C code to blink an LED on the BeagleBone, using the PRU microcontroller.

main.c

/*
 * blink demo: blink LED ten times
 * LED should be connected to P8_11 (pr1_pru0_pru_r30_15)
 *
 */
volatile register unsigned int __R31, __R30;

int main(void) {
    unsigned int loops, delay;
    for (loops = 0; loops < 10; loops++) {
        __R30 = __R30 | (1 << 15); // Turn on the LED
        for (delay = 0; delay < 20000000; delay++) { // loop delay
        }
        __R30 = __R30 & ~(1 << 15); // Turn off the LED
        __delay_cycles(60000000); // Intrinsic method delay
    }

    // Send interrupt to host and halt
    __R31 = 32 | 3;
    __halt();
    return 0;
}