For any other BeagleBoard beginners out there, here is a C program to toggle the usr LEDs, adapted from/inspired by this discussion:
http://groups.google.com/group/beagleboard/browse_thread/thread/db4accfabf02d986/872c61d84ea5a1a1
/*
* Toggles the usr1 LED once/second on the BeagleBoard.
* In the /sys/class/leds/beagleboard::usr1 directory, the brightness file controls usr1.
* To turn the LED on, write "1" to the file.
* To turn the LED off, write "0" to the file.
* To do the same for usr0, replace beagleboard::usr1 with beagleboard::usr0.
*/
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char** argv)
{
FILE *led_control;
char led_value[2] = "0";
printf("Blinking usr1 LED.\n");
printf("Press CTRL+C to end.\n");
while(1)
{
if ((led_control = fopen("/sys/class/leds/beagleboard::usr1/brightness", "r+")) == NULL)
{
printf("Can't open brightness file.\n");
exit(1);
}
if (strcmp(led_value, "0") == 0)
{
strcpy(led_value, "1");
}
else
{
strcpy(led_value, "0");
}
fwrite(&led_value, sizeof(char), 1, led_control);
fclose(led_control);
sleep(1);
}
return 0;
}