// Macro for accessing a hardware register (32 bit)
#define HWREG(x) (*((volatile unsigned int *)(x)))

volatile register unsigned int __R31;

int finish = 0;

int main(int argc, const char *argv[]){
   volatile unsigned int* gpio1_dataout;
   // Enable OCP so we can access the whole memory map for the
   // device from the PRU. Clear bit 4 of SYSCFG register
   HWREG(0x26004) &= 0xFFFFFFEF;

   // GPIO1[21] as an output
   HWREG(0x44e10854) = 0x0f;

   // GPIO1[15] as an output
   HWREG(0x44e1083c) = 0x0f;

   // GPIO1[14] as an output;
   HWREG(0x44e10838) = 0x0f;

   gpio1_dataout = (unsigned int*)(0x4804c000+0x13c);

   while(!finish){
      int i;

      for (i=0; i<2000000; i++);
      *gpio1_dataout |= 1<<21;
      *gpio1_dataout |= 1<<15;
      *gpio1_dataout |= 1<<14;
      for (i=0; i<2000000; i++);
      *gpio1_dataout &= ~(1<<21);
      *gpio1_dataout &= ~(1<<15);
      *gpio1_dataout &= ~(1<<14);

      __R31 = 35;
   }

   // stop pru processing
   __halt();

   return 0;
}