
https://forums.raspberrypi.com/viewtopic.php?t=359251&sid=5c309b2e5afd4af2b928bda747f4296b#p2154764

I wanted to use GPIO18 pwm (dtoverlay=pwm added to config.txt).
I used: HardwarePWM(pwm_channel=2, hz=60, chip=2)
Modified a line to accept more channels: https://github.com/Pioreactor/rpi_hardware_pwm/blob/main/rpi_hardware_pwm/__init__.py#L41

Works as it should. I haven't tested any other channels or GPIO:s.

[CamDavidsonPilon]

I've released a 0.2.2 version that allows for more chips, thanks to @colinpate for the PR

[bbfjumper]

Hi there, I`m having a simliar issue.

the command pwm = HardwarePWM(pwm_channel=0, hz=100, chip=2) throws the follwing error:

[Errno 22] Invalid argument
File "/home/raspi4/Projects/scripts/control_motor.py", line 7, in set_motor_speed
    pwm = HardwarePWM(pwm_channel=0, hz=100, chip=2)

See attachement for /boot/firmware/config.txt file
config.txt

Thanks a lot for helping!

[valtsu23]

Hi,
Try this: pwm = HardwarePWM(pwm_channel=2, hz=100, chip=2)
If it doesn't work, please post your full code.

[bbfjumper]

Hi, thanks for the fast replay.

that leads to the same error:
Exception has occurred: OSError [Errno 22] Invalid argument

my full code is:

from rpi_hardware_pwm import HardwarePWM
import time
from loguru import logger


def set_motor_speed(speed: int) -> None:
    pwm = HardwarePWM(pwm_channel=2, hz=100, chip=2)
    pwm.start(100)  # full duty cycle
    time.sleep(3)
    pwm.change_duty_cycle(20)

    pwm.stop()

    duty_cycle = 10 + (speed / 9000) * 80


def stop_motor() -> None:
    pass
    # pwm.change_duty_cycle(10)
    # pwm.stop()


def read_values() -> tuple:
    pass


if __name__ == "__main__":
    set_motor_speed(9000)

[CamDavidsonPilon]

@bbfjumper perhaps is a kernel issue: https://forums.raspberrypi.com/viewtopic.php?t=367294 (a new kernel was released in the 24-03-12 image)

I'll be watching that thread for more

[bbfjumper]

okay that could be the solution, i assume downgrading would solve the problem, what kernel version are you using?

[CamDavidsonPilon]

I'm using the 6.1.63, from the 2023-12-11 release.

[l4cer]

I'm having the same invalid argument issue with my Raspberry Pi 5 kernel 6.6. Could you instruct me on how to downgrade the kernel to 6.1.63? When I use the legacy version of the 6.1 kernel from Raspberry Pi Imager v1.8.5 for RPi 5, I just can't finish the boot...

[CamDavidsonPilon]

When I use the legacy version of the 6.1 kernel from Raspberry Pi Imager v1.8.5 for RPi 5, I just can't finish the boot...

Try downloading an older image from here: https://www.raspberrypi.com/software/operating-systems/

[bbfjumper]

with downgrading my kernel to 6.1.63 it works, thanks everbody for helping me.

I downgraded with sudo rpi-update 3cfd50755ffbb2f952408b59df1a9a63d3af5387
with SHA from: https://github.com/raspberrypi/rpi-firmware/commits/master/?after=f63715223f7cf0ce0cb3be57361ecab8d917699c+34

[valtsu23]

The Kernel issue seems to be fixed in 6.6.22 version. I had the same error with 6.6.20, but not with 6.6.22.

[geekworm-com]

Yes, after updating the kernel from 6.6.20 to 6.6.22, the PWM fan started working properly.

[Schwarzkopf-Henkal]

Encountered same Invalid Argument issue with my Raspberry Pi5 on Ubuntu 24.04 Kernel 6.8.0.

Linux ubuntu 6.8.0-1007-raspi #7-Ubuntu SMP PREEMPT_DYNAMIC Mon Jun 24 10:21:12 UTC 2024 aarch64 aarch64 aarch64 GNU/Linux

My code is as followed

from rpi_hardware_pwm import HardwarePWM
from time import sleep
pwm=HardwarePWM(0,60,chip=2)#channel 0 1 2 3 for GPIO12 13 18 19 respectively
pwm.start(100)
pwm.change_duty_cycle(0.5/10)
# pwm.change_frequency(25_000)
sleep(2)
pwm.stop()

added dtoverlay=pwm-2chan,pin=12,func=4,pin2=13,func2=4 to config.txt

When I execute the code without sudo, I got error log as followed

Traceback (most recent call last):
  File "/home/pi/C2/hardwarepwm.py", line 3, in <module>
    pwm=HardwarePWM(0,60,chip=2)#channel 0 1 2 3 for GPIO12 13 18 19 respectively
        ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.12/dist-packages/rpi_hardware_pwm/__init__.py", line 56, in __init__
    raise HardwarePWMException(f"Need write access to files in '{self.chippath}'")
rpi_hardware_pwm.HardwarePWMException: Need write access to files in '/sys/class/pwm/pwmchip2'

When I execute the code with sudo, I got error log showing Invalid Argument

OSError: [Errno 22] Invalid argument

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/pi/C2/hardwarepwm.py", line 5, in <module>
    pwm.change_duty_cycle(0.5/10)
  File "/usr/local/lib/python3.12/dist-packages/rpi_hardware_pwm/__init__.py", line 105, in change_duty_cycle
    self.echo(dc, os.path.join(self.pwm_dir, "duty_cycle"))
  File "/usr/local/lib/python3.12/dist-packages/rpi_hardware_pwm/__init__.py", line 78, in echo
    with open(file, "w") as f:
OSError: [Errno 22] Invalid argument

[alectutin-qut]

For anyone experiencing this issue, following the instructions on this Gist worked for me!

[ilw]

For anyone else who gets stuck on this on a Pi5:
Adding the following to /boot/firmware/config.txt (Bookworm version of raspbian moved this file from /boot/config.txt)

dtoverlay=pwm-2chan

Then rebooting will enable PWM (chip 2 channel 2) on GPIO 18.
This can be seen if you run:
pinctrl get | grep PWM

it will show GPIO 18 and the fan as being active.

Only certain pins can be configured for hardware PWM. see: https://community.element14.com/products/raspberry-pi/m/files/148385

To enable an additional PWM channel you could change the line to

dtoverlay=pwm-2chan,pin2=19

and reboot, which will also enable GPIO 19 (chip 2, channel 3). If you want to use the other channels/pins you need to follow the other instructions in the readme.md of this repo. Also info can be found by running

dtoverlay -h pwm-2chan

Other useful commands:
sudo cat /sys/kernel/debug/pwm
lsmod | grep pwm