# BBB: Bullseye 22-07-01: pwm does not work **URL:** \ **Category:** Linux Discussions\ **Created:** [July 28, 2022, 9:10am UTC](https://forum.digikey.com/t/bbb-bullseye-22-07-01-pwm-does-not-work/24223 "2022-07-28T09:10:56Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![yrrah53](https://avatars.discourse-cdn.com/v4/letter/y/8797f3/32.png) [@yrrah53](https://forum.digikey.com/u/yrrah53)\ **Post date:** [July 28, 2022, 9:10am UTC](https://forum.digikey.com/t/bbb-bullseye-22-07-01-pwm-does-not-work/24223/1 "2022-07-28T09:10:56Z")
Hello, I have recently updated my BBB to Debian Bullseye XFCE Image 2022-07-01. Serial I/O works but my application nicely running on older images gives errors when addressing pwm pins. My test script: import Adafruit\_BBIO.PWM as pwm pwm.start(“P8\_13”,50) pwm.start(“P8\_19”,60) pwm.stop(“P8\_13”) pwm.stop(“P8\_19”) Gives the famous: RuntimeError: Unknown error. for line 2 I can run config-pin commands without problem. Running the Python testscript in sudo or not does not make a difference. Please advise, Best regards, Harke ---
**Author:** ![RobertCNelson](https://sea2.discourse-cdn.com/digikey/user_avatar/forum.digikey.com/robertcnelson/32/12_2.png) [@RobertCNelson](https://forum.digikey.com/u/RobertCNelson)\ **Post date:** [July 28, 2022, 1:11pm UTC](https://forum.digikey.com/t/bbb-bullseye-22-07-01-pwm-does-not-work/24223/2 "2022-07-28T13:11:20Z")
> [@yrrah53](#): > > import Adafruit\_BBIO.PWM as pwm > pwm.start(“P8\_13”,50) > pwm.start(“P8\_19”,60) > pwm.stop(“P8\_13”) > pwm.stop(“P8\_19”) Adafruit\_BBIO has not been ported to v5.10.x-ti… As long as you load the pwm overlay, you can echo those values into /dev/bone/pwm/\* Regards, ---
**Author:** ![yrrah53](https://avatars.discourse-cdn.com/v4/letter/y/8797f3/32.png) [@yrrah53](https://forum.digikey.com/u/yrrah53)\ **Post date:** [July 28, 2022, 2:33pm UTC](https://forum.digikey.com/t/bbb-bullseye-22-07-01-pwm-does-not-work/24223/3 "2022-07-28T14:33:54Z")
Hello Robert, thanks. I am afraid I am not sure what it means… Regards, Harke ---
**Author:** ![RobertCNelson](https://sea2.discourse-cdn.com/digikey/user_avatar/forum.digikey.com/robertcnelson/32/12_2.png) [@RobertCNelson](https://forum.digikey.com/u/RobertCNelson)\ **Post date:** [July 28, 2022, 3:02pm UTC](https://forum.digikey.com/t/bbb-bullseye-22-07-01-pwm-does-not-work/24223/4 "2022-07-28T15:02:08Z")
Hi @yrrah53 first, there’s one package in 2022-07-01 that needs an update and it’ll be available in next week’s image with 2022-08-01… Default: 2022-07-01 ```auto debian@BeagleBone:~$ tree /dev/bone/ /dev/bone/ ├── i2c │ ├── 0 -> ../../i2c-0 │ ├── 1 -> ../../i2c-1 │ └── 2 -> ../../i2c-2 ├── spi │ ├── 0.0 -> ../../spidev0.0 │ ├── 0.1 -> ../../spidev0.1 │ ├── 1.0 -> ../../spidev1.0 │ └── 1.1 -> ../../spidev1.1 └── uart ├── 0 -> ../../ttyS0 ├── 1 -> ../../ttyS1 ├── 2 -> ../../ttyS2 ├── 3 -> ../../ttyS3 ├── 4 -> ../../ttyS4 └── 5 -> ../../ttyS5 3 directories, 13 files ``` First update bb-customizations package and enable it’s service file: ```auto sudo apt update sudo apt install --only-upgrade bb-customizations sudo systemctl enable bb-symlinks.service ``` Then reboot… ```auto sudo reboot ``` Now you will see the pwm symlinks… ```auto debian@BeagleBone:~$ tree /dev/bone/ /dev/bone/ ├── am335x │ └── ecap │ ├── 0 -> /sys/class/pwm/pwmchip0/pwm0 │ ├── 1 -> /sys/class/pwm/pwmchip1/pwm0 │ └── 2 -> /sys/class/pwm/pwmchip2/pwm0 ├── counter │ ├── counter0 -> /sys/bus/counter/devices/counter0 │ ├── counter1 -> /sys/bus/counter/devices/counter1 │ └── counter2 -> /sys/bus/counter/devices/counter2 ├── i2c │ ├── 0 -> ../../i2c-0 │ ├── 1 -> ../../i2c-1 │ └── 2 -> ../../i2c-2 ├── pwm │ ├── 0 │ │ ├── a -> /sys/class/pwm/pwmchip3/pwm0/ │ │ └── b -> /sys/class/pwm/pwmchip3/pwm1/ │ ├── 1 │ │ ├── a -> /sys/class/pwm/pwmchip5/pwm0/ │ │ └── b -> /sys/class/pwm/pwmchip5/pwm1/ │ └── 2 │ ├── a -> /sys/class/pwm/pwmchip7/pwm0/ │ └── b -> /sys/class/pwm/pwmchip7/pwm1/ ├── spi │ ├── 0.0 -> ../../spidev0.0 │ ├── 0.1 -> ../../spidev0.1 │ ├── 1.0 -> ../../spidev1.0 │ └── 1.1 -> ../../spidev1.1 └── uart ├── 0 -> ../../ttyS0 ├── 1 -> ../../ttyS1 ├── 2 -> ../../ttyS2 ├── 3 -> ../../ttyS3 ├── 4 -> ../../ttyS4 └── 5 -> ../../ttyS5 22 directories, 13 files ``` Next, from: [Beagleboard:BeagleBone cape interface spec - eLinux.org](https://elinux.org/Beagleboard:BeagleBone_cape_interface_spec#PWM) we see: ```auto P8_13 -> /dev/bone/pwm/2/b P8_19 -> /dev/bone/pwm/2/a ``` Now let’s configure, P8\_13 & P8\_19 for pwm output: ```auto debian@BeagleBone:~$ config-pin -l P8_13 Available modes for P8_13 are: default gpio gpio_pu gpio_pd gpio_input pwm debian@BeagleBone:~$ config-pin -l P8_19 Available modes for P8_19 are: default gpio gpio_pu gpio_pd gpio_input pwm ``` ```auto debian@BeagleBone:~$ config-pin P8_13 pwm Current mode for P8_13 is: pwm debian@BeagleBone:~$ config-pin P8_19 pwm Current mode for P8_19 is: pwm ``` Then go under /dev/bone/pwm/2/b and /dev/bone/pwm/2/a and configure your pwm device! ```auto debian@BeagleBone:/dev/bone/pwm/2/b$ tree . ├── capture ├── duty_cycle ├── enable ├── period ├── polarity ├── power │ ├── async │ ├── autosuspend_delay_ms │ ├── control │ ├── runtime_active_kids │ ├── runtime_active_time │ ├── runtime_enabled │ ├── runtime_status │ ├── runtime_suspended_time │ └── runtime_usage └── uevent 1 directory, 15 files ``` at a minimal, you need duty\_cycle, period, and enable… Regards, ---
**Author:** ![yrrah53](https://avatars.discourse-cdn.com/v4/letter/y/8797f3/32.png) [@yrrah53](https://forum.digikey.com/u/yrrah53)\ **Post date:** [July 28, 2022, 7:17pm UTC](https://forum.digikey.com/t/bbb-bullseye-22-07-01-pwm-does-not-work/24223/5 "2022-07-28T19:17:06Z")
Thank you Robert, can’t wait to download the next version… It all works like you wrote. But how can I change the value of enable, duty\_cycle and period? I am not a programmer, I am a ham using a Beaglebone to control my EME antenna. my best, Harke ---
**Author:** ![RobertCNelson](https://sea2.discourse-cdn.com/digikey/user_avatar/forum.digikey.com/robertcnelson/32/12_2.png) [@RobertCNelson](https://forum.digikey.com/u/RobertCNelson)\ **Post date:** [July 28, 2022, 7:33pm UTC](https://forum.digikey.com/t/bbb-bullseye-22-07-01-pwm-does-not-work/24223/6 "2022-07-28T19:33:33Z")
> [@yrrah53](#): > > It all works like you wrote. But how can I change the value of enable, duty\_cycle and period? I am not a programmer, I am a ham using a Beaglebone to control my EME antenna. [https://docs.kernel.org/driver-api/pwm.html#using-pwms-with-the-sysfs-interface](https://docs.kernel.org/driver-api/pwm.html#using-pwms-with-the-sysfs-interface) > When a PWM channel is exported a pwmX directory will be created in the pwmchipN directory it is associated with, where X is the number of the channel that was exported. The following properties will then be available: > > period > The total period of the PWM signal (read/write). Value is in nanoseconds and is the sum of the active and inactive time of the PWM. > > duty\_cycle > The active time of the PWM signal (read/write). Value is in nanoseconds and must be less than the period. > > polarity > Changes the polarity of the PWM signal (read/write). Writes to this property only work if the PWM chip supports changing the polarity. The polarity can only be changed if the PWM is not enabled. Value is the string “normal” or “inversed”. > > enable > Enable/disable the PWM signal (read/write). > > 0 - disabled > > 1 - enabled On the board, just run: ```auto debian@BeagleBone:/dev/bone/pwm/2/b$ echo 1000 > period debian@BeagleBone:/dev/bone/pwm/2/b$ echo 500 > duty_cycle debian@BeagleBone:/dev/bone/pwm/2/b$ echo 1 > enable ``` as one example… Regards,