21 Feb 2015
If you are familiar with linux, you may know that everything in linux is a file. You can talk to a hardware as if you are writing to a file.
There are 4 on board LEDs in BBB. You can play with that LED.
Go to /sys/class/leds/beaglebone:green:usr3/
cd /sys/class/leds/beaglebone:green:usr3/
If you write a '1' to the file corresponding to LED3, then it will light that LED. Writing '0' will switch off the LED.
echo 1 > brightness
It will switch on the LED forever. :-) If you want to switch off it again type
echo 0 > brightness
Let's do it in c.
First ssh into your BBB (refer here). Then create a directory to work with.
mkdir helloworld
cd helloworld
Open your favourite texteditor.
nano LEDBlink.c
Then type this program.
#include<stdio.h>
int main()
{
FILE *LEDHandler=NULL;
char *LEDPath="/sys/class/leds/beaglebone:green:usr3/brightness";
if(LEDHandler=fopen(LEDPath,"r+")){
fwrite("1", 1, 1,LEDHandler);
fclose(LEDHandler);
}
sleep(3);
if(LEDHandler=fopen(LEDPath,"r+")){
fwrite("0", 1, 1,LEDHandler);
fclose(LEDHandler);
}
return 0;
}
Save the program using Cntrl+O and close it using Cntrl+X.
Then compile the program using
gcc LEDBlink.c
Then run your first program.
./a.out
The program will switch on the LED for 3s and then switch off.
There are 4 on board LEDs in BBB. You can play with that LED.
Go to /sys/class/leds/beaglebone:green:usr3/
cd /sys/class/leds/beaglebone:green:usr3/
If you write a '1' to the file corresponding to LED3, then it will light that LED. Writing '0' will switch off the LED.
echo 1 > brightness
It will switch on the LED forever. :-) If you want to switch off it again type
echo 0 > brightness
Let's do it in c.
First ssh into your BBB (refer here). Then create a directory to work with.
mkdir helloworld
cd helloworld
Open your favourite texteditor.
nano LEDBlink.c
Then type this program.
#include<stdio.h>
int main()
{
FILE *LEDHandler=NULL;
char *LEDPath="/sys/class/leds/beaglebone:green:usr3/brightness";
if(LEDHandler=fopen(LEDPath,"r+")){
fwrite("1", 1, 1,LEDHandler);
fclose(LEDHandler);
}
sleep(3);
if(LEDHandler=fopen(LEDPath,"r+")){
fwrite("0", 1, 1,LEDHandler);
fclose(LEDHandler);
}
return 0;
}
Save the program using Cntrl+O and close it using Cntrl+X.
Then compile the program using
gcc LEDBlink.c
Then run your first program.
./a.out
The program will switch on the LED for 3s and then switch off.
