PWM in beagle bone black

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1

Hi,

I am recently working on Beagle bone black, i need to use PWM module in the beagle bone black.

i followed the bellow steps for configuration :

  1. cd /sys/class/pwm
  2. ls → here i found pwmchip0, pwmchip1, pwmchip2, pwmchip3…pwmchip7.
  3. cd pwmchip0
  4. ls → here i found : device export npwm power subsystem uevent unexport.
  5. echo 0 > export i added pwm0
  6. ls → i can see pwm is added.
  7. cd ./pwm0 → here i can see the duty cycle , period and other information.

i want to add the pinmux for pwm

debian@beaglebone:/sys/class/pwm$ config-pin -l P9.22
default gpio gpio_pu gpio_pd gpio_input spi_sclk uart i2c pwm pru_uart
debian@beaglebone:/sys/class/pwm$ config-pin P9.22 pwm
P9_22 pinmux file not found!
sudo: no askpass program specified, try setting SUDO_ASKPASS
Cannot write pinmux file: /sys/devices/platform/ocp/ocp*P9_22_pinmux/state

but it is showing error for adding P9.22 pin as pwm.

please help me to resolve it

2

In other hand if i try to add some more pwm means it is showing the error like this

debian@beaglebone:/sys/class/pwm$ cd pwmchip0
debian@beaglebone:/sys/class/pwm/pwmchip0$ ls
device export npwm power pwm-0:0 subsystem uevent unexport
debian@beaglebone:/sys/class/pwm/pwmchip0$ echo 3 > export
-bash: echo: write error: No such device

i am not able to add other pwm module… why it is showing the error.

please resolve it…

3

Insiders tip welcome?

Check out libpruio for easy and powerful PWM (and pinmuxing) features.

Regards

4

Hi,

can anybody suggest me c programing example on the pwm in beagle-bone black.

5

https://stackoverflow.com/questions/29369616/beaglebone-black-pwm-using-c

6

Hi,

using pwm i am doing some configuartions in the beaglebone black…

in /sys/class/pwm/pwmchip1

7

Hi,

using pwm i am doing some configurations in the beagle bone black…

in /sys/class/pwm/pwmchip1

echo 0 > export
echo 1 > export

i can see the 2 pwm are added pwm1:0 , pwm1: 1

using cd pwm1:0 i am assigning the duty cycle , period and enable

if i rebooted the BBB means this configurations are erasing, why i am not getting??

using config-pin -l P9.14

config-pin P9.14 pwm

i am setting pin for pwm as p9.14

in hardware wise i am connecting 1 external led providing 1 connection from P9.14 and other end to ground.

but led should glow based on pwm duty-cycle, but here the LED not all glowing ???

please suggest me where i am missing??

8

Hi ,

i am using kernel version of 4.14.so slots file and bone -capemgr are disabled in V4.14 of kernel in the favor of U-boot overlay.

my uEnv.txt file look like this.

debian@beaglebone:/boot$ cat uEnv.txt
#Docs: http://elinux.org/Beagleboard:U-boot_partitioning_layout_2.0

uname_r=4.14.71-ti-r80
#uuid=
#dtb=

###U-Boot Overlays###
###Documentation: http://elinux.org/Beagleboard:BeagleBoneBlack_Debian#U-Boot_Overlays
###Master Enable
enable_uboot_overlays=1

9

Isn't this just a permission error? Does it work with sudo?

10

Hi,

I got why that error is coming . already i used those pins to UART , so i can’t use that pins again to PWM.

i am using P9.14 for pwm, but still also it is not working for me…

i am feeling something i need to add in to uEnv.txt, but i am not getting …

please suggest me??

11

Hi Megha,

I recomend you to use adafruit python library to check your uEnv.tx configuration and pin choice. It is a very easy to use lib and helped me a lot to test GPIO stuff.

Here is a link to a simple tutorial:https://learn.adafruit.com/setting-up-io-python-library-on-beaglebone-black/pwm

12

Hi Luis!