Exception using PWM

[DieterHolz]

I tried to get the PWM example "BuzzerApp" from "pi4j-example-components" working according to blogpost https://www.pi4j.com/blog/2024/20240423_pwm_rpi5/

Code is on branch "Pi5"

As far as I remember it worked sometimes, but now it throws this exception when calling pwm.off().

The rest seems to work (the buzzer makes the expected noise)

[main] ERROR com.pi4j.plugin.linuxfs.provider.pwm.LinuxFsPwm - Invalid argument
java.io.IOException: Invalid argument
at java.base/sun.nio.ch.UnixFileDispatcherImpl.write0(Native Method)
at java.base/sun.nio.ch.UnixFileDispatcherImpl.write(UnixFileDispatcherImpl.java:65)
at java.base/sun.nio.ch.IOUtil.writeFromNativeBuffer(IOUtil.java:137)
at java.base/sun.nio.ch.IOUtil.write(IOUtil.java:102)
at java.base/sun.nio.ch.IOUtil.write(IOUtil.java:72)
at java.base/sun.nio.ch.FileChannelImpl.write(FileChannelImpl.java:300)
at java.base/sun.nio.ch.ChannelOutputStream.writeFully(ChannelOutputStream.java:68)
at java.base/sun.nio.ch.ChannelOutputStream.write(ChannelOutputStream.java:105)
at java.base/java.nio.file.Files.write(Files.java:3510)
at java.base/java.nio.file.Files.writeString(Files.java:3727)
at java.base/java.nio.file.Files.writeString(Files.java:3667)
at com.pi4j.plugin.linuxfs.internal.LinuxPwm.setEnabled(LinuxPwm.java:244)
at com.pi4j.plugin.linuxfs.internal.LinuxPwm.disable(LinuxPwm.java:221)
at com.pi4j.plugin.linuxfs.provider.pwm.LinuxFsPwm.off(LinuxFsPwm.java:161)
at com.pi4j.catalog.components.Buzzer.off(Buzzer.java:77)
at com.pi4j.catalog.components.Buzzer.(Buzzer.java:44)
at com.pi4j.catalog.applications.BuzzerApp.main(BuzzerApp.java:56)
Exception in thread “main” com.pi4j.io.exception.IOException: Unable to disable (OFF) PWM [2] @ </sys/class/pwm/pwmchip2/pwm2>; Invalid argument
at com.pi4j.plugin.linuxfs.provider.pwm.LinuxFsPwm.off(LinuxFsPwm.java:168)
at com.pi4j.catalog.components.Buzzer.off(Buzzer.java:77)
at com.pi4j.catalog.components.Buzzer.(Buzzer.java:44)
at com.pi4j.catalog.applications.BuzzerApp.main(BuzzerApp.java:56)

pi4j.com
PWM Hardware Support on RPi5 - Pi4J
Java IO Library for the Raspberry Pi
5:11

[taartspi]

@DieterHolz I set up my Pi5 using your Pi5 branch. I can go to the Application package BuzzerApp and run your app. As I don't have a buzzer just watching a connected LED and I see the program functions. This is working ok.

Is there a different manner I should us to run the application ?
Or is it just repeat execution and see if I hit the exception ?
thanks

[DieterHolz]

@taartspi
It must be a setup problem of the Pi, then. The exception occurs every single time if you call pwm.off()

I've just added

dtoverlay=pwm-2chan

to the config.txt.

Is there anything else to do?

[taartspi]

pi@rasp5Dev:/sys/class/pwm/pwmchip2 $ ls
device export npwm power subsystem uevent unexport
pi@rasp5Dev:/sys/class/pwm/pwmchip2 $ ls
device export npwm power pwm2 subsystem uevent unexport
pi@rasp5Dev:/sys/class/pwm/pwmchip2 $

Of significance, the channel has been enabled, so pwm.off() can function.

This is my bug. If the first thing attempted is off, I do not enable channel. So, while I fix this, If your team wants to make progress on this test, in the Buzzer class, after creating the configBuilder, comment out the off().

I am busy much of Monday and Tuesday and may find it difficult to fix this that soon. Tom...

So the other night when I could not duplicate you error, I first used a pwm tests of my own and it enabled the channel, so than your tests would function for me.

[DieterHolz]

Take your time.

Avoiding an initial pwm.off() is an easy, good enough workaround.

[taartspi]

The bug Dieter hit is specific to my provider so this case in pigpio needs separate attention

[FDelporte]

@taartspi thanks, deleted, will make separate ticket