How to on and off the leds which are connected on lpc3250 board

Hi,

I am working on kernel version 2.6.34 in ubuntu 11.10 with LPC3250 board.I loaded the boot loaders kickstart,stage1 and u-boot loaders in my board. In my board leds are connected to P2^0 and P2^1 pins and I have enabled the "LED Support for GPIO connected LEDs" in "LED SUPPORT" option of kernel menuconfiguration. Now i want to
make ON and OFF operations for these LEDS and is any application have to write to perform this operation?Please help me how to make that operation?

Thanks & Regards,
Md.biyabani.

If you have correctly enabled the LEDs, you can cd to /sys/class/leds/ where you should be able to see several directories. For instance, on a ThinkPad laptop, I can see several led directories that look like this:
/sys/class/leds/tpacpi\:thinklight, when I cd to that directory I see several files, one of which is called "brightness". To check the current setting I type: cat brightness which returns "0" indicating the led is off. To turn on the led I type: echo 100 > brightness and the led turns on.

Thanks for your reply.The sys directory not found in my application after kernel booted. It contains the directories as below


### Application running ...
~ # ls
bin etc home linuxrc sbin usr
dev ftp lib proc tmp var

Where i will get that sys dir?

Thanks & Regards,
Md.biyabani

I admit, you have confused me. The /sys filesystem is actually a pseudo file system that is part of the linux kernel from 2.6 on (as far as regular releases go). Wat version of the kernel are you running ? If you could execute the command : uname -a and include the output in your next reply it may help.

Thanks for your Reply. The output of you mentioned command in application after kernel booted is

~ # uname -a
Linux 192.168.1.19 2.6.34 #59 PREEMPT Wed May 1 14:35:51 IST 2013 armv5tejl unkn


After that i type the below command and got the output is

~ # ls
bin etc home linuxrc sbin usr
dev ftp lib proc tmp var

It is not showing any sys directory. I hope this information is useful to help me.

Thanks & Regards,
Md.biyabani.

Since I am not familiar with your LPC3250 evaluation board, I can't know for sure, but are there jumpers or control registers that need to be properly set to enable LED control via the GPIO pins? I am completely puzzled about the lack of a /sys filesystem since I have never worked on a system with a 2.6.x kernel where that was unavailable. Is it possible that you are mounting an NFS filesystem and the listing you have shown me is from that? I am sorry, but I am running out of ideas.

Regards

Another thought I just had. I noticed that the prompt you were showing: ~ # ls is NOT the filesystem root (the '~' means you are in the logged in user's home directory), so try this:
cd /
ls -l

Let me know if this works

Regards

Hi,

@OP biyabani

You can always use 'pwd' on command line to show the working directory;

excerpt from 'man pwd'; NAME pwd - print name of current/working directory SYNOPSIS pwd [OPTION]... DESCRIPTION Print the full filename of the current working directory. -L, --logical use PWD from environment, even if it contains symlinks -P, --physical avoid all symlinks --help display this help and exit --version output version information and exit NOTE: your shell may have its own version of pwd, which usually supersedes the version described here. Please refer to your shell's documentation for details about the options it supports.

Just a few links to aid you to gaining some understanding; Linux Documentation Project Rute Tutorial & Exposition Linux Command Guide Utimate Linux Newbie Guide LinuxSelfHelp Bash Beginners Guide Bash Reference Manual Advanced Bash-Scripting Guide Linux Home Networking The above links and others can be found at 'Slackware-Links'. More than just Slackware® links!

Above links should help you to learn. Hope this helps.

Thanks for reply to all..

Previously posted directories are before mounting NFS and that is,
~ # ls
bin etc home linuxrc sbin usr
dev ftp lib proc tmp var

I tried this also

~ # cd /
~ # ls -l
drwxr-xr-x 2 1543 1543 3072 Nov 24 2008 bin
drwxr-xr-x 2 root root 3072 Nov 24 2008 dev
drwxr-xr-x 5 1543 1543 1024 Jan 1 00:00 etc
drwxr-xr-x 2 1543 1543 1024 Nov 24 2008 ftp
drwxr-xr-x 2 1543 1543 1024 Nov 24 2008 home
drwxr-xr-x 3 1543 1543 1024 Nov 24 2008 lib
lrwxrwxrwx 1 1543 1543 14 Nov 24 2008 linuxrc -> ../bin/busybx
dr-xr-xr-x 35 root root 0 Jan 1 00:00 proc
drwxr-xr-x 2 1543 1543 1024 Nov 24 2008 sbin
drwxr-xr-x 2 1543 1543 1024 Jan 1 00:00 tmp
drwxr-xr-x 4 1543 1543 1024 Nov 24 2008 usr
drwxr-xr-x 4 1543 1543 1024 Nov 24 2008 var

And after mounting the NFS

~ # mkdir nfs
~ # ls
bin etc home linuxrc proc tmp var
dev ftp lib nfs sbin usr
~ # mount -t nfs -o nolock 192.168.1.10:/home/mohan/nfs /nfs
~ # ls
bin etc home linuxrc proc tmp var
dev ftp lib nfs sbin usr

In the above procedure i didnot found any SYS dir. is there any other kernel version that may contains this Directory?

Please give reply if you get any idea about it.

Thanks & Regards,
Md.Biyabani.

Hi,

I spent a few minutes using these guides which are good references;

http://www.embeddedartists.com/sites...sers_Guide.pdf

http://embedded.lectoraat.org/uww/PD...BSP_Manual.pdf
If you followed the setup in above link then the root is: rootpath=/home/user/ltib/rootfs

section 2.6 Load the Root File System and Linux Kernel See page 11 of this link: http://embedded.lectoraat.org/uww/PD...BSP_Manual.pdf

Above section does show that a /proc & /sys are loaded via busybox. I did not look at the Fedora or Ubuntu loads but I think you use a VM Appliance for Ubuntu. Not having a physical board to verify/debug that indeed uboot is used to init & load Linux Kernel with the command: 'uboot> run mtdboot'. 'mtdboot' would be the image on your stick/sd that must be setup via tools;

The Linux Target Image Builder (LTIB) system will be used to build the u-boot, Linux kernel and root file system. LTIB ease the build and deployment process of several components needed in a Linux system. Besides the bootloader and kernel a lot of needed utilities, modules and libraries are included and will be configured and built automatically by LTIB. For more information about LTIB, go to http://ltib.org

Most ARM systems do use these techniques to utilize Linux on their boards.