Can't acces to the PWM output on Jetson TK1

Autonomous Machines Jetson & Embedded Systems Jetson TK1
1

OK, going straight to the point. The Jetson comes with PWM outputs. However when I try to access them, it tells me “Permission Denied”. I’m following The guidelines from http://elinux.org/Jetson/GPIO.

CONFIG_PWM_SYSFS=y

The guidelines says the following

Note: In the L4T kernel, the “soc0” directory component might not be there, and the PWM controller might be named something different like “pwm.0” or “pwm.1”. You might want to just run:

cd /sys
find . –type d –name "pwmchip*"

However. When I try the command line cited above, the Jetsons gives the following

find: './kernel/debug': Permission denied

Any clue about what am I doing wrong? What am I missing?

Thanks beforehand,
Anfedres

2

Did you use root permissions? sudo each command, or “sudo -s” and continue. Files controlling system operation are restricted and not open to every account in the world. Pretty much everything that does something interesting requires sudo for an Ubuntu distribution.

3

Would you mind to give me an example in how I can use it? I’m a newbie on this. The only thing I know is that I’m accessing as an administrator.

4

OK. I did what you suggested “sudo -s” and the other command lines. However, it does not give a proper answer. I want to know which are the pins at the GPIO I can assign as PWM.

root@tegra-ubuntu:/sys# find . –type d –name "pwmchip*"
root@tegra-ubuntu:/sys#

Thanks.

5

Many of the I/O pins are used by more than one function, with only 1 enabled at a time. Even that article mentions setting up PINMUX and being sure that the GPIO is not taking over that pin. In terms of the actual PWM files in /sys, these are kernel features…those files do not exist unless the kernel feature exists. The article refers to this:

CONFIG_PWM_SYSFS=y

…which is a feature one has to enable and use from a custom compiled kernel. There are several threads on this forum regarding kernel compile and installation. You can practice and try configuring and building kernels with no risk. When satisfied, you can ask more questions on installation options.

6

I see another old thread on this topic which may be of interest. Apparently there is a kernel version issue as to whether sysfs file options exist:
[url]Jetson TK1 PWM output - Jetson TK1 - NVIDIA Developer Forums

7

PWM to work you must also modify the DTB files, The Grinch Kernel support PWM output

8

Santyago, I am considering purchasing the Jetson K1 motherboard for my HTPC setup: I currently will need it to be able to stream Youtube videos and other Flashplayer videos. Also, i will need it to receive internet through a wireless USB or mini-PCI-e fitting.

  1. How do i get it to stream Youtube? Is it simple install through the Chrome app for Linux?
  2. What wireless device is best to use with-out much trouble shooting? Can be USB or mini-PCI-e
9

One solution for watching youtube videos might be the Kodi (XBMC), I think it has Youtube plugins/add-ons.

There is a separate thread about mini-PCIe WIFI cards. You may want to check it through and pick a card that is proven to work with the Grinch kernel.

10

Hello,
How can i access GPIO without using Sudo?
Thanks KT